quaking grass, (genus Briza), genus of four species of slender annual or perennial grasses in the family Poaceae, native to Eurasia. Quaking grasses are so named for the spikelets of open flower clusters and dry seedheads, borne on long stalks, that quiver in even slight breezes. Most are cultivated as ornamentals, including big quaking grass, or rattlesnake grass (Briza maxima), perennial quaking grass (B. media), and little quaking grass, or shivery grass (B. minor).