Science behind your garden

The home gardener is part scientist,
part artist, part philosopher, part ploughman.
– John R Whiting

Science behind your Garden is a new internet resource for home gardeners.
The information has been written with the home gardener in mind, providing an understanding of the fascinating science behind gardening.

It covers the all-important role of water, soil, nutrients and the microscopic bugs that live in soil. It provides information on some of the most frequently grown plants, taking an integrated approach that enables you to manage your garden in balance with the environment. The areas covered are:

Table of contents
This site is hosted by New Zealand Plant Producers Incoporated and utilises material originally developed by the former New Zealand Institute for Crop and Food Research Limited and the Horticulture and Food Research Institute of New Zealand and others.
Contact us www.nzppi.co.nz

If you want a brief introduction to a topic, try Quick facts. For more detailed information, More info is for you.

For a start, read about the principles behind managing your garden in balance with the environment, or about how plants are named.

Integrated Garden Management (IGM)

Few people make a full-time living from their home garden, so it follows that most gardeners have other reasons for following this pastime. For some it is a hobby, many want to create a peaceful living environment while others want to save money and produce nutritious food. Despite these vastly differing objectives everyone wants healthy plants in their garden. This is where integrated garden management (IGM) comes in.
Ever since humans changed from being hunter-gatherers to actively farming plants and animals for food and other necessities, people have looked for ways to increase yields, improve quality or to reduce the effects of pests and diseases. Over the past several hundred years this has become an occupation for some people – the scientists who spend their lives studying certain plants or animals and looking at ways to get better returns from farming.

Towards the end of the 20th century, scientists in New Zealand began to pool their knowledge and develop packages for managing certain crops. This arose out of the need to decrease reliance on chemical control of pests and diseases and became known as integrated pest management (IPM). A technical definition of IPM is “the control of pests by employing all methods consistent with economic, ecological and toxicological requirements while giving priority to natural limiting factors and economic thresholds”.

The IPM packages developed by scientists for farmers can also be utilised by home gardeners. The concept behind IGM is to use a range of approaches to ensure that plants remain healthy and the effects of pests and diseases are limited. IGM principles are often even more relevant for home gardeners than commercial growers, since people are often very concerned about maintaining a healthy environment around their home and also have a greater tolerance to damage caused by pests and diseases than many of our export markets!

IGM involves a range of techniques, not all of which are relevant for every plant being grown in the home garden. In fact, some techniques beneficial to some plants and in some situations may be harmful to other plants and in other conditions. Like most things in life, it is all a question of balance! Some of the most common IGM techniques are discussed below and more information is available in the sections on specific plants.

Prevention

The first step in IGM is always to prevent a pest or disease from getting into the garden. Some of the techniques listed below will help with prevention, like disposing of diseased plants by burying or burning so that subsequent crops are not infected. Always buy healthy plants and certified seeds to ensure that new diseases or insects are not brought into the garden.

Identification

Observe your plants closely. Watch for distorted growth, wilting or yellowing. These are all signs that the plant is not healthy. Is this caused by a disease, an insect pest or perhaps something wrong with the soil? Look up books, use the internet or ask an expert at a garden centre to help with the diagnosis. Often if a problem is identified early enough then a solution can be found.

Crop rotation

Many pests and diseases are specific to one crop. By changing the position in the garden that the crop is grown in every year these diseases can be limited, as the new crop is not reinfected from the soil or previous crop residues. For example, nematodes and powdery scab that infect potatoes may survive in the soil or on tubers remaining from the previous crop. In the ornamental garden it is often advisable to plant a different species when replacing a plant that has died.

Improved soil fertility can be another benefit of crop rotation in the vegetable garden. Leguminous plants, such as peas and beans, have root nodules containing bacteria that fix nitrogen. The nitrogen fixation process makes atmospheric nitrogen available to the growing plant and may also increase the level of soil nitrogen available to subsequent crops.

Resistant cultivars

One of the best methods of limiting the effects of pests and diseases is to grow resistant plants. In this situation the resistant plants are not infected or they can tolerate the pest or disease without major losses in yield or quality. Much of the effort in plant breeding programmes is directed towards selecting for pest and disease resistant plants. Where possible choose cultivars that are resistant to pests and diseases. For example, the sugar pea Snow Queen is resistant to powdery mildew, while the floribunda rose Iceberg is known for having disease-free foliage.

Planting and harvesting date

In the vegetable garden planting and harvesting dates can be adjusted to avoid the times when pests and diseases are at their worst. For example, delaying planting of potatoes until soil temperatures have risen will help prevent powdery scab damage, while it is advisable to harvest carrots before the period of peak flight activity (April-early May) of carrot rust fly.

Clean seed and healthy plants

It is a good idea to buy seed that has been certified free of diseases. Some home gardeners prefer to harvest their own seed but make sure that the parent plant is healthy. When buying plants for the garden look at them carefully to make sure you are not bringing new pests or diseases into your garden!

Soil preparation

Before sowing seeds or a potted plant, make sure the ground is well prepared. This includes providing good drainage, supplying appropriate fertiliser (which may include adjusting the pH) and ensuring the soil is well aerated and not compacted. Research has demonstrated that peas growing in compacted soil are more likely to become infected by root rots, while camellias require neutral to acid soil.

Garden management and hygiene

It is well known that healthy plants are more resistant to pests and diseases than plants that are growing poorly. The garden needs regular maintenance and application of the IGM principles. This need not take a lot of time – a nightly stroll round the garden can reveal an area that has not been watered or some tomatoes than fertiliser. Diseased leaves of roses can be picked off and disposed of by burial or burning.

Weed control

Plants may be weakened and become more susceptible to pests and diseases if they have to compete with weeds for moisture and nutrients. In addition some weeds harbour pests or diseases that are transmitted to ornamental or crop plants. For example, hemlock can harbour leaf blights or spots that can infect carrots. So remember that weeding isn’t just to make the garden look good!

Fertilisers and irrigation

Plants that don’t have sufficient fertiliser or water won’t produce good yields and they are more likely to be affected by pests and diseases than healthy plants. However, ensure that the correct fertiliser is being applied and don’t over-water. For example, Aphanomyces root rot is frequently found in peas growing in wet soils, while excessive nitrogen fertiliser on potatoes can lead to increased levels of bacterial soft rot.

Biological control

Biological control is when an organism is used to minimise the effects of another organism that is a pest or disease to the crop or ornamental plant. It is important that the beneficial organism does not damage the target or surrounding plants. Insects, micro-organisms and plants can be used for biological control. A common example of biological control is ladybirds eating aphids. The beneficial organism can be artificially reared and released or the home gardener can create conditions in the garden that will encourage the presence of the beneficial organisms. This may include minimising the use of damaging sprays or companion planting, which is described below.

Companion planting

A practice much loved by organic gardeners, the science behind companion planting is only just beginning to be revealed. The theory is that companion plants produce compounds that attract beneficial organisms or repel organisms that are pests or diseases. For example, nasturtiums produce a mustard oil that aphids dislike. Another good companion plant is buckwheat, which produces nectar to feed parasitic wasps. Although the wasps sound rather nasty, the are quite small and only attack insects such as leafroller caterpillars.

Chemical control

If all else fails it may be necessary to use chemical sprays or dusts. Some chemicals are more selective than others, which means that only the target pests or diseases are affected. These chemicals should always be used rather than the “broad spectrum” chemicals that may affect beneficial organisms as well as the targets. Always read the directions carefully and follow them. Increasing the rate of chemical is not a substitute for correct application. If repeated applications are required, try and use a chemical from a different chemical group to avoid the build-up of resistance within the pest or disease population. Note that some chemical sprays and dusts, e.g. sulphur and Derris Dust®, are certified for organic use.

Naming plants

Why use Latin or scientific names for plants?

Many gardeners try to avoid the use of Latin or scientific names for plants as they find them long and difficult to pronounce. However, once the concept is understood, Latin names can actually be quite helpful for identifying plants. Scientific names for plants were originally developed because different common names are used for plants, depending on the region or language. For example, the invasive grass weed Elytrigia repens has the common names couch or twitch. Latin was the original language used in scientific literature and so it was decided to keep using it for scientific names. In addition, the Latin language is no longer spoken as a native language and is therefore unchanging, so Latin words do not take on new meanings or connotations.

Making sense of scientific names

To fully understand scientific names, we must briefly look at taxonomy, which is the study of classifying and naming organisms. Each living organism is classified into a series of groups or taxa, whic+h start with the five kingdoms and follow down through the phylum, class, order, family, genus and species. Carolus (Carl) Linnaeus (1707-1778) was a Swedish naturalist, who is credited with developing modern taxonomy. He designed the binomial (a Latin word meaning two names) system, whereby each species was identified by two words, the first being the genus name and the second a specific epithet, e.g. Lobelia erinus. The plant used in this example is a small annual with bronze leaves and deep blue flowers that are produced continuously from spring to autumn. However, the genus Lobelia includes other garden plants, such as Lobelia laxiflora, a perennial plant suited to tropical conditions with dark green leaves and red and yellow flowers that appear in summer.

The scientific name is always written in italics and the genus name is always capitalised (the specific epithet is in lowercase). Sometimes only the genus name is given. There are several reasons for this, such as the plant has been identified to the genus but not species level, e.g. Hosta sp., or the reference is to all the species in a particular genus, e.g. Rosa spp. (sp. and spp. are the singular and plural abbreviations for species). In addition, many garden plants have arisen from crosses of parent plants that are different species within the same genus. For example, many camellias are hybrids between Camellia japonica and C. saluenensis, and these are given a collective name preceded by a multiplication sign, e.g. Camellia x williamsii. Note that sometimes the genus name is abbreviated to the initial capital and a full stop, followed by the specific epithet, e.g. Camellia saluenensis was abbreviated to C. saluenensis in the previous sentence. This is only done when there is no chance of misinterpreting the abbreviation for another genus name.

A plant may be given a Latinised name after the person who first discovered it or someone who is prominent at the time. For example, the genus Fuchsia is named after the German physician and herbalist Leonhart Fuchs. Names can also be descriptive, particularly the specific epithet. For example, ruber (rubrum), sanguineus, roseus and coccineus refer to plants with red or pink colouration (e.g. Schizostylis coccinea has bright red flowers in autumn), lutea is for yellow colours and albus (alba) is white. Other names refer to fragrance (odorata or ororatum), flower shape or size (flora is Latin for flower so grandiflorium means big flower), leaf shape (folium or folia means leaf, so trifolium refers to three-leaved) and place of origin (novaeselandiae is from New Zealand and sinensis means Chinese, while borealis, australis, occidentalis and orientalis refer to northern, southern, western and eastern, respectively).

So when you next see a scientific name in a book or on a plant label, don’t dismiss it. Take a good look and see if you can work out something about the plant from the name. Also remember that much of the English language is derived from Latin so the pronunciation is very similar. Just break the word down into syllables as you would with a long English word.

Soil

Nutrients

Soil nutrients occur naturally in the soil and their presence and availability are without doubt major factors affecting both crop yield and quality. Plants growing on nutrient-deficient soils tend to be weak with low immunity, attracting pests and disease. Therefore, it is always best to keep soil fertility at a sufficient level rather than wait for signs of deficiency to occur, i.e. prevention is the best cure.

Fact

Most New Zealand soils are naturally deficient in phosphorus (P) and sulfur (S) because soil is developed from both melted bedrock and weathered bedrock, which were eroded under high rainfall conditions.

Soil pH

The pH of a soil will determine to a large extent the plants that can be grown on it. It can also affect the availability of nutrients, with some nutrients becoming inaccessible to plants at certain pH levels. However, by adding appropriate amounts of materials the pH of your soil can be adjusted.

Effect on plants and nutrient availability

Soil pH Impacts

7.5 Many flowering shrubs do well, but not the heather group, azaleas, rhododendrons, lupins, or most lilies. There is a reduced availability of phosphate, potassium, manganese, and iron.
6.0 - 6.5 Optimum for most plants. Maximum availability of mineral nutrients.Phosphates fixed by soil; potassium, calcium, magnesium, and trace elements suffer loss by leaching. Bacteria affected more than fungi.
< 5.5 Many plants suffer from acidity; roots short, stubby often fanged. Phosphate becomes less available.
4.0 Heaths and moorland plants and rhododendrons do well, but many other flowering plants fail. Soluble aluminium appears in harmful quantities.

Why and when plants need some major nutrients?

