Perennial ryegrass is the most common pasture grass in New Zealand due to its easy establishment, management, and adaptability to a range of soil fertilities and environmental conditions. Perennial ryegrass is also compatible with a range of clover and pasture species. Endophyte status is a key consideration when selecting perennial ryegrass cultivars, along with flowering time. Generally, spring production will be earlier for earlier flowering cultivars, but the feed quality will be compromised with the early emergence of seed heads. Ryegrass cultivars also vary according to the chromosome number classified as diploid or tetraploid.