Ryegrass variety development in the U.S. has concentrated on improving forage yield, seed production, disease resistance and cold tolerance. Through plant breeding and selection, annual ryegrass has become a highly valued and productive cool-season forage. Plant Description Annual ryegrass is a bunch type grass that tillers profusely. The plant appears shiny, dark green and grows to a height of 2 to 5 feet. It has a deeply fibrous root system, erect culms, glabrous leaves and a spike-type inflorescence.
Awns are usually present and attached to the lemma.
While annual ryegrass is generally considered to be an annual species, it has on occasion behaved as a short term perennial or biennial. It does exhibit a response to day-length, and flowering habit varies with variety and latitude. There are both diploid and tetraploid cultivars. Tetraploid cultivars have twice as many chromosomes as diploid types, wider leaves and appear more robust. Recent yield data suggests that newer tetraploid cultivars are at least equal to, and may have some yield advantage over, their diploid relatives.