Positive effects	Prevalent time	Deficiency effects
    

Nitrogen (N)

The rate and vigour of growth and colour of leaves. Protein building, enzymes and photosynthesis

Occurs during early spring owing to the leaching effects of high rainfall and again in late summer when prolonged drought conditions result in soil nitrogen being trapped and concentrated in the dry surface soil above the absorptive root zone. (Pic) Stunted growth; small yellow, pale green or possibly bluish leaves. Thin weak stems.
Nitrogen deficient plant
(www.cropsoil.uga.edu)
Phosphorus (P)

Root growth, ripening of seeds and fruit. Phosphorus deficiencies are most pronounced in the winter and early spring when soil forms are immobile and relatively unavailable for growth.
(Pic) Stunted roots and growth. Small purple leaves and stems.
P deficient plant.
(www.worldinter.net)

Potassium (Potash or K)

Assists photo-synthesis and the production of carbohydrates. Protects plants against diseases and environmental stress.
May occur at any time of the year. It is easily leached from the soil and consequently deficiencies are common during periods of high rainfall.

Note: Close links with nitrogen. When nitrogen is increased, so must potash or deficiency will appear

(Pic) Fruits are poorly coloured, lacking in flavour. Leaves will appear scorched at edges, mottled, spotted or curled. K deficient leafs (www.cropsoil.uga.edu)

Methods of improving soil N, P and K levels

N (nitrogen), P (phosphorus) and K (potassium) are the nutrients that plants need in the largest quantities so it is a good idea to feed small amounts of fertiliser often, rather than large amounts infrequently because too much fertiliser can be lost to the air or groundwater.

Natural sources:

N – Hen manure, animal urine, green lucerne hey, fresh grass clippings and legume green manures (e.g. cereal straw residue).

P– all plant wastes, blood and bone, eggshells and animal manures.

K – most New Zealand soils have sufficient potassium reserves so returning plant residues to the soil prevents the need to apply other sources of K.

Gardeners be aware!

Not all plants have the same nutrient requirements so you must match fertiliser and/or compost application to a given soil with the needs of the plants that are to be grown in that soil. Oversupplying nutrients can harm the environment and sometimes be lethal.

Earthworms

Earthworms are segmented worms that are scientifically classified as belonging to the phylum Annelida (ringed animal). There are 3500-4000 species of earthworms around the world. They are full of calcium, protein, fibre and vitamins, making them a valuable food source for many mammals, reptiles and fish. Earthworms vary in size, ranging from 1 centimetre through to about 1metre in length. One of the world’s largest earthworms, the Giant Gippsland Earthworm (Megascolides australis), is found in Australia. It has an average length of over 1 metre.

Earthworms of New Zealand

There are nearly 200 different species of identifiable earthworms in New Zealand. Most of them are native but a few were accidentally introduced by early settlers from Europe in soil used as ship ballast as well as potted plants.

Native New Zealand earthworms are bigger and more vulnerable to disturbance than the introduced species, and they tend to populate less frequently disturbed areas.

Interesting fact

A New Zealander discovered that the total weight of all earthworms below a pasture is similar in weight to grazing animals supported above ground.

Different earthworms, different homes,
and different jobs

Earthworm species play different and unique roles in the soil environment.

There are four main types of earthworms in home gardens:

Compost dwellers. Like to live in high organic matter environments such as compost heaps, but will not usually survive in soil unless it has a very high organic matter content.
Soil surface dwellers. Feed on decaying roots, shoots, leaves and dung and live near the soil surface (0-15 cm depth). Important in mixing plant litter into the soil.
Topsoil dwellers. Most common earthworms in New Zealand; live in the top 20-30 cm depth of soil. Burrow through soil, eating and excreting it; tend to eat more soil than organic matter.
Subsoil dwellers. Tend to live in permanent burrows up to 3 m below the soil surface; drag food such as leaves into their burrows from the soil surface; often larger than other types of earthworms.

Earthworm biology

Earthworms wriggle underground with the help of tiny bristles (setae) along their outer surface and discharge a slimy lubricating mucous. Their strong muscles convey swallowed soil and organic residues (e.g. micro-organisms and partially decomposed plant and animal material) found on the soil surface to the gizzard. Stones that were swallowed and the strong muscles of the gizzard then grind up these materials and pass them through to the intestine where digestive juices act upon the material and release organic molecules such as amino acids and sugars. Some of this is absorbed into the bloodstream and the remainder, along with undigested waste, is excreted by worms as castings or ‘worm poop’.

Benefits of the mighty earthworm

Enhance soil fertility
Note: through digestion of organic matter Improve soil structure
Note: through movement and feeding
Incorporate surface litter and speed up nutrient recycling Increase the mixing of soil layers
Encourage mixing of nutrients, fertiliser, and lime through the soil profile Enhance water infiltration·
Increase nutrient availability to plants through digestive fluids together with increased microbial activity in the casts (droppings) Reduce erosion
Increase the decomposition rate of organic matter by burying around 6 tonnes of pasture litter per hectare· Increase plant growth Increase moisture holding capacity
Increase plant growth Increase plant growth by facilitating plant root penetration
Help control diseases, e.g. apple scab disease · Facilitate the break down of root mats in pastures and thick layers of leaf matter

Encouraging earthworms into gardens

Maintain soil pH between 5.8 and 6.3 by adding lime periodically to the soil.
Limit the amount of cultivation where possible. Avoid machines that pulverise the soil and the earthworms contained therein.
Use garden forks rather than spades.
Limit the use of harmful pesticides (particularly fungicides and fumigants).
Irrigate the soil during dry periods to maintain earthworm activity.
Increase organic matter in the soil by incorporating composted material or animal manure. Otherwise, earthworms will migrate if there is a lack of organic matter present.

water

Water is an essential source of life and, likewise, soil water is of vital importance for plant growth and survival. Soil can be described as a ‘leaky’ storage place for water. It leaks through evaporation, transpiration (water absorption by plant roots), run-off, and drainage. Hence the quantity of water left behind in the soil is available for use by plants, and is termed PAW, which stands for Plant Available Water.

What causes plants to wilt?

Plants need water to support them in an upright position. In the absence of PAW, the plant starts to wilt. At this point, if additional water is not supplied to the soil speedily, plant tissues will loose their ability to recover and these plants will die.

Storage of water in soil

Soils hold water in two different ways:

  1. within the soil organic matter, i.e. in dead and decaying plant and animal remains as well as the humus (partially decomposed organic soil material) in the soil;
  2. held in a thin film upon the surface of each of its mineral particles, i.e. sand, silt, and clay.

How do you improve soil water holding capacity?

Whether your garden soil has a greater proportion of sand or clay, there is a ready way to improve its water storage ability. The solution is adding more organic matter.

Organic matter

Can be added in the form of mulch (a thick layer of organic matter applied to the soil surface) and:

acts as an insulating layer
reduces surface evaporation of water from the soil surface
recycles nutrients back into the soil

Too much water is bad for your plants

Plant roots need air to breathe. As water drains through soil it takes fresh air down with it, renewing the air in the cavities and spaces between the soil particles and providing plenty of air for plant roots. However, if there is too much water for a prolonged period of time the plant roots will suffocate and the plant will die, unless the plant is of a type adapted to waterlogged conditions, e.g. water lilies.

How much water do I need to apply?

In general you only need to apply water during the months of spring (September-November) and summer (December-February), when the quantity of water evaporated from plants and soil (potential evapotranspiration (PET)) usually exceeds the quantity replaced by rain. The current levels of PET and rainfall are usually published in your local daily newspaper. See below for the method used to detect the levels of water you need to apply:

Total rainfall over a given time (e.g. week) –
Total PET over a given time (e.g. week)
= Amount of water needed to be applied at the end of a given time (e.g. week)
Note: As a rough guide, the maximum amount of water your garden needs per week is around 15 mm (rainfall plus irrigation) in October, and this will increase (dependent on weather conditions) up to about 35 mm (including rainfall plus irrigation) per week in December and January.

Can gardening cause water contamination?

YES! Over-watering that occurs when you let the water run too long or when water is applied faster than the ground can absorb leads to run-off and leaching (downward movement through the soil of a dissolved substance). Water run-off tends to contain soil, pesticides, and fertilisers that can contaminate our waterways and oceans. Leaching can contaminate ground water with fertilisers and pesticides.

Why be concerned?

Contaminants make water unsuitable for drinking (e.g. excess nitrate levels in drinking water caused blue-baby syndrome), recreation, agriculture and industry.
Residues from fertilisers can over stimulate aquatic plant growth, making the water unsuitable (e.g. depletes oxygen level in the water, reduces sunlight penetration) for fish and other aquatic life
Contaminated water can reduce or wipe out aquatic life by killing or reducing its reproductive ability.
Consumption of fish and other aquatic life from contaminated water can result in human heath risks

14 simple ways to save water

Water plants only when they really need it.
Hand water your plants whenever possible.
Check your soil and weather forecasts before watering your plants.
Avoid run-off by applying water slowly.
Water plants on calm days, either during the morning or the evening, and reduce water loss evaporation.
Reduce lawn areas and plant trees, shrubs, and groundcovers instead because lawns require more water.
Choose low water-use plants – ask your friendly garden shop assistant.
Apply mulches, grass clippings and straw to conserve ground moisture and discourage weeds from germinating.
Avoid using sprinklers if possible, because they result in water run-off. Instead use soaker hoses or drip irrigation.
Collect rainwater from your roof and use it to water your plants.
Avoid watering frequently in small amounts because they tend to make plants more susceptible to drought by encouraging shallow rooting.
Use low flow sprinklers.
Use a timer on irrigation systems.
Use an irrigation timer fitted with a ‘rain switch’ so that the sprinkler will automatically switch off when it detects rain.

Declaration for gardeners

Save our precious water by minimising water run-off from your land. In return, your garden will flourish with improved soil/plant health and reduced weed growth.

structure

Soil is an essential natural resource, formed spontaneously from rock over an extensive period of time, and made up of soil solids (mineral particles and organic matter) and pore spaces filled with water and air.

Soil profile

Soil is made up of several distinct layers or horizons. These layers form what is known as the soil profile.

The top layer of soil or topsoil is the richest, having the most amount of humus (partially decomposed organic soil material). This phenomenon is largely due to the presence of decomposers (predominantly bacteria, fungi, and earthworms) that recycle dead organic matter (plants and animals) into humus. The subsoil is below the topsoil and is low in humus. However, this is where most soil nutrients are found. Below the subsoil is weathered parent material, which is full of rock particles and minerals with no humus. Parent material is the initial state of soil and can be bedrock, organic material or deposits from water, glaciers, volcanoes, or wind. Physical weathering over millions of years has broken down these materials into fine particles, and soil inherits physical and chemical properties from this parent material. Bedrock sits underneath the weathered parent material and is made up of solid rock. This solid rock will stay hidden and undisturbed until an earthquake or erosion expose it to the surface where some of it will be weathered to make way for the next batch of parent material, which starts the soil forming process all over again. However, soil is not the end product of weathering rock, it is simply a stage in the mineral cycle, and the process by which nutrients such as carbon, nitrogen, and calcium cycle between living things, and the atmosphere and soils.

What is soil structure?

The form that the soil takes based on its physical and chemical properties is termed soil structure. Mineral particles that make up soil ranges in size from fine to coarse and are categorised accordingly as clay, silt, and sand. The amount of clay and organic matter in a soil plays an important role in determining soil structure. Clays carry a negative electric charge and can attract positively charged cations and water molecules, forming small aggregates. Sand and silt do not have any charge, but are combined into these aggregates when their surfaces become coated with clay or organic matter. These small aggregates can then form larger aggregates with the help of fungal hyphae. The structure of the soil depends on the size, shape and arrangement of these aggregates, and on the pores between these aggregates.

Why is structure important in your garden?

A ‘well structured’ soil will hold large amounts of water and dissolved nutrients. The aggregates will withstand cultivation and will not ‘puddle’ when wet or become dusty or set hard when dry. The network of pores will ensure adequate drainage and aeration, which are essential for the health of plant roots. Additionally, good structure will provide an excellent medium from which seedlings can emerge and through which roots can explore for moisture and nutrients.

Grading soil structure in your garden

Structureless soil No aggregates have formed and the soil consists of either individual separate grains, as in a sand, or a densely packed mass of particles without many pore spaces
Weakly developed soil structure Poorly formed aggregates that are hard to distinguish from the rest of the soil
Moderately developed soil structure Mainly well formed aggregates that, when disturbed, will break down to whole and broken aggregates and only a little unaggregated soil
Strongly developed soil Almost all of the soil particles are in clearly identifiable aggregates

How to improve soil structure?

The most preferred soil structure for growing crops contains a ratio of 2:2:1 of sand, silt and clay, and is referred to as loam or balanced soil. However, a good soil structure can be obtained by adding organic matter to the soil.

Clay and hardpan type soils can be improved by adding gypsum to the soil. Gypsum tends to improve soil structure by loosening the soil, improving drainage and aeration and reducing crusting. However, you still must add organic material to the soil to add nutrients and assist good soil structure.

Note: Gypsum use on sandy soils can aggressively leach out nutrients.

