Perennial Ryegrass Perennial Ryegrass is recognised as being one of the most valuable pasture grasses for temperate regions of the World. Perennial Ryegrass produces a large amount of high quality feed if conditions are favourable during the growing season. Its main growing season is from the autumn break until late spring, but it can provide useful growth during the rest of the year if the season is extended by irrigation or summer rains. Most cultivars make limited growth in the winter, and summer growth may be restricted by high temperatures even if sufficient moisture is available.
Hybrid ryegrass Hybrid Ryegrass is derived from crosses between perennial ryegrass and Italian ryegrass. Perennial type hybrids have a more perennial component than Italian ryegrass in their breeding. They are generally capable of 2-3 years production with potential for extended life under good management and seasonal conditions. Italian type hybrids have less perennial component and more exhibit the benefits and characteristics of Italian ryegrass and are capable of contributing outstanding production for 1-2 years
Italian ryegrass Typically a biennial, but cultivars exist that are strictly annuals. (Westerwolds ryegrasses) and others that can persist for three to four years have been developed. Its growing season is autumn, winter, spring, with some growth in summer if sufficient moisture is available. Italian Ryegrass is particularly valued because of its good winter growth – its winter production is much greater than that of Perennial Ryegrass – and its high nutritive value.
Diploid/tetraploid ryegrasses Perennial, Italian and Hybrid ryegrass occur both in the naturally evolved, diploid form (14 chromosomes), and a tetraploid form (28 chromosomes). The chromosome number has been doubled, by treating the diploids with the chemical colchicine. “Tetraploiding” ryegrass produced changes in anatomical, chemical and physiological makeup. For example, plants have larger parts, such as tiller and leaf size; they have higher moisture and carbohydrate content; they grow at a faster rate; mature earlier and are shorter lived. The value of tetraploids are increased yield at specific times of the year (typically winter) and increased stock utilization. Tetraploid hybrid, Italian and perennial ryegrass is often direct drilled into existing pastures as a method of boosting productivity during late autumn to mid-spring. They are a better alternative for annual silage production. Tetraploids are best suited to conditions of high fertility, moist or irrigated conditions and lax grazing management. In contrast diploid ryegrass is suitable for hay production over multiple years and is better suited to drier conditions and close grazing. Less cell wall (cellulose) but more carbohydrate means that dry matter production of Tetraploid Ryegrasses is of higher quality and the grass is more palatable.