Bromus tectorum
Bromus arizonicus
cheat brome, cheat grass, downy brome, downy chess, drooping brome
Arizona brome
5-90 cm, erect, slender, puberulent below the panicle.
30-90 cm tall, to 3 mm thick, erect.
usually densely and softly retrorsely pubescent to pilose, upper sheaths sometimes glabrous;
auricles absent;
ligules 2-3 mm, glabrous, obtuse, lacerate;
blades to 16 cm long, 1-6 mm wide, both surfaces softly hairy.
retrorsely pilose, sometimes mostly glabrous, throats sometimes with hairs;
auricles absent;
ligules 1-4 mm, usually glabrous, obtuse, erose;
blades 8-18 cm long, 3-9 mm wide, flat, sparsely pilose on both surfaces or the abaxial surfaces glabrous.
5-20 cm long, 3-8 cm wide, open, lax, drooping distally, usually 1-sided;
branches 1-4 cm, drooping, usually 1-sided and longer than the spikelets, usually at least 1 branch with 4-8 spikelets.
12-25 cm, somewhat contracted or open;
lower branches shorter than 10 cm, 2-3(5) per node, initially erect to ascending, spreading at maturity, with 1-2 spikelets variously distributed.
10-20 mm, usually shorter than the panicle branches, sides parallel or diverging distally, moderately laterally compressed, often purplish-tinged, not densely crowded, with 4-8 florets.
18-25 mm, elliptic to lanceolate, strongly laterally compressed, with 4-8 florets.
villous, pubescent, or glabrous, margins hyaline;
lower glumes 4-9 mm, 1-veined;
upper glumes 7-13 mm, 3-5-veined;
lemmas 9-12 mm, lanceolate, glabrous or pubescent to pilose, 5-7-veined, rounded over the midvein, margins hyaline, often with some hairs longer than those on the backs, apices acuminate, hyaline, bifid, teeth 0.8-2(3) mm;
awns 10-18 mm, straight, arising 1.5 mm or more below the lemma apices;
anthers 0.5-1 mm.
subequal, smooth or scabrous;
lower glumes 8-12.5 mm, 3-veined;
upper glumes 9.5-14 mm, 7-veined, about as long as the lowest lemma;
lemmas 9.5-14 mm, lanceolate, laterally compressed, prominently 7-veined, strongly keeled at least distally, glabrous or pubescent distally or throughout, marginal hairs, if present, longer than those elsewhere, apices entire or with acute teeth shorter than 1 mm;
awns 6-13 mm, sometimes slightly geniculate;
anthers 0.4-0.5 mm.
= 14.
= 84.
Bromus tectorum
Bromus arizonicus
Bromus tectorum is a European species that is well established in the Flora region and other parts of the world. It grows in disturbed sites, such as overgrazed rangelands, fields, sand dunes, road verges, and waste places. In the southwestern United States, Bromus tectorum is considered a good source of spring feed for cattle, at least until the awns mature. It is highly competitive and dominates rapidly after fire, especially in sagebrush areas. The resulting dense, fine fuels permanently shorten the fire-return interval, further hindering reestablishment of native species. It now dominates large areas of the sagebrush ecosystem of the western Flora region.
Specimens with glabrous spikelets have been called Bromus tectorum f. nudus (Klett & Richt.) H. St. John. They occur throughout the range of the species, and are not known to have any other distinguishing characteristics. For this reason, they are not given formal recognition in this treatment.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Bromus arizonicus grows in dry, open areas and disturbed ground of the southwest, usually below 2000 m. Its range extends from California and southern Nevada into Arizona, New Mexico, and northern Mexico.
Stebbins et al. (1944) demonstrated that, like Bromus carinatus var. carinatus, B. arizonicus obtained three of its genomes from B. catharticus or a close relative, but the remaining three genomes are not homologous with those in B. carinatus, probably being derived from a species in a section other than Ceratochloa. The small anthers of B. arizonicus strongly suggest that most seed is produced by selfing.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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