Managing seedling recruitment
The right paddock: Choose paddocks with at least 10% perennial ryegrass or cocksfoot in winter or early spring.7
Preparation: Maintaining herbage mass at around 1,000kg DM/ha (height 3cm) during winter, ensures plants are not overgrazed and maximises the number of tillers (stems) which can be exposed to vernalisation conditions (a period of short days and low temperatures, followed by long days), which triggers tillers to become reproductive. If annual weeds dominate the pastures, clean-up strategies such as spray-grazing or winter cleaning may be needed to reduce competition.
In early spring, maintain herbage mass between 1,200 to 2,000kg DM/ha to encourage tillering of ryegrass and cocksfoot. This will lead to greater seed head production.
Lock it up: Spell the pasture from flowering (anthesis) until the seed has ripened and has been shed from the stem. Seed growers wanting to maximise seed production normally lock up at the start of stem elongation in mid-September. For livestock producers some of the earlier seed heads can be eaten. Follow-up resting enables the rest of the plants to develop seed heads. This keeps pasture digestibility higher for longer and extends the grazing time.
Flowering: The success of the technique is reliant on achieving ample seed production before the season finishes. In dry springs or where there is no moisture to support seed production in late or very late-maturing cultivars, this technique is unlikely to result in adequate recruitment.
Time of flowering is cultivar and season-dependent, but typically occurs around mid to late November with seed ripening usually finished by early January. To identify flowering, inspect the seed heads and look for the appearance of anthers (flowers) on the plant.
In perennial ryegrass, seed head emergence can signal flowering will occur in approximately 40 days.
Flowering time (anthesis) of different perennial ryegrass cultivars can vary by up to six weeks. In very early flowering varieties, such as ‘Fitzroy’, approximate flowering time is mid-November but very late flowering varieties, like ‘Bealey’, may not flower until Christmas.
A prolonged seeding period will improve the chances of recruitment. The length of heading is commonly longer or more staggered in older cultivars. Newer cultivars, which have been bred to maximise vegetative growth, tend to have more compressed heading periods. Referred to as ‘low aftermath’ heading, the plants run to head all at once, which shortens the seeding period.
Extended aftermath heading is thought to partly explain the persistence of older types of ryegrasses (such as ‘Victorian’) in long-term pastures. They set seed over a longer flowering period, meaning an increased chance some seeds may escape removal by grazing or hay cutting and remain to germinate the next autumn.