Roses

Modern roses

The original species of wild rose had a single flower with five (or in some cases four) petals and grew across all of the continents in the Northern Hemisphere.

The first garden roses probably first occurred in the Middle East, spread throughout ancient Greece and Rome, and eventually across Europe. These roses were in groups we now call gallica r oses, damask roses and alba roses.

Around 1800 a small group of four China roses arrived in Britain. They are valued for their ability to flower repeatedly throughout the summer. These were successfuly interbred over the years to eventually produce the hybrid tea.

In 1870s a French breeder produced a new group called polyantha roses. Polyanthas were then crossed with hybrid teas resulting in a new group called floribunda roses.

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Growing roses throughout the year

Roses benefit from regular attention. Winter is ideal for planting and pruning, spring for mulching and fertilising, summer for irrigating and weeding, and autumn for continued deadheading and preparing new planting sites.

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Integrated pest management spray programmes

When developing an IPM or organic spray programme, one easily made mistake is to continue the old calendar spray philosophy but substitute `chemicals' with more user-friendly substances. Many factors need to be taken into consideration when managing the pests and diseases on your rose plants:

• identify the pests and diseases present on the plants,
• seek information on the life cycles of all the pests and diseases present,
• identify any natural beneficial insects that are present,
• seek information on the life cycles of natural beneficial insects present.

Weather patterns can also have a major influence on the occurrence of diseases.

Because most fungicides are preventive, the key period to control diseases is in the spring/early summer (September to December). By keeping infection levels low during this period, control is not as critical later in the season.

Rose varieties differ in their susceptibility to diseases so identify those that grow best and replace disease-prone varieties.

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Diseases

Fungal diseases present the biggest concern to the rose grower. Of the 13 different fungal diseases of roses listed in New Zealand (Pennycook 1989) six cause the most serious problems.

Listed in order of importance they are:

• Rust Phragmidium mucronatum
• Black spot Diplocarpon rosea
• Powdery mildew Sphaerotheca pannosa
• Downy mildew Penonospora sparsa
• Grey mould Botrytis cinerea
• Silver leaf Chondostereum purpureum.

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Pests

Pests in order of importance:

• aphids
• two spotted mite.

Fertilisers

Seaweed that is applied to deter insects also acts as a liquid fertiliser.

The following fertilisers can be applied before and during the growing season:

• Base dressing in spring (September):
  • Gypsum
  • Dolomite
  • Potassium sulfate
  • Blood and bone
• Side dressings
  • At the start of and after each flowering flush (early December to the end of February) use three-month slow release fertilisers.

Happy rose gardening!

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