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.

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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.

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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.

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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.

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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?

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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.
  

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