Functions of organic matter

Serves as a source of plant nutrients (especially nitrogen and phosphorus)
Helps the formation of soil aggregates with the help of microorganisms (especially fungi), improving soil structure, aeration and water infiltration and resisting erosion
Increases buffering of soils
Provides sources of energy that affect the activities of both macro and microfaunal organisms
Improves nutrient holding capacity (cation exchange capacity)
Improves soil colour
From: www.uvm.edu

Bugs

The soil is alive! The earth beneath our feet is filled with an amazing frontier of bizarre minuscule creatures of varied biology. While some people may find it hard to believe, our lives actually depend on these minuscule creatures living in the soil.

Some of the most important soil organisms include fungi, bacteria, protozoa, nematodes and arthropods. Individual species do not directly contribute to general soil health, it is rather the interactions between the many species that are important.

Who lives underground?

Bacteria Importance to soil
Bacteria on root hair

Nitrogen fixation
Bacteria are the only organisms on earth that can fix atmospheric nitrogen into ammonia, the form of nitrogen that plants can absorb. These bacteria are often integrated into the plant tissues (e.g. roots) of legumes (e.g. clover, beans), and form symbiotic relationships in which both parties mutually benefit, i.e. plants get nitrogen produced by the bacteria and the bacteria gets a place to live and food (carbon) produced by the plant through photosynthesis.

Bacteria are tiny (can only be seen under light (x1000) or electronic microscopes) single- celled life forms.·
2. Cyanobacteria (photosynthetic bacteria) secrete a polysaccharide that binds and holds soil particles together.
Their numbers can exceed 1 thousand billion per gram of soil with over 20 000 different species.
3. The carbon cycle
Bacteria and fungi help produce carbon dioxide (CO2) from dead organisms so that plants can use it for photosynthesis.
The organelles that make energy for your body (i.e. mitochondria) and the site of photosynthesis on green plants (i.e. chloroplast) were originally free-living bacterial cells.
4. Nutrient cycle
Bacteria decompose dead organisms, freeing nutrient components that are trapped to make them available for other organisms.
There are more bacterial cells on a human body than body cells.
5. Bioremediation
Bacteria help clean up our wrong doings, such as oil spills, pesticides, and other toxic materials, by returning them to their natural state in the environment while adding much needed fertility to the polluted environment.
Actinomycetes

A special group of bacteria that forms branched thread like filaments and gives soil its distinctive scent.

The above graphics are by permission of Saskatchewan Interactive.http://www.usq.edu.au

Fungi Importance to soil
Plant root covered with fungal hyphae

http://www.anselm.edu

  1. They decompose dead leaves and wood that cannot be broken down by bacteria.
    The fungal lineage includes common mushrooms, rusts, smuts, puffballs, truffles, morels, moulds, and yeasts.
  2. Fungi, both free-living and as a part of lichens (symbiotically associated fungi with algae or cyanobacteria, fungus and algae), contribute to soil stability by binding soil particles with hyphae (fungal cells).
    They provide numerous drugs (e.g. penicillin), foods like mushrooms (i.e. fruiting bodies, which are reproductive structures that produce spores), anti-rejection drugs (e.g. cyclosporine) used for organ transplants, and air bubbles in bread, champagne, and beer.
  3. Mycorrhizal fungi improve the host plant’s efficiency at obtaining nutrients and water while increasing the surface area associated with the plant root fungus, allowing the plant root more reach to explore the ground for nutrients and water.
    Some fungi (i.e. mycorrhizal fungi) develop a symbiotic relationship with most plant roots except brassicas. Some plants can’t survive to maturity without the fungi and are referred to as mycorrhizal-obligates.

Arthropods Importance to soil
The male, large garden cobweb spider (Eriophora pustulosa)

www.usq.au/spider

  1. Help aerate soil by mixing the soil.
    Includes members of the phylum Arthropoda (presence of an exoskeleton and jointed legs), such as beetles, spiders, mites, millipedes and other invertebrates (no backbone).
  2. Improve soil structure through their activities (consumption, digestion and excretion).
    1. Shred larger plant debris and mix it with soil microbes, assisting decomposition.
    2. Help spread beneficial microbes, control disease-causing organisms and regulate organism numbers by preying on them.
      Protozoa Importance to soil

www.marietta.edu

  1. Keeps bacterial communities growing by consuming vast numbers·
    A group of microscopic animal-like, single-celled creatures that are present in large numbers near plant roots due to the abundance of food (i.e. bacteria and organic matter).
  2. Provides nutrients to plant roots and stimulates the rate of decomposition through increasing bacterial activity, by excreting digested wastes.
    Some protozoas tend to live inside the guts of other creatures, e.g. the protozoa Trichonympha lives inside the termite gut and helps break down wood (cellulose) from its food but the actual digestion of wood is done by the bacteria living inside the gut.

Fruit

Pipfruit

Pipfruit is the name given to the fruiting trees that include apple, European pear, Asian pear, quince, and medlar.

Apples and pears were amongst the first fruit trees brought into New Zealand by colonising Europeans in the early 1840s.

Apples have in fact been grown in home gardens for centuries although the fruit have changed considerably in both appearance and flavour over time as new varieties (cultivars) have been selected.

Suggested varieties for the home garden

The more tried and true varieties are more commonly available in garden centres, but before choosing it is advisable to talk to your neighbours and garden centre about which varieties grow well in your area.

Apple Country of origin
Year

Description
Cox's Orange Pippin

UK

1830

Early season apple, distinctive flavour, highly rated in UK

Gravenstein

Germany

1832

Early, sweet apple, grown mainly in the North Island

Gala, Royal Gala

New Zealand

1960

Early to mid-season, sweet apple with crisp texture and striped skin, popular

Golden Delicious

USA

1890

Old favourite, a sweet eating apple, mid-season, being replaced by others that store longer

Delicious,

Red Delicious

USA

1881

Mid-season standard and easy to grow,

fruit can be stored

Splendour

sss sss
Late mid-season, good quality with crisp texture but surface is prone to bruising, no longer grown commercially

Braeburn

New Zealand

1952

Late, firm-textured variety, flavour improves after storage

Sturmer Pippin

UK

1843

Late, used for eating or cooking, acidic, easy to grow in the south

Granny Smith

Australia

1860

Late eating and cooking apple, versatile variety but may not ripen in the south

Pears

William's Bon Chretien

UK

1770

Early pear, popular for bottling

Packham's Triumph

Australia

1896

Popular for bottling

Winter Cole

Australia

1919

Late pear, can be stored

Winter Nelis

Belgium

Early 1800s

Late, good flavoured pear that can be stored

Doyenne du Comice

France

1849

Good flavoured pear, responds well to organic production

Pest and disease management

The biggest challenges facing growers of apples and pears in the New Zealand home garden lie in dealing with pest and diseases. Scientific studies allow us to understand the life cycles of these various pests in relation to the crop, and this knowledge allows us to identify the most appropriate methods to reduce the impact of these pests and diseases.

Codling moth (Cydia pomonella )

The larvae (caterpillar) of codling moth directly attack fruit, usually by tunnelling into the side of the fruit, where they feed on the fruit flesh and pips, before exiting, often through the calyx. The entry hole is often surrounded by a red halo of fruit skin and is characterised by the presence of frass (faecal pellets).

Cultural control methods
Removal of vegetation from the orchard understorey during the winter, through cultivation or mulching.
Use a wire brush to remove this loose bark during winter can reduce numbers of over-wintering codling moth caterpillars and pupae.
However, the success of such an approach is dependent on how close the nearest unmanaged codling moth-infested tree is because during spring, female moths may simply fly over the fence from another infested tree and lay eggs on your well-managed tree!

Codling moth traps
Catches of male moths in coddling moth traps can indicate the best time to apply an insecticide. When catches of moths total 10 or more in a trap, this is the best time to apply an insecticide.One or two well-timed insecticide applications offer the home gardener the most effective method of producing codling-free fruit.

Leafroller caterpillars
The lightbrown apple moth ( Epiphyas postvittana ) is the most common. Their pest status on apples and pears is due to surface feeding damage on fruit. As this damage is largely cosmetic, it is best for home gardeners to simply accept this damage. The alternative is monthly applications of insecticides throughout the growing season.

Scale insects
These are small sap-sucking insects that are covered with a hard shell. Scale insects become a problem mainly due to the sugary `honey dew' they excrete, which in turn provides a food source for the black sooty mould fungus.

Control of scale is relatively easily achieved by spraying with mineral oil (at the 2% rate) in the early spring, just as the buds begin to break and the first green tips are visible.

Sprays
The growing of fruit of sufficient quality and quantity to satisfy the home gardener can frequently be achieved without the use of sprays. Fruit quality can be considerably enhanced through pruning and hand thinning (as described above). If sprays are to be applied, attention should be given to achieving a thorough coverage of the entire tree, concentrating on the underside of leaves. A spreader/sticker should be added to all sprays, and the correct mixing rates used. If in doubt, garden centres can be contacted for advice.

Disease management:

Blackspot (Venturia inaequalis )
The blackspot fungus causes dark lesions on leaves and fruit of apples and pears. Home gardeners should remove all leaf material from the understorey below the trees, once leaf-fall is complete. This removes the over-wintering asco-spores of the fungus because it is these that release spores early spring and re-infect the foliage. Adding nitrogen under trees after leaf fall also aids leaf decomposition.

It is difficult to control blackspot using fungicides.

Studies have also demonstrated that blackspot prefers warm and wet conditions, so pipfruit gardens in locations like Auckland will suffer more from this disease than those in drier climates. Choosing a site for your pipfruit trees that dries out quickly after rainfall or watering can help reduce blackspot problems.

Powdery mildew (Podosphaera leucotricha )
This fungus disease affects apples only, and prefers conditions that are hot and dry. During the summer, infected shoot tips are coated with a white powdery substance, new growth aborts, and badly infected shoots shrivel and die. Management should focus on removal of infected shoots during winter and spring, with any infected prunings thoroughly disposed of. Fungicides can also be used to reduce powdery mildew, although this is not usually necessary in home gardens.

Unlike other fruits (e.g. citrus) the fertiliser requirements of pipfruit are not great, and care should be taken not to over-fertilise. Maintaining a weed-free growing area around establishing trees is important and can be achieved by mulching, applying herbicide, or hoeing.

Nutritional benefits of apples

There are so many reasons to eat an apple a day, they include:

Convienience – Apples are the perfect, portable snack. They are great tasting, energy-boosting, and free of fat.
Good and hearty – Research confirms that the antioxidants and phytonutrients found in apples help fight the damaging effects of LDL (bad) cholesterol, and are good for your heart. A Finnish study published in 1996 showed that people who eat a diet rich in flavonoids have a lower incidence of heart disease. Other studies indicate that flavonoids may help prevent strokes.
Aids digestion and weight loss – Just one apple provides as much dietary fibre as a serving of bran cereal. (That's about one-fifth of the recommended daily intake of fibre.) In addition to aiding digestion, dietary fibre promotes weight loss. A medium apple contains about five grams of fibre, more than most cereals. Also, apples contain almost zero fat and cholesterol, so they are a delicious snack and dessert food that's good for you.
Builds strong bones – Apples contain the essential trace element, boron, which has been shown to strengthen bones – a good defence against osteoporosis. It is a good idea to eat apples with their skin. Almost half of the vitamin C content is just underneath the skin. Eating the skin also increases insoluble fibre content. Most of an apple's fragrance cells are also concentrated in the skin. As skin cells ripen they develop more aroma and flavour.

Stone fruit (summerfruit)

Stone fruits have been valued for their fruit for many years. Apricot and peaches originated from China and spread through old trade routes 3–4000 years ago. Nectarines are more recent (at least 2000 years).

Cherries and European plums originated in Europe and the Japanese plum originated in China.

Site selection
Stone fruits do well in areas with cold winters and hot dry summers. Peaches, nectarines and some Japanese plums grow well at sea level, but apricots, European plums and sweet cherries tend to produce light crops and excessive vegetative growth in climates where there is inadequate winter chilling.

Most stone fruit require naturally fertile, free-draining soils.

Diseases
It is important to select varieties with good resistance to diseases. It is also important to search out any local knowledge on disease resistance.

Bacterial blast
causes limb and sometimes tree death
Trees exposed to cold in autumn and early spring can develop cankers under the bark of the trunk or branches. Cankers are usually associated with the production of amber-coloured gum that contains bacteria and oozes on to the outer bark. Unfortunately there are few control methods for bacteria apart from copper sprays. A programme based on copper has proved to be very effective over the years.

Bacterial spot
causes black spots on fruit and cracking of bark
Develops quickly under warm wet conditions from November onwards. Copper sprays have been used to help control bacteria in November/December.

Brown rot
causes major fruit losses at harvest both
on the tree and postharvest
This is the most important and limiting of the stone fruit diseases. A combination of warm and wet conditions at these times can cause high fruit losses with the fruit collapsing within a few days. Modern fungicides are remarkably effective against this disease. Sulfur can be used on most stone fruit (except apricots) but will not be adequate in a high risk year.

