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. Seeds can withstand extremely high soil temperatures.
Seeds germinate the best in the dark or in diffuse light.
They do not need to be in contact with bare soil to germinate, and a litter cover generally will improve germination. However, seeds will germinate more quickly when covered with soil. Seedlings rapidly emerge from the top 2.5 cm of soil, and a few plants emerge from depths of 8 cm. No emergence occurs from seeds buried 10 cm below the surface. Downy brome possesses an extensive root system that grows through the spring.