Annual bunchgrass. Stems 20–60 cm. Leaves: blades 2–4 mm wide. Inflorescence an open panicle 10–20 cm long, the branches drooping to one side and at least some flexuous, each branch bearing several spikelets. Spikelets 8–13 mm long, with 5 to 11 florets. Lemmas broad; awn 2–6 mm long, straight to curved downward at maturity (Lavin in
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
See
video on Identifying Invasive Annual Grasses in Montana.
Montana has 7 species of annual Bromes (
Bromus), and only 3 are described below. A technical manual is recommended, such as
Manual of Montana Vascular Plants (Lesica et al. 2012).
Japanese Brome –
Bromus japonicus, exotic and undesirable
* Plants tend to grow in more moist sites than does Cheatgrass (but can co-occur).
* Awns are straight or curved outward, less than 10 mm long.
* Glumes and awns are not usually hairy
* 1st Glume is 3-to 5-veined.
* Spikelets often several at branch ends, not purple-tinged, and with close together lemmas that cover the rachilla
and* Anthers 1-1.5 mm long
and* Lower leaf sheaths are usually densely pilose.
Ripgut Brome -
Bromus diandrus, exotic and undesirable
* Lemmas taper into 2 narrow teeth: bodies are 20-35 mm long and awns are greater than 10 mm.
* 1st Glume is 1-veined.
Cheatgrass –
Bromus tectorum, exotic, undesirable, and State-Regulated
* Seedlings have very hairy blades and sheaths.
* Awns are reddish-purple at maturity and easily stick to clothing and fur, and can get into the nostrils and eyes of animals.
* Glumes and lemmas are usually hairy. 1st Glume is 1-veined.
* Lemmas taper into 2 narrow teeth: bodies are 9-12 mm long and awns are greater than 10 mm.
Field Brome -
Bromus arvensis, exotic, undesirable, and NOT documented in Montana
* Spikelets purplish-tinged
and* Anthers 2.5-5 mm long
and* Lower leaf sheaths with soft appressed hairs.
Rye Brome -
Bromus secalinus, exotic and undesirable
* Spikelets twisted, not purplish-tinged, and with distinct lemmas separated enough to expose the rachilla
and* Anthers 1-2 mm long
and* Lower leaf sheaths glabrous or loosely pubescent and glabrate.
Roadsides, pastures, overgrazed sagebrush steppe, sites with strongly fluctuating water levels, and other open disturbed dry sites (Lavin in
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