Peach leaf curl
causes reddening and distortion of leaves
of peaches and nectarines
Can severely debilitate trees if uncontrolled over several years. The most common treatment for leaf curl is copper, but ziram, thiram or dithianon can also be used.

Silver leaf
causes silvering of leaves and tree decline

All stone fruit are susceptible to the fungus, Chondrostereum purpureum, which causes silver leaf and tree decline.

PESTS

Pests of stone fruit (summerfruit)

Pest Apricot Peach Nectarine Cherry Plum
Aphids * * * *
Leafrollers * * * * *
Thrips * * * * *
Mites * * * * *
Cherry slug * *
Earwig * * *
Scales * * * *
Bronze beetle * * * * *
Grassgrub * *
More information on the pests of stone fruit can be found in the stone fruit 'more info' section.

Strawberries in your garden

The strawberry is a member of the rose family and belongs to the genus Fragaria derived from the Latin, fragare, meaning pleasant aroma. Strawberries originated from six main species, mostly from Europe, North America and Chile.

Strawberries are the most popular berry grown in the world. They are cultivated in most places in the world and world production is estimated at 2.8 million tonnes.

Strawberries for health

Strawberries are primarily eaten for their taste, but they do confer positive health benefits. Strawberries contain very high levels of a compound called ellagic acid, especially in the seeds and leaves, but the compound is also present in useful amounts in the fruit. Ellagic acid has a wide range of biological activity including anti-carcinogenic and anti-mutagenic properties.

Strawberries are also high in Vitamin C, Vitamin K and fibre and contain useful amounts of Vitamins B1, B5 and B6, and potassium, folate, manganese, magnesium, iodine, biotin (a B group vitamin) and tryptophan (an essential amino acid for human nutrition).

Red-fleshed strawberries are also moderately high in anthocyanins. Anthocyanins are powerful antioxidants that are beneficial in protecting against a range of cancers and heart disease.

Growing strawberries in the home garden

In the home garden, strawberries can be grown in containers, in hydroponic systems, or like the commercial growers do, in soil. Do not grow strawberries following solanaceous crops such as potatoes or tomatoes as these crops encourage the build-up of root diseases such as Verticillium sp. to which strawberries are very sensitive.

Fruit coming into contact with soil will rot. Straw is commonly used but any material such as plastic, newspaper or clean bark can be used.

Strawberries are rich in nutrients and these originate from elements in the soil. Feeding the soil with the nutrients removed by the plants while growing and fruiting is a key component in sustainable production systems.

Remove runners from the parent plants as these compete with fruit production.

Variety selection

Choose a variety known for its suitability for the area and resistance to pest and disease attack. For some areas, this may not be well known, but neighbours or garden centre staff may be able to suggest suitable varieties.

Pests and diseases of strawberries

Insect pests

Sucking insects (aphids, thrips and leafhoppers)

Control options:

  1. Do nothing. This encourages ladybirds, lacewings and other natural controls.

Chemical controls. Use chemicals that are:

safe to the applicator
not persistent in the environment
control the pest target but have minimal effect on other species
3. Management controls. Start with clean plants so insects are less likely to be carrying diseases.

Root feeding insects

Grass grub can be a major problem with strawberries. Management control is desirable, e.g., controlling the pest by encouraging birds and rolling at its source usually surrounding lawns.

Mites
Buying high health plants and not using chemicals that can affect natural predators are the best control options.

Slugs and snails
Drowning in beer, or using baits that are harmless to hedgehogs and other predators are effective controls.

Fungal diseases

Botrytis

The disease carries over on old leaves, so starting with clean planting material and removing any dead and dying leaves and rotten fruit throughout the season is a key part of managing botrytis.

Mycosphaerella leaf spot (frog’s eye)

High infection levels result in smaller fruit with less flavour. Encouraging air movement around the plants will help prevent germination as this disease also needs high humidity.

Anthracnose

Can cause black spots on leaves and leaf stems and occasionally crown rot, but the main problem is black fruit rot. Removing old plants before planting new ones should ensure that the disease does not spread from these.

Spray timing

Unnecessary spraying leads to resistance build-up and possible residue problems. Decisions about the need to spray should be based on what is happening in the strawberry plants, rather than what is written in a book, or what was done last year.

Feijoa

The feijoa (Acca sellowiana) is a member of the Myrtaceae family and is native to southern Brazil and Uruguay. Feijoas were introduced to Europe in 1890 by French botanist Edouard André and have since become a common tree in many countries, although the modern feijoa cultivars are distant cousins of the original specimen introduced by André (Table 1).

Table 1: Feijoa cultivars and their attributes.

Fruit size Sensory attributes Harvest season/storage
Unique medium-large soft & juicy flesh, mildly aromatic very early season, does not require cross-pollination
Gemini medium strong acid flavour early season, good storage life
Pounamu medium good flavour early season, good storage life
Apollo very large
( > 260 g) sweet with excellent flavour mid season, delicate, good storage life
Kakapo medium good flavour mid season
Opal Star medium-large excellent smooth flesh mild flavour late season,good storage qualities
Wiki Tu large-very large sweet with good flavour late season
Triumph medium good flavour late season

Site selection

The feijoa tree is hardy and will grow almost anywhere in New Zealand. However, late-maturing cultivars may not be suitable for cooler regions because early winter frost can damage fruit before they ripen.

Cultivar selection

Most cultivars require cross-pollination to produce good quality fruit. Lack of cross-pollination can result in small fruit or hollow fruit with little or no pulp development. Planting a self-fertile cultivar such as Unique, which has self-fertile flowers (see Table 1, above), is an option for the home gardener.

Flowering

Flowering begins around November and continues for four to six weeks. Feijoas are pollinated by birds that feed on the sweet and juicy petals of the brightly coloured flowers. In New Zealand, the most important bird species for pollinating feijoa flowers are blackbirds (Turdus merula) and mynas (Acridotheres tristis). Invertebrates and small birds visit feijoa flowers but are ineffective pollinators.

Tree management

Prune to provide access for birds so that they can move freely amongst the branches during flowering and to allow easier fruit harvesting.

Fruit harvest

Fruits are ready to harvest in March to June. Feijoa fruit attain optimum harvest maturity just prior to the time of natural fruit drop. Most home gardeners usually collect mature fruit from the ground, but fruits are likely to be healthier (i.e. last longer) if they are `touch-picked’. This involves gently tilting the fruit sideways or forward, gently pulling them down and harvesting them only if the fruit gives way easily. Research has shown that bruising will make fruit more susceptible to fungal rots. Therefore, fruits picked up from the ground may not last as long.

Pests and diseases

A number of pests and diseases are present on feijoa but most are unlikely to cause serious damage or affect yields. However, a recent arrival, the Australian guava moth, is causing commercial growers some concern. Scientific research may provide some answers in the future.

Australian guava moth

This moth is present in Northland, the area north of and including the greater Whangarei region. Guava moth lay their eggs (Fig. 1) at the stem and style end and in cracks and crevices on fruit. The resulting larva (Fig. 2) feed inside the fruits, causing premature fruit drop. Pupation occurs in loose soil and debris on the ground. Guava moth damage may affect the productivity of a garden feijoa tree and the gardener may notice a hole in the fruit with frass (insect feces) at the entrance (Fig. 3). Guava moth infestation is obvious once the fruit is opened as the flesh is brown and rotting. Pheromone traps to catch adult guava moths (Fig. 4) are available from your local Fruit-Fed supplier.

(pic)

Figure 1: Guava moth eggs in a crack on a fruit surface.

(pic)

Figure 2: Guava moth larva.

(pic)

Figure 3: Guava moth larva feeding on a macadamia with insect frass at the entrance to the hole.

(pic)

Figure 4: An adult guava moth.

Tamarillos

History
Interesting fact
Nutritional benefits
Recipe
Site selection
Pruning
Major pests and diseases

The tamarillo (Cyphomnadra betecea (Cav.) Sendt) is a member of the Solanaceae family along with the potato, tomato, eggplant, and capsicum pepper.

History

The tamarillo was first introduced to New Zealand from Asia in the late 1800s. Only yellow and ‘purple’ fruited strains were produced from the original introductions, but the red type was developed by an Auckland nursery during the 1920s from seed sourced from South America. Other red strains, developed independently, appeared soon afterwards. Since then, continued reselection of these original red strains by growers has led to the large high-quality varieties that are available today.

Interesting fact

In the early days, tamarillos were referred to as tree tomatoes. However, on 31 January 1967, after almost unanimous agreement amongst growers and with the consent of what was then the New Zealand Department of Agriculture, the fruit’s commercial name was officially changed from tree tomato to tamarillo.

Nutritional benefits

The tamarillo is an extremely nutritious fruit, containing good quantities of several important vitamins – A, B6, C and E – and is rich in iron and potassium. The fruit is low in sodium. An average tamarillo contains less than 40 calories.

Recipe for Tamarillo Muffins

Ingredients
½ cup sugar
2 cups flour
2½ teaspoons baking powder
2 teaspoons mixed spice
1 egg, lightly beaten
½ cup milk
100 g butter, melted
1 cup (approx 3) peeled and chopped tamarillos
1 extra tamarillo, peeled and thinly sliced
Method
Preheat the oven to 200°C. Lightly grease 8-10 muffin pans.
Place the sugar and sifted flour, baking powder and mixed spice in a bowl. Combine the egg, milk and melted butter.
Add the liquid ingredients and chopped tamarillos to the dry ingredients and combine quickly, until just moistened.
Spoon the mixture into muffin pans until almost full. Top with a thin slice of the extra tamarillo. Bake for 20-25 minutes depending on the size of the muffins. Makes 8-10
© Jan Bilton

Site selection

The tamarillo is a subtropical shrub and is extremely frost intolerant so its growth is restricted to areas where frosts are infrequent and only slight.

The plant prefers a light, well-drained soil. It is highly intolerant of excess soil moisture and rapidly succumbs when the soil is waterlogged. On the other hand, its large soft leaves and shallow rooting system causes it to react unfavourably to drought conditions – it needs ample moisture during summer.

Pruning

Pruning period

Pruning can commence in early spring (August onwards) once the danger of frosts has passed and the majority of the previous crop has been harvested. This will vary from district to district, and from site to site within a district. It may continue through November and even into December. However, most blocks are pruned by the end of October.

Importance of pruning

Tamarillos produce their fruit on the current season’s growth. If trees are left unpruned, the new fruiting wood gradually extends from the ends of the branches and the laterals, leaving the centre of the tree more or less barren. Frequently the weight of the fruit produced on the ends of long, weak, spindly branches or laterals causes them to break.
Pruning in early spring or not pruning at all normally results in early maturity. Pruning that is delayed until November results in a later crop because of the enforced delay in spring shoot growth upon which new flowers will be born.
Light pruning (up to half of the old canopy) produces weak regrowth that branches and sets flowers quickly, resulting in a heavy, early maturing crop of small to medium sized fruit.
In contrast, hard pruning (back to near the original forks of the tree) results in vigorous regrowth. The crop from these is usually smaller in quantity but larger in fruit size, maturing a little later than lightly pruned tress of the same time.
Pruning, whether hard or light, is therefore recommended.

Major pests and diseases

Some of the major diseases of tamarillos include the tamarillo mosaic virus, powdery mildew, and sooty mould. The major pests are whitefly, aphids and green vegetable bug.

Aphids
One of the major pests of tamarillos is the aphid. Six species of aphid are known to attack tamarillos, but by far the most important of them is the green peach aphid (Myzus persicae).

It is most important to control aphids as they carry and transmit viruses in tamarillos. Aphids may be present on tamarillos for the whole year but are present in greater numbers from spring to autumn. Peak flights are in early spring, late summer and autumn. Although not particularly deleterious to plant growth, the main concern with their presence is the transmission of viruses such as Tamarillo mosaic virus (TaMV).

Ladybirds feed on this pest, so practices that encourage the presence and activity of ladybirds will prove beneficial.

Tamarillo mosaic virus (TaMV)
The disease symptoms of TaMV are a dark pale mosaic mottling on the leaf and fruit skin as well as unsightly irregular blotches that are a darker red than the normal skin colour. No symptoms appear inside the fruit and eating quality is not affected. On golden tamarillos, the darker red blotch is most unsightly because of the paler background colour typical of this class of fruit.

Once symptoms appear, the only control for TaMV is to remove severely infected trees.

Ornamental

Turf

Introduction to lawn and turf

In recent years there has been a significant move away from the use of fine grass species such as browntop (Agrostis capillaris) and fine fescue (Festuca rubra) in favour of turf-type perennial ryegrass (Lolium perenne) for lawns and turf. An important contributing factor to this move has been the dramatic improvement in the quality of turf-type perennial ryegrass cultivars. The rapid germination and quick establishment of perennial ryegrass, even in cold conditions, make it easier and more reliable for homeowners and contractors to establish. The newly sown lawn can often be used within as little as four to six weeks.

