Grass is an angiosperm, which means it is a flowering plant, although the flowers are small, green and inconspicuous. Grass flowers are wind pollinated and the seeds are dispersed by wind, water, by birds and on the coats and sometimes in the digestive systems of animals. However, grass can also spread by tillering; this means it can spread laterally by producing side shoots over ground or roots underground that produce new plants. This is why grass can persist even if it is cut or grazed and never gets the chance to set seed.The angiosperms are divided into two groups; monocotyledons, which produce seedlings with a single leaf, such as grasses and dicotyledons, which produce seedlings with two leaves.Grasses can be annual, biennial or perennial and this governs their growth habit and persistency. Different species flower at different times of the year, with the majority of British grasses flowering in May, June and July. Preventing flowering by removing the grass stem, by grazing or cutting, causes the plant to reproduce vegetatively by tillering; this produces a leafier, denser sward than one that is allowed to flower and set seed.

Most of the nutritional value of grass is in the leaf, and grass is at its most nutritious and with the highest moisture content early in the growing season. However, total yield and % dry matter increases over the season, until the plants die back in winter.Particularly when cutting for conservation, a balance needs to be struck between nutritional value and yield – cutting early will give low yields of highly nutritious fodder with a low dry matter content; cutting late, when much of the grass has gone to seed, will give high yields of poorer quality fodder with high dry matter. Allowing the grass to seed also adversely affects the density of the sward, and therefore its ability to withstand adverse conditions.