OregonFlora: Bromus tectorum vs. Bromus inermis

	Bromus tectorum	Bromus inermis
	cheatgrass, downy brome, downy chess	smooth brome
Habit	Plants annual, 5–90 cm tall.	Plants perennial, 50–130 cm; rhizomatous.
Culms	puberulent.	internodes usually glabrous, rarely pubescent; nodes (2)3–5(6), usually glabrous, rarely pubescent.
Leaves	sheaths densely and softly retrorsely pubescent to pilose; upper sheaths sometimes glabrous; blades 1–16 cm × 1–6 mm, softly hairy on both surfaces.	sheaths glabrous, rarely pubescent or pilose; ligules to 3 mm; blades 11–35(42) cm × 5–15 mm; flat, glabrous, rarely pubescent or pilose.
Inflorescences	5–20 × 3–8 cm; open, nodding; branches 1–4 cm, drooping, 1-sided and longer than the spikelets, usually at least 1 branch with 4–8 spikelets.	10–20 × 1–4(7)cm; open; erect; branches ascending or spreading.
Spikelets	10–20 mm, moderately laterally compressed, not densely crowded, 4–8 florets.	20–40 mm, elliptic to lanceolate; terete to slightly laterally compressed; (5)8– 10 florets.
Glumes	villous, pubescent, or glabrous; lower glumes 4–9 mm, 1-veined; upper glumes 7–13 mm, 3–5-veined.	glabrous; lower glumes (4)6–9 mm, 1(3)-veined; upper glumes (5)7–10 mm, 3-veined.
Lemmas	9–12 mm, lanceolate, glabrous or pubescent to pilose, 5–7-veined; tips acuminate; hyaline; bifid, with teeth 0.8–2(3)mm, awned; lemma awns 10–18 mm; straight.	9–13 mm, elliptic to lanceolate, rounded over the back, glabrous and smooth, occasionally scabrous; the basal part of the backs rarely puberulent; margins sometimes sparsely puberulent; tips acute to obtuse; entire; awnless or awned; lemma awns if present 1–2(4)mm; straight.
Anthers	0.5–1 mm.	3.5–6 mm.
2n	=14.	=28, 42, 56.

	Bromus tectorum	Bromus inermis
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	Disturbed areas, sagebrush steppe, degraded grasslands, roadsides. 0–2400 m. BR, BW, Casc, Col, CR, ECas, Lava, Owy, Sisk, WV. CA, ID, NV, WA; throughout North America; worldwide. Exotic. Bromus tectorum is a relatively short grass with drooping inflorescences. Similar B. sterilis and B. diandrus have longer glumes, lemmas, and awns, and spikelets that hang down at a shallower angle than those of B. tectorum. The introduction of B. tectorum to shrub steppe habitats during a time of massive overgrazing in the late 1800s has made restoration of native plant communities difficult or impossible, even where grazing no longer occurs. Fast-growing B. tectorum seedlings outcompete slower growing native grass seedlings for water in drying soils. At maturity, the awns make B. tectorum unpalatable to livestock.	Mesic uplands, stream terraces, valley bottoms, open forests, roadsides, and ditches. 0–2400m. BW, Casc, Col, ECas, Lava, Owy, Sisk, WV. CA, ID, NV, WA; north to AK, east to Newfoundland and NC, south to Mexico; Eurasia. Exotic. Rhizomatous B. inermis is most likely to be confused with two bromes that have been reported from Oregon but have not been confirmed. Bromus riparius has longer lemma awns, and its basal sheaths decay into a reticulate, thatch-like mass. It is an Asian species introduced for forage and recently collected from a roadside seeding in southwestern Oregon. Bromus pumpellianus is similar but has pubescent lemmas, nodes, and leaf blades.
Source	Flora of Oregon, volume 1, page 374 Barbara Wilson, Richard Brainerd, Nick Otting	Flora of Oregon, volume 1, page 371 Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	B. arenarius, B. briziformis, B. catharticus, B. ciliatus, B. commutatus, B. diandrus, B. hordeaceus, B. inermis, B. japonicus, B. laevipes, B. madritensis, B. orcuttianus, B. pacificus, B. rubens, B. secalinus, B. sitchensis, B. squarrosus, B. sterilis, B. suksdorfii, B. vulgaris	B. arenarius, B. briziformis, B. catharticus, B. ciliatus, B. commutatus, B. diandrus, B. hordeaceus, B. japonicus, B. laevipes, B. madritensis, B. orcuttianus, B. pacificus, B. rubens, B. secalinus, B. sitchensis, B. squarrosus, B. sterilis, B. suksdorfii, B. tectorum, B. vulgaris
Synonyms	Bromus tectorum var. glabratus, Bromus tectorum var. nudus, Bromus tectorum var. tectorum	Bromus inermis ssp. inermis
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Bromus inermis

cheatgrass, downy brome, downy chess

smooth brome

Habit

Plants annual, 5–90 cm tall.