Development of turf ryegrass

The first turf-type perennial ryegrass cultivar was bred 25 years ago in the USA. At that time the New Zealand Government was concerned that wholesale importation of dwarf turf cultivars could result in the contamination of our own pasture seed industry so they introduced an ‘acceptable cultivar list’. Only cultivars that were tested and found to have merit were allowed into the country. After careful assessment, it was realised that different cultivars could be kept from cross pollinating if normal isolation practices were followed. Now turf ryegrass seed is an important crop in New Zealand.

Interesting fact: The first use of a turf ryegrass as a sports turf in New Zealand was in the late 1970s when the cultivar Manhattan was imported from the USA and sown into the Basin Reserve cricket pitch.

Special features of turf ryegrass

Versatile and can be grown anywhere if it is sown heavily and kept frequently mown. For example, it can be mown at 5 mm in tennis courts and at 12-15 mm in a home lawn.
Fine, dense, and compact growth.
Mows cleanly, and produces dense turf.
Tends to produce seed heads over a short period, but vegetative growth resumes once these are mown off.
Not affected by autumn Fusarium patch disease, which severely affects browntop turf.
Note: Pasture ryegrass is much coarser than turf ryegrass.

The discovery of endophytes in ryegrass

Turf ryegrass did not gain immediate acceptance in New Zealand because it could disappear completely in drier regions over a single summer while in other areas it appeared to perform well.

In the 1980s New Zealand scientists, along with international collaborators, found that surviving grasses contained a fungus that grew within the plant. The fungus was consequently called an endophyte (pronounced “end - oh – fight’) with the generic name of Neotyphodium species. The association between the plant and fungus is synergistic, as both organisms benefit. The endophyte makes the grasses resistant to attack from insect pests, including Argentine stem weevil (Listronotus bonariensis) and black beetle (Heteronychus arator), improving the survival rates of the grasses. The resistance is due to the release of a number of different alkaloids, including peramine, that deter insect feeding. Plants infected with the endophyte do not have disease symptoms. The fungus cannot be passed on to non-infected turf. Instead, the turf can be given resistance to Argentine stem weevil by over sowing endophyte-infected cultivars that replace the susceptible cultivars over time.

Within a year of these discoveries, New Zealand turf grass breeders in Canterbury found that almost all of the turf cultivars bred overseas lacked endophyte. Nowadays, nearly all turf ryegrass cultures contain endophyte.

Benefits of endophyte in turf ryegrass

Turf cultivars with high endophyte content have increased growth and vigor, making them more tolerant to drought stress, summer weed invasion, and other possible turf diseases. Endophyte affects more than 40 invertebrate pests, mostly insects that feed on the lower part of the tiller rather than root feeders such as grass grub (Costelytra zealandica). Future research is likely to lead to endophyte strains for turf that will provide resistance to an even wider range of insect pests.

Seed quality

Buyers of perennial ryegrass seed are warned that much of the seed sold to homeowners is of indifferent quality. Furthermore, seed that is stored for 18 - 24 months under normal storage conditions will lose its endophyte. Buyers must ensure they purchase good quality seed by looking for the following:

  1. is it a named turf cultivar that has been bred in the last 10 years?
  2. is it a cultivar with a high endophyte content?
  3. is the seed less than 18-24 months old?
  4. does the seed have a high germination rating, as determined by a recent germination test?
  5. is the seed pure, as indicated by a purity and germination certificate?

Adaptation and management of perennial ryegrass

Not well adapted to sandy or gravely soils. It is best adapted to medium textured silt loam soils and clays, unless well irrigated.
Prefers a neutral soil (pH 5.5-6.5) and good availability of phosphorus and potassium.
Regular nitrogen fertilisation is needed to maintain good colour and active growth.
Grows faster than fine grass so it needs more regular mowing, like browntop or fescue.
Looks attractive when mowed with either a reel or rotary mower, but a reel mower gives the best quality cut.

Routine care of grass lawns and turf

Management of turf ryegrass

Perennial ryegrass is best adapted to medium-textured, silt loam soils and clays. It survives summer drought best on heavy soils but is often killed on light sandy or gravely soils.

Maintaining a desired height

Regular cutting of the grass with a tondeuse thermique encourages tillering of the plant to create a dense, healthy sward with an even, attractive finish.

Cutting height and frequency

For the first cut of a new lawn, cut the grass when it reaches 5 cm, to a height of 2.5 cm, and gradually lower the cutting height in subsequent mowings until the desired height is reached.

For high-quality lawns, cut the turf to 1.5 cm as needed throughout the year. For utility lawns, cut the turf to a height of 4 cm as needed in winter, and to 2-3 cm on a weekly basis during spring and autumn.

Rule: Mow when the grass has grown by 50%, so you don’t have to cut off more than one-third of the blade.

Lawn clippings and mulching

If the lawn is less than 70 mm in height, grass clippings can be left on the lawn after cutting, rather than removing them with a catcher. The clippings decompose quickly, returning nutrients to the soil within two weeks after mowing. The amount of nitrogen returned to the soil is as much as 88 kg/ha. Since nitrogen is the most expensive component of all lawn fertilisers, it pays to leave clippings.

Clippings also enhance the habitat for beneficial microorganisms and earthworms.

Fertiliser

Regular applications of fertiliser ensure a vigorous healthy lawn. Most of the nutrients essential for growth are plentiful within the soil, except for nitrogen (N), phosphorus (P), potassium (K) and iron (Fe). Nitrogen-deficient grass is yellow-green, and lacks vigour.

Nitrogen produces deep green leaves, rapidly growing leaves and shorter roots. Phosphorus facilitates metabolic functions plus energy storage and use. Potassium is used to create cell components, and it helps regulate respiration and transpiration. It helps the plant grow, withstand environmental stress and resist disease.

Two applications of fertiliser a year are sufficient. Apply in late spring and early autumn. Nitrogen applied in summer may stimulate lush growth and encourage diseases.

Thatch can be a problem on a lawn that is intensely fertilised and watered or on a lawn that receives infrequent cutting. Pesticide use is also implicated.

Watering

Established turf generally withstands dry periods, but growth is retarded. Under drought stress, turfgrasses dry up and the leaves roll and turn a dull purplish colour, a process called dry wilt. However, too much water may induce wet wilt, which occurs when the soils become saturated, and the movement of oxygen into the soil and carbon dioxide out of the soil ceases.

Water any turf just before it begins to wilt. This stage can be recognised because the grasses develop a dull purple cast, and the leaf blades begin to roll or fold. Further, the grass does not spring back after the lawn has been walked on.

Preferably, water early in the morning when conditions are calm and temperatures are low, so less water is lost to evaporation. Watering in late evening has the additional benefit of reducing water loss to evaporation, but because the grass usually stays wet all night, watering at this time can induce disease outbreaks.

How much?

Water to a depth of 10-15 cm. Deep watering encourages development of an extensive root system, enabling the plants to utilise nutrients and water in the soil more efficiently than shallow root systems.

General guide: Turf needs about 21 mm of water once a week during summer, with a supplementary irrigation at noon during hot days.

Turf aeration

Aeration of the soil allows deep root growth, enhances establishment, and reduces soil compaction and excessive thatch. Methods of aeration include scarifying, slitting, hollow tining (coring) and spiking. Aerate during spring and autumn. Dry summer conditions make the turf more susceptible to drought.

Scarifying – Scarifying removes thatch, permitting air to enter the lawn surface and enhancing thatch degradation by micro-organisms. Rake the lawn with a wire or spring-tined rake, or a powered scarifier, in two directions, one at right angles to the other. Moss should be killed prior to scarifying to prevent it spreading to other parts of the lawn during scarification.
Slitting – A slitting machine comprises flat knife-like blades that cut slits through the thatch to a depth of 8-10 cm, allowing air into the soil.
Hollow tining – A mechanical or hand tiner removes cores of grass, thatch and soil, making a series of holes across the lawn about 10 cm apart. The cores need to be filled with a sandy top-dressing to prevent them from closing.
Spiking – Achieved by using a mechanical or hand spiker or roller aerator, or a garden fork. Angle the spikes back slight to raise the turf gently, to encourage deep root growth by creating fissures in the soil.

Laying down a new lawn

Establishing a new lawn that is lush, healthy and largely weed free is a challenge for any gardener. However, if the right steps and advice are followed, the end result of producing a new lawn that is easy to maintain and looks great is well worth the time and effort.

Preparing the soil
A thorough job of preparing the soil is critical to achieving the perfect lawn. This includes eradicating weeds, drainage, soil pH levels, levelling, firming/raking, watering and fertilising.

Eradicating weeds
Kill existing turf to eliminate unwanted lawn grasses and perennial weeds, particularly weeds that have rhizomes or deep tap roots, as they regenerate rapidly from small pieces of root. Examples are dandelion (Taraxacum officinale), nut grass (Cyperus rotundus), docks (Rumex spp.), soursob (Oxalis pes-caprae) and other Oxalis spp.

Control method
Initially, apply a broad-spectrum non-residue herbicide such as glyphosate or essential oils in an ‘organic interceptor’ to eliminate grass weeds and some broadleaf annual weeds. Plants that survive the first herbicide application should be eliminated using a selective herbicide.

Drainage
Drainage is only required on heavy clay soils and can be improved by incorporating two parts sand to one part soil. However, a drainage system of pipes laid in a trench, backfilled with gravel is a better alternative. For most loam soils that receive 600-1000 mm rainfall, one drainpipe every 5-8 m is recommended. Heavier clay soils or sites in areas with rainfall above 1000 mm will require drainpipes laid at closer intervals.

Soil pH
Grasses grow satisfactorily at pH levels of 5.5-7.0. In this pH range, nutrients required by turf grasses are soluble rather than being bound up in the soil. Soil pH can be tested using a kit available from garden centres. For acidic soils (pH less than 5), dig or rotavate lime (calcium carbonate) into the soil. The recommended rate depends on the starting pH and soil type (Table 1).

Table 1: Amount of lime (g/m²) required for different soils.

Starting pH Sandy Loam Clay
4.5 190 285 400
5.0 155 235 330
5.5 130 190 260

Levelling the site
First level the site by eye. More accurate levelling can be achieved by running builder’s string on pegs inserted into the ground.

Firming and raking
Tread the soil evenly about three times to firm it. Rake the surface to provide a fine tilth. Remove stones more than 1 cm in diameter if the soil is being prepared for sowing, or 2.5 cm in diameter for turfing. Allow 3-4 weeks for weed seeds to germinate, and treat the area with glyphosate to kill them.

Watering
New turf requires watering at frequent intervals to keep the seed or turf moist during this initial 2-week growth period until the root systems develop. Treat the lawn as an established turf after 1 month.

Fertiliser
A few days before establishing the lawn, apply a compound granular fertiliser containing nitrogen (N), phosphate (P) and potassium (K) to the prepared soil surface at a rate of 150-200 g/m². Rake the fertiliser into the surface.

Establishing the lawn

Turfing
Turf can be applied any time of the year except during hot dry periods. Lay turf on to a moistened soil surface to encourage root development. Starting at the edge of the site, lay the first row of turf in a straight line. Standing on planks placed on the first row, rake over the soil on which the next row is to be laid. Lay the second row so that the turf forms an alternate bond, like bricks in a wall. Cut the edges to shape with a sharp flat or half-moon spade; use the inside of a hose for a curved edge or a plank for a straight edge. Roll the newly laid turf with a light roller (50 kg), and brush a top-dressing of sand and soil mix into the joins between the turf pieces to encourage the roots to spreads into the gaps. Water the turf thoroughly.

Sowing seed
Calculate the amount of seed required by multiplying the size of the area (m²) by the recommended sowing rate (g seed/m²). Shake the seed bag to mix the seeds.

If sowing by hand, divide the area into equal sized sections, e.g. 1 m x 1 m, to ensure an even distribution of seed cover. Measure the correct amount of seed (Table 2) for each section, and scatter half the amount in one direction and the remainder at right angles. Repeat for each section.

If sowing by machine seed spreader, divide the amount required for the lawn by half, and sow one half in one direction and the remainder at right angles to the direction of the first application.

Table 2: Seed sowing rates (g/m²)

Turfgrass species g/m²
Fescues & bents 23-30
Perennial ryegrass & other grasses 35-40
Bents (Agrostis spp.) 8-10
Carpet grass (Axonopus spp.) 8-12
Couch grass (Cynodon dactylon) 5-8
Centipede grass (Eremochloa ophiuroides) 1.5-2.5
Red fescue (Festuca rubra rubra) 15-25
Perennial ryegrass (Lolium perenne) 20-40
Kentucky bluegrass (Poa pratensis) 10-15
After sowing, lightly rake over the surface and water with a sprinkler. Sowing the grass seed at the proper depth (2-4mm) is very important because the food reserves of the seed (endosperm) may be used up before the new shoot can reach the soil surface and start making its own food through the process of photosynthesis. A biodegradable paper can be used to cover the newly sown seeds to prevent erosion on sloping lawns. The seeds will germinate 1-2 weeks after sowing.

