wheat grass, any plant of the genus Agropyron, cool-season perennials of the family Gramineae (grass family). Species of wheat grass, both native and introduced, are important range forage grasses in the prairie states. Wheat grasses are also valuable for revegetation because of their drought resistance and winter hardiness. Important species are the crested wheat grass ( A. cristatum ), introduced from N Russia, and the native Western wheat grass ( A. smithii ). The weed quack grass also belongs to this genus. Wheat grass is classified in the division Magnoliophyta, class Liliopsida, order Cyperales, family Gramineae.