The true grasses are monocot (Liliopsida) plants of the family Poaceae (formerly Gramineae). The family includes lawn and forage grasses, bamboo, wheat, rice, rye, corn, sugarcane, and numerous other species of considerable ecological and economic importance. Agricultural grasses grown for food production are called cereals.
Grasses are generally characterized by the following:
- Hollow stems (called culms), plugged at intervals by nodes.
- Leaves, arising at nodes, are alternate, distichous (in one plane) or rarely spiral.
- Leaves are differentiated into a sheath hugging the stem for a short distance and a blade with margin usually entire; a ligule (a membranous appendage or ring of hairs) lies on top at the junction between sheath and blade.
- Flowers are small, without petals, borne clustered in an inflorescence, often a spike or tassel, and wind-pollinated.