Repairing lawn damage and annual maintenance for lawn care

Renovating neglected lawns

Lawn renovation involves a series of procedures to restore a lawn to good condition. In early spring, cut the turf to 5 cm and remove the clippings. Reduce the cutting height incrementally by subsequent mowing until the required height is reached. Then fertilise the lawn and apply herbicide (around two weeks later) to control weeds. Reseed bare or uneven patches 1-2 weeks after the herbicide application. At the beginning of autumn, aerate, top-dress with a sand-soil mix, and fertilise the lawn in that order. Then follow a regular maintenance programme (see Table1).

Damaged edges

Edges that have been damaged in small areas can be repaired by cutting the turf with an edger against a plank of wood (Figure 1). Then slice under the section of turf with a spade and slide the section towards the lawn edge until the damaged area is outside the lawn. Trim off the damaged part to align the turf with the existing lawn edge. Re-grass the resulting gap in the turf by adding a little soil and reseeding with a grass mixture. This method maintains the edge of the lawn without it slumping as would happen if the damaged area was simply removed and reseeded with a grass mixture.

Figure 1: Repairing a damaged edge.

Levelling a hump or hollow

Cut a cross through the turf in the affected area and peel back the cut turf (Figure 2). To level a hollow, fork over the soil beneath and fill in with topsoil, then firm the ground. For a hump, remove the excess soil until the ground is level, fold back the cut turf and tamp it down with the back of a rake before top-dressing and watering.

Figure 2: Levelling a hollow or hump.

Annual maintenance programme

Table 1: Summary of annual maintenance programme

Activity Spring Summer Autumn Winter
Early Late Early Late Early Late
Mowing Cut to 3 cm height Keep at 3-6 cm Keep at 3-6 cm Keep at 3-6 cm Keep at
3-6 cm Keep at 4-8 cm Keep at 4-8 cm height
Watering 21 mm/wk 21 mm/wk If necessary
Fertilising N/P/K N/P/K
Aerating & scarifying Lightly scarify Spike or slit areas subject to heavy wear Scarify & remove thatch Aerate
Moss control Lawn sand Lawn sand
Weed control Herbicide Herbicide
Worms
Insect pest & disease control Insecticide Insecticide & fungicide
Other procedures Roll to flatten frost heave Remove fallen leaves
Remove fallen leaves.
Service tools

Turf-type perennial ryegrass

for lawns and turf

In recent years there has been a significant move away from the use of fine grass species such as browntop (Agrostis capillaris) and fine fescue (Festuca rubra) in favour of turf-type perennial ryegrass (Lolium perenne) for lawns and turf. An important contributing factor to this move has been the dramatic improvement in the quality of turf-type perennial ryegrass cultivars. The rapid germination and quick establishment of perennial ryegrass, even in cold conditions, make it easier and more reliable for homeowners and contractors to establish. The newly sown lawn can often be used within as little as four to six weeks.

Development of turf ryegrass

The first turf-type perennial ryegrass cultivar was bred 25 years ago in the USA. At that time the New Zealand Government was concerned that wholesale importation of dwarf turf cultivars could result in the contamination of our own pasture seed industry so they introduced an ‘acceptable cultivar list’. Only cultivars that were tested and found to have merit were allowed into the country. After careful assessment, it was realised that different cultivars could be kept from cross pollinating if normal isolation practices were followed. Now turf ryegrass seed is an important crop in New Zealand.

Interesting fact: The first use of a turf ryegrass as a sports turf was in the late 1970s when the cultivar Manhattan was imported from the USA and sown into the Basin Reserve cricket pitch.

Special features of turf ryegrass

Versatile and can be grown anywhere if it is sown heavily and kept frequently mown. For example, it can be mown at 5 mm in tennis courts and at 12-15 mm in a home lawn.
Fine, dense, and compact growth.
Mows cleanly, and produces dense turf.
Tends to produce seed heads over a short period, but vegetative growth resumes once these are mown off.
Not affected by autumn Fusarium patch disease, which severely affects browntop turf.
Note: Pasture ryegrass is much coarser than turf ryegrass.

The discovery of endophytes in ryegrass

Turf ryegrass did not gain immediate acceptance in New Zealand because it could disappear completely in drier regions over a single summer while in other areas it appeared to perform well.

In the 1980s New Zealand scientists, along with international collaborators, found that surviving grasses contained a fungus that grew within the plant. The fungus was consequently called an endophyte (pronounced “end - oh – fight’) with the generic name of Neotyphodium species. The association between the plant and fungus is synergistic, as both organisms benefit. The endophyte makes the grasses resistant to attack from insect pests, including Argentine stem weevil (Listronotus bonariensis) and black beetle (Heteronychus arator), improving the survival rates of the grasses. The resistance is due to the release of a number of different alkaloids, including peramine, that deter insect feeding. Plants infected with the endophyte do not have disease symptoms. The fungus cannot be passed on to non-infected turf. Instead, the turf can be given resistance to Argentine stem weevil by over sowing endophyte-infected cultivars that replace the susceptible cultivars over time.

Within a year of these discoveries, New Zealand turf grass breeders in Canterbury found that almost all of the turf cultivars bred overseas lacked endophyte. Nowadays, nearly all turf ryegrass cultures contain endophyte.

Benefits of endophyte in turf ryegrass

Turf cultivars with high endophyte content have increased growth and vigor, making them more tolerant to drought stress, summer weed invasion, and other possible turf diseases. Endophyte affects more than 40 invertebrate pests, mostly insects that feed on the lower part of the tiller rather than root feeders such as grass grub (Costelytra zealandica). Future research is likely to lead to endophyte strains for turf that will provide resistance to an even wider range of insect pests.

Seed quality

Buyers of perennial ryegrass seed are warned that much of the seed sold to homeowners is of indifferent quality. Furthermore, seed that is stored for 18 - 24 months under normal storage conditions will lose its endophyte. Buyers must ensure they purchase good quality seed by looking for the following:

  1. is it a named turf cultivar that has been bred in the last 10 years?
  2. is it a cultivar with a high endophyte content?
  3. is the seed less than 18-24 months old?
  4. does the seed have a high germination rating, as determined by a recent germination test?
  5. is the seed pure, as indicated by a purity and germination certificate?

Adaptation and management of perennial ryegrass

Not well adapted to sandy or gravely soils. It is best adapted to medium textured silt loam soils and clays, unless well irrigated.
Prefers a neutral soil (pH 5.5-6.5) and good availability of phosphorus and potassium.
Regular nitrogen fertilisation is needed to maintain good colour and active growth.
Grows faster than fine grass so it needs more regular mowing, like browntop or fescue.
Looks attractive when mowed with either a reel or rotary mower, but a reel mower gives the best quality cut.

Weed and pest control

General

Various perennial weeds that can thrive in short regularly mown lawns can be troublesome. They usually originate from seeds carried by wind or birds. Once lawn weeds have germinated, mowing then rapidly spreads them. Thus, early treatment of the weeds is required to eliminate them from the lawn.

Some weeds, e.g. cape-weed (Arctotheca calendula) and daosoes (Bellis perennis), may look attractive in utility lawns, but are undesirable in high-quality lawns. In some regions they are declared as noxious weeds. Many weeds survive regular cutting, and so must be controlled with herbicides or by hand weeding.

The most troublesome lawn weeds are winter grass (Poa annua), nut grass (Cyperus rotundus), slender speedwell (Veronica filiformis), wax weed (Hydrocotyl americana) and baby’s tears (Soleirolia soleirolii). These persistent weeds are not controlled by herbicides registered for lawns. Moss may also be a problem.

Other lawn weeds that are less of a problem as they are controlled by herbicides include yarrow (Achillea millefolium), Mouse-ear chickweed (Cerastium glomeratum), bindii or Onehunga weed (Soliva pterosperma), broad-leaved plantain (Plantago major), self-heal (Prunella vulgaris), creeping buttercup (Ranunculus repens), Sheep’s sorrel (Rumex acetosella), lesser yellow trefoil or suckling clover (Trifolium dubium), and common white clover (Trifolium repens).

Good lawn care is an effective preventive measure. The presence of numerous weeds in a lawn usually indicates that the grass is not growing sufficient vigorously to prevent weeds from establishing. Low soil fertility and drought are the most common causes for poor growth of turfgrasses. Soil compaction and mowing the grass too short may also lead to invasion by moss.

Removing weeds

Hand weeding

Removing weeds by hand is effective for a few scattered rosetted weeds such as English daisy (Bellis perennis), dandelion (Taraxacum officinale), and plantains (Plantago spp.) Use a daisy grubber or hand fork to lift the weeds, and then firm back the displaced turf.

Moss

Moss is prevalent in lawns where soils are compacted, have poor drainage, low fertility, insufficient light, closely cropped cutting regimes, and too acidic or basic soils. Moss can be removed temporarily using a special herbicide containing benzalkonium chloride, copper sulfate or dichlorophen (Table 6), followed by scarification. Iron (ferrous) sulfate in lawn sands can also be used to eradicate moss.

However, unless the soil is in a condition conducive for healthy turf, the moss will return, necessitating removing the underlying cause of moss intrusion. Improving soil aeration, drainage and fertility, and top-dressing on light soils to assist in water retention, could improve lawn health. Adopting an annual maintenance programme (Table 4) will alleviate moss invasion.

Herbicides

The herbicides registered for use in turf and the weeds they control are listed in Table 1. They are selective for specific weeds, and usually do not harm the turf grasses when applied at recommended rates to lawns more than six months old. Higher rates may kill even a mature lawn. Younger turf may be susceptible to herbicides, even when they are applied at rates recommended on the label.

The herbicides translocate within affected plants from the leaves to the roots. Within a few days of application, the weeds usually begin to distort and shrivel.

Proprietary lawn herbicides often combine two or more active ingredients in order to control the widest possible range of weeds in one application. Active ingredients that are commonly mixed include 2,4-D, which is selective against broad-leaved rosetted weeds. Mecoprop kills small-leaved and creeping weeds such as clovers (Trifolium spp.) and yarrow (Achillea millefolium). Dicamba may be combined with 2,4-D or MCPA to widen the spectrum of control. Bromoxynil is usually combined with MCPA or dicamba to control Onehunga weed.

Application

Apply the selected herbicide to a lawn in spring, about two to three weeks after growth commences, when plant growth is vigorous. Then, weeds are more susceptible to the effects of the herbicide, and the grasses will rapidly colonise the spaces vacated by the dead weed plants.

Allow at least three days after mowing before applying the herbicide, to allow enough time for the weeds to develop new leaf surfaces to absorb the herbicidal compounds. Further, wait three days after herbicide application before mowing the lawn to allow time for the herbicide to translocate to the roots.

Lawn weeds differ in their susceptibility to herbicides. Dandelions and plantains can be killed after one to two applications. Clovers may require two to three applications at four to six-week intervals. Creeping speedwell (Veronica persica) may survive several applications.

Check label for instructions on disposal of lawn clippings. For some herbicides such as chlorpyralid, clippings should not be added to compost heaps that are used as mulch around sensitive plants, or disposed of at any garden waste recycling centre. In such a case, clippings should be mulched back into the lawn, or burnt.

Table 1: Herbicides registered for control of weeds in turf lawns.

