About Bromus rubens L.
Bromus madritensis is a winter annual grass that grows either as solitary plants or in tufts, with erect or ascending culms that reach 20–70 cm (7.9–27.6 in) in height. Its leaf sheaths are downy or slightly hairy. This grass does not have auricles, and its glabrous ligules measure 1.5–2 mm (0.059–0.079 in) long. Its flat leaf blades are either glabrous or slightly hairy, and grow 4–20 cm (1.6–7.9 in) long and 1–5 mm (0.039–0.197 in) wide. The plant produces erect, ellipsoid panicles that are 3–12 cm (1.2–4.7 in) long and 2–6 cm (0.79–2.36 in) wide, with short branches that ascend and spread slightly. The branches never droop, and each bears one or two spikelets. The spikelets are 4–6 cm (1.6–2.4 in) long, longer than the panicle branches, and hold seven to eleven florets. Spikelet color ranges from green to distinctly purplish-red. The lightly hairy glumes taper at their ends and have translucent margins. Lower glumes are one-nerved and 5–10 mm (0.20–0.39 in) long, while upper glumes are three-nerved and 10–15 mm (0.39–0.59 in) long. Glabrous, slightly rough lemmas measure 1.5–2 cm (0.59–0.79 in) long; lemmas are hairier toward their edges and have five to seven veins. The awns are roughly the same length as the lemmas, at 1.2–2.3 cm (0.47–0.91 in) long, and curve slightly. Anthers measure 0.5–1 mm (0.020–0.039 in) long, and caryopses can reach up to 11 mm (0.43 in) long. This grass emerges in early winter and stays dormant until spring, when heavy rainfall and warmer temperatures stimulate its growth. It typically flowers from this growing period until May, when water stress stops its growth. Population sizes increase during periods of heavy rainfall, and entire populations can be killed off during extended drought. This grass changes soil conditions, and its competitive pressure negatively impacts native plant populations. Its highly flammable tissue also contributes to wildfires in North American plant communities where fire was previously rare. Dry florets of this weed tangle in animal fur and can tear the digestive tracts of foraging livestock. Bromus madritensis is native to southern and western Europe, but has been introduced and naturalized across nearly the entire world. In North America, it occurs primarily in the western United States, specifically in Oregon, California, and Arizona. It was brought to North America in 1848, and had become naturalized by the 1890s. Within its native range, it grows in cultivated fields and steppes; in North America, it grows in waste areas, road verges, and disturbed areas. In both its native and introduced ranges, it grows primarily on dry stony or sandy soil. In California, this weedy grass occurs in areas disturbed by wildfires. It grows from sea level up to elevations of 1,300 m (4,300 ft).
