Bromus tectorum is an erect-stemmed annual grass that grows to about 8-25 in. (20-70 cm) in height.
Foliage
The leaf sheaths and blades are covered with soft short hairs. The leaves are 0.08-0.16 in. (2-4 mm) wide and up to 8 in. (20 cm) long. Its ligules are 0.04-0.1 in. (1-2.5 mm) long.
Flowers
The panicles measure 2-7.75 in. (5-20 cm) long, have numerous branches, retain an open quality and are generally nodding. The panicles bear from 3 to 8 drooping spikelets, each spikelet is 0.8-1.4 in. (2-3.5 cm) long. The glumes are awl-shaped. The lemmas are narrowly lanceolate, 0.04-0.06 in. (1-1.5 mm) wide, toothed, and sometimes hairy. They have slender, straight awns that are 0.4-0.67 in. (10-17 mm) long. Flowering occurs from May to June.
Fruit
The seeds can germinate in the fall or in the spring; fall germination is generally more common. B. tectorum has a fibrous root system is finely divided. When a seed germinates in the fall, the developing root system is able to expand over the winter, giving the plant an increased ability to exploit available water and nutrients in the spring.
Ecological Threat
Bromus tectorum has the ability to draw down soil moisture and nutrients to very low levels, making it difficult for other species to compete. An increased cycle of fires favors annual species at the expense of many perennials. Due to its tendency to mature early and then dry out, it gains a competitive advantage through the promotion of fire. It is an agricultural, nursery and orchard pest.