Active ingredient Trade name Weeds controlled
methylarsinic acid AGPRO MSMA 600 Paspalum, summer grasses
bromoxynil, ioxynil, mecoprop Axall Allseed, buttercups, calandrinia, capeweed, chamomiles, chickweeds, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, dichondra, docks, dove’s foot, field pansy, henbit, mayweeds, Onehunga weed, oxtongue, parsley piert, plantains, portulaca, pratia, scarlet pimpernel, shepherd’s purse, speedwell, starweed, thistles, twin cress, willow weed, wireweed
2,4-D, dicamba Banvine Chamomiles, chickweeds, clovers, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, docks, dove’s foot, henbit, mallows, Onehunga weed, oxtongue, parsley piert, pennyroyal, plantains, scarlet pimpernel, shepherd’s purse, storksbill, thistles, twin cress, willow weed, wireweed, yarrow
bentazone Basagran Buttercups, calandrinia, chamomiles, chickweeds, cotula, mayweeds, Onehunga weed, parsley piert, plantains, scarlet pimpernel, shepherd’s purse, storksbill, willow weed
benzalkonium chloride, copper sulfate Mossoff Algae, lichen, liverworts, moss
dichlorophen Mostox Algae, lichen, liverworts, moss
benzalkonium chloride Yield Algae, lichen, liverworts, moss
chlopyralid Tango, Versatill, Void Chamomiles, clovers, cudweed, daisy, dandelion group, docks, mayweeds, Onehunga weed, oxtongue, thistles, willow weed, yarrow
dicamba Banvel, Crop Care Dicamba, Kamba 500 Capeweed, chamomiles, chickweeds, cut-leaved geranium, dandelion group, docks, dove’s foot, mallows, mayweeds, Onehunga weed, pearlwort, pennyroyal, plantains, self-heal, shepherd’s purse, sheep’s sorrel, thistles, willow weed, wireweed, yarrow
ethofumesate Claw, Ethosin 500 SC, Expo 500, Nortron, Pasture Clear Chickweeds, mayweeds, Poa annua, summer grasses
ioxynil Totril Super Buttercups, chickweeds, dandelion group, field pansy, Onehunga weed, oxtongue, scarlet pimpernel, shepherd’s purse, speedwell, twin cress, willow weed, wireweed
mecoprop, dichlorprop, MCPA Turfclean Calandrinia, chamomiles, chickweeds, clovers, daisy, dandelion group, docks, mallows, Onehunga weed, pearlwort, plantains, scarlet pimpernel, shepherd’s purse, speedwell, storksbill, thistles, twin cress, willow weed, wireweed
mecoprop-P Compitone Plus, Duplosan-KV Chamomiles, chickweeds, clovers, dandelion group, docks, pearlwort, plantains, scarlet pimpernel, shepherd’s purse, speedwell, thistles, twin cress, willow weed, wireweed
picloram, triclopyr Tordon Gold Buttercups, chamomiles, chickweeds, clovers, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, dichondra, docks, dove’s foot, field pansy, horned oxalis, hydrocotle, mallows, mayweeds, Onehunga weed, oxtongue, parsley piert, pearlwort, pennyroyal, plantains, scarlet pimpernel, self-heal, sheep’s sorrel, shepherd’s purse, storksbill, thistles, twin cress, willow weed, wireweed, yarrow
triclopyr 600 EC Brush Off, Grazon, Scrubcutter, Victory Buttercups, chickweeds, clovers, cut-leaved geranium, daisy, dandelion group, hydrocotle, mayweeds, Onehunga weed, oxtongue, parsley piert, pearlwort, pennyroyal, scarlet pimpernel, thistles, twin cress, willow weed, wireweed, yarrow, Kikuyu (Victory only)

Soldier’s button (Cotula australis) White clover (Trifolium repens)
Catsear (Hypochoeris radicata) Dandelion (Taraxacum officinale)
Yarrow (Achillea millefolium) Cocksfoot (Dactylis glomerata)
Parsley piert (Aphanes spp.)
Mouse-ear chickweed (Stellaria media) Creeping oxalis (Oxalis spp.)
Broadleaf dock (Rumex obtusifolius) Californian thistle (Cirsium arvense)
Figure 7: Turf weeds.

Invertebrate pests

Ants

Ants can deposit small heaps of fine soil on the lawn surface as they remove soil particles to extend their underground nests. Brush the soil mound away when it dries. The ants can be killed with insecticides carbaryl, permethrin powder, or pyrethrins washed into the nest site with water.

Porina (Wiseana species)

Caterpillar feeding can be masked by nitrogen fertiliser application.

Grass grub (Costelytra zealandica)

Controlled by drenching insecticide into the soil. Sometimes heavy rolling or wheel pressure at the right time can crush grub larvae when they are feeding close to the surface. A biological control agent (Invade) is available commercially for grass grub.

Armyworms

Lawns containing couch, kikuyu and paspalum grasses are particular affected by the dark-brown caterpillars of the armyworm. They grow to 40 mm long feeding on leaves, stems and seed heads of the turf grasses. The can be controlled with carbaryl or trichlorfon.

Animal pests

Urine patches caused by dogs and cats can be dealt with culturally or with animal repellents. Dry soils and new lawns that attract cats can be wetted regularly to provide an unfavourable area for them. A thin layer of sawdust raked into the turf surface may prevent patches of lawn being ‘burnt’ by the high concentration of urine, as the microbes that colonise the wood particles utilise the surplus nitrogen, thereby attenuating urine’s toxicity. Repellents based on pepper dust or naphthalene need to be applied regularly, particularly after rain, and provide only temporary protection.

Acknowledgements

Thanks to Bill Walmsley, New Zealand Sports Turf Institute, for his article which was abridged for the section ‘Perennial Ryegrass for Lawns and Turf’, and Sam Wakelin for the drawings in Figure 1, Figure 2 and 3. Thanks also to Robert Lamberts for the photographs of weeds.

Vegetable

Weed and pest control

General

Various perennial weeds that can thrive in short regularly mown lawns can be troublesome. They usually originate from seeds carried by wind or birds. Once lawn weeds have germinated, mowing then rapidly spreads them. Thus, early treatment of the weeds is required to eliminate them from the lawn.

Some weeds, e.g. cape-weed (Arctotheca calendula) and daosoes (Bellis perennis), may look attractive in utility lawns, but are undesirable in high-quality lawns. In some regions they are declared as noxious weeds. Many weeds survive regular cutting, and so must be controlled with herbicides or by hand weeding.

The most troublesome lawn weeds are winter grass (Poa annua), nut grass (Cyperus rotundus), slender speedwell (Veronica filiformis), wax weed (Hydrocotyl americana) and baby’s tears (Soleirolia soleirolii). These persistent weeds are not controlled by herbicides registered for lawns. Moss may also be a problem.

Other lawn weeds that are less of a problem as they are controlled by herbicides include yarrow (Achillea millefolium), Mouse-ear chickweed (Cerastium glomeratum), bindii or Onehunga weed (Soliva pterosperma), broad-leaved plantain (Plantago major), self-heal (Prunella vulgaris), creeping buttercup (Ranunculus repens), Sheep’s sorrel (Rumex acetosella), lesser yellow trefoil or suckling clover (Trifolium dubium), and common white clover (Trifolium repens).

Good lawn care is an effective preventive measure. The presence of numerous weeds in a lawn usually indicates that the grass is not growing sufficient vigorously to prevent weeds from establishing. Low soil fertility and drought are the most common causes for poor growth of turfgrasses. Soil compaction and mowing the grass too short may also lead to invasion by moss.

Removing weeds

Hand weeding

Removing weeds by hand is effective for a few scattered rosetted weeds such as English daisy (Bellis perennis), dandelion (Taraxacum officinale), and plantains (Plantago spp.) Use a daisy grubber or hand fork to lift the weeds, and then firm back the displaced turf.

Moss

Moss is prevalent in lawns where soils are compacted, have poor drainage, low fertility, insufficient light, closely cropped cutting regimes, and too acidic or basic soils. Moss can be removed temporarily using a special herbicide containing benzalkonium chloride, copper sulfate or dichlorophen (Table 6), followed by scarification. Iron (ferrous) sulfate in lawn sands can also be used to eradicate moss.

However, unless the soil is in a condition conducive for healthy turf, the moss will return, necessitating removing the underlying cause of moss intrusion. Improving soil aeration, drainage and fertility, and top-dressing on light soils to assist in water retention, could improve lawn health. Adopting an annual maintenance programme (Table 4) will alleviate moss invasion.

Herbicides

The herbicides registered for use in turf and the weeds they control are listed in Table 1. They are selective for specific weeds, and usually do not harm the turf grasses when applied at recommended rates to lawns more than six months old. Higher rates may kill even a mature lawn. Younger turf may be susceptible to herbicides, even when they are applied at rates recommended on the label.

The herbicides translocate within affected plants from the leaves to the roots. Within a few days of application, the weeds usually begin to distort and shrivel.

Proprietary lawn herbicides often combine two or more active ingredients in order to control the widest possible range of weeds in one application. Active ingredients that are commonly mixed include 2,4-D, which is selective against broad-leaved rosetted weeds. Mecoprop kills small-leaved and creeping weeds such as clovers (Trifolium spp.) and yarrow (Achillea millefolium). Dicamba may be combined with 2,4-D or MCPA to widen the spectrum of control. Bromoxynil is usually combined with MCPA or dicamba to control Onehunga weed.

Application

Apply the selected herbicide to a lawn in spring, about two to three weeks after growth commences, when plant growth is vigorous. Then, weeds are more susceptible to the effects of the herbicide, and the grasses will rapidly colonise the spaces vacated by the dead weed plants.

Allow at least three days after mowing before applying the herbicide, to allow enough time for the weeds to develop new leaf surfaces to absorb the herbicidal compounds. Further, wait three days after herbicide application before mowing the lawn to allow time for the herbicide to translocate to the roots.

Lawn weeds differ in their susceptibility to herbicides. Dandelions and plantains can be killed after one to two applications. Clovers may require two to three applications at four to six-week intervals. Creeping speedwell (Veronica persica) may survive several applications.

Check label for instructions on disposal of lawn clippings. For some herbicides such as chlorpyralid, clippings should not be added to compost heaps that are used as mulch around sensitive plants, or disposed of at any garden waste recycling centre. In such a case, clippings should be mulched back into the lawn, or burnt.

Table 1: Herbicides registered for control of weeds in turf lawns.

Active ingredient Trade name Weeds controlled
methylarsinic acid AGPRO MSMA 600 Paspalum, summer grasses
bromoxynil, ioxynil, mecoprop Axall Allseed, buttercups, calandrinia, capeweed, chamomiles, chickweeds, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, dichondra, docks, dove’s foot, field pansy, henbit, mayweeds, Onehunga weed, oxtongue, parsley piert, plantains, portulaca, pratia, scarlet pimpernel, shepherd’s purse, speedwell, starweed, thistles, twin cress, willow weed, wireweed
2,4-D, dicamba Banvine Chamomiles, chickweeds, clovers, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, docks, dove’s foot, henbit, mallows, Onehunga weed, oxtongue, parsley piert, pennyroyal, plantains, scarlet pimpernel, shepherd’s purse, storksbill, thistles, twin cress, willow weed, wireweed, yarrow
bentazone Basagran Buttercups, calandrinia, chamomiles, chickweeds, cotula, mayweeds, Onehunga weed, parsley piert, plantains, scarlet pimpernel, shepherd’s purse, storksbill, willow weed
benzalkonium chloride, copper sulfate Mossoff Algae, lichen, liverworts, moss
dichlorophen Mostox Algae, lichen, liverworts, moss
benzalkonium chloride Yield Algae, lichen, liverworts, moss
chlopyralid Tango, Versatill, Void Chamomiles, clovers, cudweed, daisy, dandelion group, docks, mayweeds, Onehunga weed, oxtongue, thistles, willow weed, yarrow
dicamba Banvel, Crop Care Dicamba, Kamba 500 Capeweed, chamomiles, chickweeds, cut-leaved geranium, dandelion group, docks, dove’s foot, mallows, mayweeds, Onehunga weed, pearlwort, pennyroyal, plantains, self-heal, shepherd’s purse, sheep’s sorrel, thistles, willow weed, wireweed, yarrow
ethofumesate Claw, Ethosin 500 SC, Expo 500, Nortron, Pasture Clear Chickweeds, mayweeds, Poa annua, summer grasses
ioxynil Totril Super Buttercups, chickweeds, dandelion group, field pansy, Onehunga weed, oxtongue, scarlet pimpernel, shepherd’s purse, speedwell, twin cress, willow weed, wireweed
mecoprop, dichlorprop, MCPA Turfclean Calandrinia, chamomiles, chickweeds, clovers, daisy, dandelion group, docks, mallows, Onehunga weed, pearlwort, plantains, scarlet pimpernel, shepherd’s purse, speedwell, storksbill, thistles, twin cress, willow weed, wireweed
mecoprop-P Compitone Plus, Duplosan-KV Chamomiles, chickweeds, clovers, dandelion group, docks, pearlwort, plantains, scarlet pimpernel, shepherd’s purse, speedwell, thistles, twin cress, willow weed, wireweed
picloram, triclopyr Tordon Gold Buttercups, chamomiles, chickweeds, clovers, cotula, cudweed, cut-leaved geranium, daisy, dandelion group, dichondra, docks, dove’s foot, field pansy, horned oxalis, hydrocotle, mallows, mayweeds, Onehunga weed, oxtongue, parsley piert, pearlwort, pennyroyal, plantains, scarlet pimpernel, self-heal, sheep’s sorrel, shepherd’s purse, storksbill, thistles, twin cress, willow weed, wireweed, yarrow
triclopyr 600 EC Brush Off, Grazon, Scrubcutter, Victory Buttercups, chickweeds, clovers, cut-leaved geranium, daisy, dandelion group, hydrocotle, mayweeds, Onehunga weed, oxtongue, parsley piert, pearlwort, pennyroyal, scarlet pimpernel, thistles, twin cress, willow weed, wireweed, yarrow, Kikuyu (Victory only)

Soldier’s button (Cotula australis) White clover (Trifolium repens)
Catsear (Hypochoeris radicata) Dandelion (Taraxacum officinale)
Yarrow (Achillea millefolium) Cocksfoot (Dactylis glomerata)
Parsley piert (Aphanes spp.)
Mouse-ear chickweed (Stellaria media) Creeping oxalis (Oxalis spp.)
Broadleaf dock (Rumex obtusifolius) Californian thistle (Cirsium arvense)
Figure 7: Turf weeds.