Plants perennial, 50–130 cm; rhizomatous.

Culms

puberulent.

internodes usually glabrous, rarely pubescent;

nodes (2)3–5(6), usually glabrous, rarely pubescent.

Leaves

sheaths densely and softly retrorsely pubescent to pilose; upper sheaths sometimes glabrous;

blades 1–16 cm × 1–6 mm, softly hairy on both surfaces.

sheaths glabrous, rarely pubescent or pilose;

ligules to 3 mm;

blades 11–35(42) cm × 5–15 mm; flat, glabrous, rarely pubescent or pilose.

Inflorescences

5–20 × 3–8 cm; open, nodding;

branches 1–4 cm, drooping, 1-sided and longer than the spikelets, usually at least 1 branch with 4–8 spikelets.

10–20 × 1–4(7)cm; open; erect;

branches ascending or spreading.

Spikelets

10–20 mm, moderately laterally compressed, not densely crowded, 4–8 florets.

20–40 mm, elliptic to lanceolate; terete to slightly laterally compressed; (5)8– 10 florets.

Glumes

villous, pubescent, or glabrous;

lower glumes 4–9 mm, 1-veined;

upper glumes 7–13 mm, 3–5-veined.

glabrous;

lower glumes (4)6–9 mm, 1(3)-veined;

upper glumes (5)7–10 mm, 3-veined.

Lemmas

9–12 mm, lanceolate, glabrous or pubescent to pilose, 5–7-veined;

tips acuminate; hyaline; bifid, with teeth 0.8–2(3)mm, awned;

lemma awns 10–18 mm; straight.

9–13 mm, elliptic to lanceolate, rounded over the back, glabrous and smooth, occasionally scabrous; the basal part of the backs rarely puberulent;

margins sometimes sparsely puberulent;

tips acute to obtuse; entire; awnless or awned;

lemma awns if present 1–2(4)mm; straight.

Anthers

0.5–1 mm.

3.5–6 mm.

=14.

=28, 42, 56.

Bromus inermis

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas, sagebrush steppe, degraded grasslands, roadsides. 0–2400 m. BR, BW, Casc, Col, CR, ECas, Lava, Owy, Sisk, WV. CA, ID, NV, WA; throughout North America; worldwide. Exotic.

Bromus tectorum is a relatively short grass with drooping inflorescences. Similar B. sterilis and B. diandrus have longer glumes, lemmas, and awns, and spikelets that hang down at a shallower angle than those of B. tectorum. The introduction of B. tectorum to shrub steppe habitats during a time of massive overgrazing in the late 1800s has made restoration of native plant communities difficult or impossible, even where grazing no longer occurs. Fast-growing B. tectorum seedlings outcompete slower growing native grass seedlings for water in drying soils. At maturity, the awns make B. tectorum unpalatable to livestock.

Mesic uplands, stream terraces, valley bottoms, open forests, roadsides, and ditches. 0–2400m. BW, Casc, Col, ECas, Lava, Owy, Sisk, WV. CA, ID, NV, WA; north to AK, east to Newfoundland and NC, south to Mexico; Eurasia. Exotic.

Rhizomatous B. inermis is most likely to be confused with two bromes that have been reported from Oregon but have not been confirmed. Bromus riparius has longer lemma awns, and its basal sheaths decay into a reticulate, thatch-like mass. It is an Asian species introduced for forage and recently collected from a roadside seeding in southwestern Oregon. Bromus pumpellianus is similar but has pubescent lemmas, nodes, and leaf blades.

Source

Flora of Oregon, volume 1, page 374
Barbara Wilson, Richard Brainerd, Nick Otting

Flora of Oregon, volume 1, page 371
Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa