Rye Grass, a group of annual and perennial grasses of the Old World. Rye grasses have flat, shiny, dark-green or blue-green leaves. Their flowers are borne in long, flat, two-rowed spikes. Two species, English, or perennial, and Italian, are cultivated as lawn and pasture grasses in North America. English rye grass grows to 24 inches (60 cm) tall; Italian, to 30 inches (90 cm). Darnel is a common rye-grass weed of grain fields.

Rye grasses belong to the genus Lolunn of the grass family, Gramineae. English is L. perenne; Italian, L. multiflorum; darnel, L. temulentum.