Downy brome is a winter annual. It germinates in the fall, over winters as a seedling, then flowers in the spring. If fall precipitation is limiting and spring moisture is adequate, the seeds will germinate in the spring, and the plants will flower that summer. The plants typically flower from mid-April through June. Florets are dispersed within a week of maturity by wind, attachment to animal fur, or small rodents.
Seeds move as a contaminant in hay, grain, straw, and machinery.
An abundant seed producer, downy brome has been reported as having a production potential in excess of 300 seeds per plant. Seed production per plant is dependent on plant density. Plants as small as 2.5 cm in height may produce seed. Seeds will maintain a high viability in dry storage, lasting in excess of 11 years. In the field, under buried conditions, seeds will loose their viability in 2 to 5 years.