Bromus inermis Leyss. Smooth brome is a strongly rhizomatous, sod-forming perennial grass.
Sheaths are round and glabrous.
Two subspecies are recognized. The more common Bromus inermis Leyss. Bromus inermis Leyss. In addition to these two subspecies, over 30 varieties have been described. Smooth brome was introduced from Eurasia into the United States in 1884 by the California Experiment Station.