The cultivated cereal oat, an erect cool-season annual grass grown for grain, forage, and — increasingly in gardens — as a fast, soil-building cover crop. From a spring or late-summer sowing it shoots up to 2-4 feet of slender, upright culms topped by an open, airy seed head (a spreading panicle) whose dangling spikelets ripen from green to gold. Domesticated in the Old World from wild oats, it is not a native wildflower but a true annual crop: it germinates fast, smothers weeds, builds biomass, and in cold zones conveniently winter-kills to leave an easy mulch in spring. Gardeners reach for it most as a green manure and erosion-stopping nurse crop, and for the soft, grassy texture and ripening-gold seed heads it adds while it grows.