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.
Many annual grasses can be confused with
Bromus tectorum. For the annual Bromes (
Bromus), Montana has 7 species
and only 3 are described below. A technical manual for identification is recommended, such as
Manual of Montana Vascular Plants (Lesica et al. 2022).
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.
Ventenata –
Ventenata dubia, non-native, undesirable, Noxious
* Growth Form: Winter annual bunchgrass. Mature plants green to tawny brown.
* Leaves (mature): Narrow, folded lengthwise (inrolled), glabrous to puberulent,
and ascending. At the seedling stage, leaves are narrow and more needle-like when compared to Cheatgrass and Japanese Brome.
* Ligule: Long, membranous, 1-8 mm, and matched above by a purple-black node.
* Inflorescence & Stem: open, airy, pyramidal-shaped, upright panicle that emerges (May-June) while stems harden.
* Callus: Bearded (hairy)
* Glumes: 7-nerved
and smooth.
* Lemmas: Dimorphic. Lowest lemma with straight, persistent awn. Upper lemmas with a bifid tip and a twisted, bent awn (June-July), 1-1.6 cm long that disarticulates with the floret.
* Caryopsis: Seeds (from upper florets) retain bent, twisted awn after dispersal.
