[Cal-IPC] Invasive: Avena barbata (slender wild oat) is a winter annual grass (family Poaceae) that grows in nearly every grassland area of the state. It does well in sandy/poor soils, often on the road verges. It is one of the annual grasses that was introduced as a forage species and has replaced the native perennial grasses. Cal-IPC Rating: Moderate (link added by Mary Ann Machi)

[Wikipedia] Central Asia & Mediterranean Basin Native, Noxious Weed: A. barbata is native to central Asia (as far east as Pakistan) and the Mediterranean Basin. As an introduced species it also occurs in other Mediterranean-like habitats of New Zealand, Australia, South Africa, Argentina, Chile, Brazil, and Uruguay. In Europe it has been reported in Finland, France, Germany, Norway, Bulgaria, and Austria. In North America it is an introduced species and noxious weed, where it is especially widespread in California. In California it has displaced native species of grass.[4] It is also found in Oregon, Washington, Hawaii, Massachusetts, Nevada, Arizona, and New Mexico. (link added by Mary Ann Machi)