Downy brome

Bromus tectorum

Bromus tectorum is an annual bunchgrass, usually germinating in autumn, overwintering as a seedling, then flowering in the spring or early summer. If winter rainfall is limiting and spring moisture is adequate, the seeds will germinate in the spring, and the plants will flower that summer. It typically reaches 40–90 centimetres (16–35 in) tall, though plants as small as 2.5 centimetres (0.98 in) may produce seed. It is cleistogamous and self-fertile, with no evident out-crossing.
It has an extensive root system. The wide-spreading lateral roots are one of the keys to the survival of this plant. A study showed that it had the capability to reduce soil moisture to the permanent wilting point to a depth of 70 centimetres (28 in), reducing competition from other species.