Invertebrate pests

Ants

Ants can deposit small heaps of fine soil on the lawn surface as they remove soil particles to extend their underground nests. Brush the soil mound away when it dries. The ants can be killed with insecticides carbaryl, permethrin powder, or pyrethrins washed into the nest site with water.

Porina (Wiseana species)

Caterpillar feeding can be masked by nitrogen fertiliser application.

Grass grub (Costelytra zealandica)

Controlled by drenching insecticide into the soil. Sometimes heavy rolling or wheel pressure at the right time can crush grub larvae when they are feeding close to the surface. A biological control agent (Invade) is available commercially for grass grub.

Armyworms

Lawns containing couch, kikuyu and paspalum grasses are particular affected by the dark-brown caterpillars of the armyworm. They grow to 40 mm long feeding on leaves, stems and seed heads of the turf grasses. The can be controlled with carbaryl or trichlorfon.

Animal pests

Urine patches caused by dogs and cats can be dealt with culturally or with animal repellents. Dry soils and new lawns that attract cats can be wetted regularly to provide an unfavourable area for them. A thin layer of sawdust raked into the turf surface may prevent patches of lawn being ‘burnt’ by the high concentration of urine, as the microbes that colonise the wood particles utilise the surplus nitrogen, thereby attenuating urine’s toxicity. Repellents based on pepper dust or naphthalene need to be applied regularly, particularly after rain, and provide only temporary protection.

Acknowledgements

Thanks to Bill Walmsley, New Zealand Sports Turf Institute, for his article which was abridged for the section ‘Perennial Ryegrass for Lawns and Turf’, and Sam Wakelin for the drawings in Figure 1, Figure 2 and 3. Thanks also to Robert Lamberts for the photographs of weeds.

Tomatoes

Tomatoes (Lycopersicon esculentum) belong to the Solanaceae family, which includes potatoes, capsicums (peppers), eggplant, cape gooseberry and tamarillo, as well as the nightshade weeds. Botanically, tomatoes are classified as a fruit because the edible portion is a giant berry.

History

Tomatoes originated from South America, most likely the Peru region, where they were cultivated as early as 700 AD. It is thought that Spanish explorers brought them to Europe, with the first mention of tomatoes in literature being in 1544. This described a pomi d'oro (golden apple) that was eaten in Italy with oil, salt and pepper. The English regarded the tomato with suspicion for many years, considering the bright red colour to be a danger signal. In New Zealand tomatoes were grown in home gardens from the late 1800s.

Interesting fact

In the mid-1990s over 600 varieties of tomatoes were commercially available in the US and Canada, and 2500 varieties were kept as seed in a gene bank in Gatersleben, Germany.

Tomato cultivars in New Zealand

There is a bewildering assortment of tomato varieties available. Below are a number of different types of tomatoes.Select several different varieties to grow in the garden that will suit your climate and requirements for tomatoes.

Classifying tomato cultivars
Tomatoes can be categorised as determinate or indeterminate. Determinate tomatoes (also called bush or dwarf tomatoes) grow to a certain size and then begin to flower, producing a single crop that is harvested once. These are very useful for commercial growers. In-determinate tomatoes (also called vine or cordon tomatoes) grow stems and produce flowers at the same time. They need staking and are useful in the home garden as they produce fruit over a long period of time.

Heirlooms and hybrids
Tomatoes can also be divided into heirloom or hybrid varieties. Heirloom tomatoes are old varieties that have been around for a long time, and many of them have very good flavour but may have less disease resistance and a greater tendency to develop physiological disorders than modern varieties. The modern hybrids have been bred for characteristics such as consistency in colour, shape and size, long shelf-life, high yield, uniform ripening and disease resistance.

End uses
Tomato varieties can be categorised by their end use. For example, plum tomatoes are used for canning and have thick flesh and reduced amount of pulp. Beefsteak tomatoes (e.g. Big Beef) are very large and also have reduced pulp, which makes them excellent for sandwiches and sauces. Salad or classic tomatoes are juicy as they have a lot of pulp but this tends to fall out when they are sliced.

Nutritional value

Tomatoes are considered to be one of the most important vegetables in the western diet, based on the amount consumed and the vitamins and minerals supplied. Particularly important are vitamins A and C. At around 22 mg vitamin C/100 g, tomatoes are considered to be a good source of this important nutrient. Tomatoes are also high in carotenoids, such as beta-carotene, which is one of the precursor molecules to
vitamin A.

Another important carotenoid in tomato is lycopene, which is responsible for the bright red colour. Lycopene is a potent antioxidant and a number of recent studies have linked high intakes of lycopene with a reduced risk of cancer, particularly prostate cancer. Lycopene is also thought to have a role in preventing degeneration of the eyes and may help in protecting the skin from ultra-violet light damage, while eating tomato-based foods has been associated with a reduced risk of heart disease.

Pests and Diseases

A typical home garden may include only 5-10 tomato plants. There is no opportunity for replanting if a plant is lost in January and this will lead to the loss of a significant proportion of the crops. Therefore it is very important to monitor established tomatoes plants regularly and act quickly if there are symptoms of pests or diseases. Some of the more important pests and diseases are described below but first we will look at how the principles of Integrated Garden Management (IGM) can be used to grow healthy tomatoes.

Integrated Garden Management for tomatoes

IGM techniques initially rely on preventing pests and diseases attacking the tomato plants. This is not always possible so the tomatoes should be watched closely during growth for the first signs of pests or disease. Once the pest or disease has been identified, an appropriate control technique should be selected. This may involve more than one method and will not necessarily involve the application of chemicals. Chemical control can be very effective for large areas, e.g. a processing tomato crop, or when a pest or disease attack is particularly severe. However, in home gardens, the application of chemicals, especially insecticides, can upset the ecological balance within the garden and lead to further outbreaks of other pests and diseases. IGM techniques useful for growing tomatoes. These include crop rotation, resistant cultivars, seed treatment, weed control, fertiliser, irrigation, biological control and chemicals.

For more information an integrated garden management and specific pests and diseases, see More info.

A final note

In the home garden, especially where IGM principles are applied, pests and diseases rarely cause problems. Your tomato-growing efforts will be rewarded in the summer with bowls of fresh juicy salad tomatoes, tasty tomato sandwiches and delicious sweet treats of cherry tomatoes. In the winter, reach for the jars of dried tomatoes in olive oil, tomato chutney, tomato sauce, tomato relish and tomato soup, and plan what cultivars you will plant next year.

Carrots

Carrot plants are biennial plants (plants that live for two years) that produce and store sugars in their roots. This accumulated sugar tends to expand the root, forming what is called the taproot, which is better known to us as the carrot or Daucus carota.
Carrots have probably been eaten for thousands of years, especially as medicinal herbs. They were most likely first grown by farmers in modern day Afghanistan over a thousand years ago. The earliest carrots were generally purple or yellow and varied in taste and size. Centuries later, purple carrots have been almost completely replaced by the now familiar orange carrot, which is rated the third most popular vegetable in New Zealand.
The two most recommended types of carrots for home gardening are Nantes or Chantenay varieties. When these are homegrown, they are generally more flavoursome, colourful, and more nutritious than most commercially grown carrots.
Nutritional value of carrots
Carrots have the highest vitamin A content of all vegetables. One medium carrot supplies enough beta-carotene for the body to make two days supply of vitamin A. They also contain antioxidants, which protect our immune system by absorbing free radicals in our body. Carrots also have a greater antioxidant effect when cooked. Cooking changes the chemical nature of these compounds, making them more effective antioxidants.
Carrots are also an excellent source of phytochemicals, including alpha and beta-carotenes and lycopene. Many of these protect against cancer. They also supply us with useful amounts of fibre, vitamin C, and vitamin B. In addition, carrot skins also have high levels of nutrients, which is a good reason not to peel carrots unless it is really necessary.
Scientific advice on carrot growing
The best time to sow carrots is in early spring and summer, between September and February. Also remember that sites for planting carrot seed should be sunny, with a soil pH of around 6.5. The site also needs to be well drained, and do try to avoid sites with compact layers of stones or lumps which may restrict root penetration.

Carrot Fritters
1 tsp salt
1½ tsps ground cumin
1½ tsps ground coriander
½ tsp ground turmeric
½ tsp cayenne pepper
150 g plain flour
½ cup beer
1 egg, whisked
1 cup packed grated carrot
6 spring onions, finely chopped
oil for frying
1 bunch coriander
Mix salt, spices and flour in a bowl. Make a well in the centre and pour in beer, egg, carrot and spring onion. Mix well. Pour 1 cm oil into a heavy based frying pan and fry spoonfuls of mixture until golden on both sides - around 5 minutes. Drain on kitchen paper and serve garnished with coriander and a dipping sauce of garlic, mint and yoghurt.

Potatoes

Potatoes (Solanum tuberosum subspecies tuberosum) belong to the Solanaceae family that includes other important vegetables, such as tomatoes, eggplants and capsicum peppers, as well as some common weeds including nightshade and tobacco. The potato tubers are actually swollen stems that grow under ground.

History

Potatoes originated in the South American countries of Peru and Bolivia. The earliest record of potatoes in Europe comes from Spain and is dated 1573. By the 17th century it had become an important food crop in Europe especially among the poor.

Interesting fact

The potato is the fourth most widely grown food plant in the world after wheat, corn and rice. Worldwide 300 million tonnes are produced each year. A field of potatoes produces more calories and protein, more quickly, than any other crop.

Popular potato cultivars in New Zealand

These potatoes are generally available to home gardeners?

Early maturing cultivars that are usually best dug immature and eaten immediately.

Cliffs Kidney: requires fertiliser and water to get the numerous kidney-shaped tubers to a good size.
Jersey Benne: as for Cliffs Kidney
Liseta: vigorous variety with large, yellow-fleshed tubers.
Swift: produces very little top growth but has very early yields of oval, cream-fleshed tubers.
Mid-season cultivars that can be dug immature or left till mature

Ilam Hardy: probably the easiest variety to grow but better suited to earlier harvest as it can become misshapen if left for maximum yield.
Driver: good eating quality
Maris Anchor: best as either an early crop or left to fully mature and has a reputation for good eating.
Desiree: a popular general-purpose red-skinned variety.
Karaka: a vigorous grower that is prone to tuber cracking under some conditions but has exceptional flavour as a boiled potato.
Nadine: needs good growing conditions to yield well; although its lack of taste may not appeal to all, it is attractive and boils well.
Main crop cultivars that are best left to fully mature – suitable for storing

Rua: a very late maturing cultivar; probably the best available for long term storage.
Moonlight: a recent release that is rapidly increasing in popularity due to heavy yielding ability and good flavour.
Red Rascal: a high yielding red-skinned cultivar with good eating quality and medium–long storage.
Agria: the most popular yellow-fleshed cultivar with a reputation for good flavour.

Nutritional Value

New Zealanders consume about 60 kg of potatoes per person every year. While potatoes are a primary source of carbohydrate they also contain significant amounts of other minerals and vitamins. Many of these minor elements are in a readily digestible form, which makes their contribution to the diet even more important.

Pests and Diseases

Like any plant the potato is subject to various pests and diseases, although in New Zealand there are few pests of consequence. Diseases that destroy leaves affect tuber growth by reducing the ability of plants to photosynthesise, while those diseases that damage the stem disrupt the transport of nutrients from the leaf to the tuber. Other diseases infect the tuber causing rots.

Integrated Garden Management for potatoes

While chemical formulations are available for control of most pests and diseases they are often not the most practical solution in a small garden. In addition, many home gardeners prefer to use non-chemical methods of control. Successful control requires an understanding of the life cycle, environmental requirements and the level of damage caused by the pest or disease. Prevention is usually the first line of defence against pests and diseases, followed by early observation and identification. Integrated Garden Management (IGM) techniques can then be selected and applied in a multi-pronged approach towards control. These include crop rotation, choosing resistant cultivars, altering planting and harvesting dates, sowing clean seed tubers, controlling weeds, managing crops properly, applying sufficient fertiliser and water, utilising biological control agents and applying chemicals.

For more information on integrated garden management and specific pests and diseases, see More Info.

A final word

The potato is not a humble vegetable as is often quoted. It is a fascinating crop to grow and rewards the grower with a high yielding, nutritious, versatile food. For those with a small garden try growing potatoes in car tires. Start with a couple of tires stacked up and filled with compost. Plant two or three seed tubers and as the plant grows add tires and cover the base of the plant with more compost and soil. Keep up the water and nutrients and see if you can approach the reported yield of over 15 kg of potatoes!