Bromus tectorum (Cheatgrass)

Plant Info
Also known as: Downy Brome, Downy Chess
Genus:Bromus
Family:Poaceae (Grass)
Life cycle:annual
Origin:Europe
Status:
  • Invasive - ERADICATE!
  • Weedy
Habitat:sun; disturbed soil; roadsides, railroads, waste areas, fields
Fruiting season:June - August
Plant height:8 to 30 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: panicle

[photo of panicles] Flowering head is a loose panicle 2 to 8 inches long, nodding to one side, the branches arching, drooping at the tips, the lower branches with up to 8 spikelets (flower clusters) per branch and the upper often with only 1 or 2. Spikelets are stalked, lance-elliptic in outline, not much flattened, 10 to 25+ mm (to 1+ inch) long, with 3 to 8 florets. One or more sterile florets may be at the tip.

[close-up of spikelet] At the base of a spikelet is a pair of bracts (glumes), both hairless to variously hairy and pointed at the tip, the lower glume 6 to 11 mm long and 1-veined, the upper glume 6 to 13 mm long and 3-veined. Surrounding a floret is a pair of bracts (lemma and palea). Lemmas are lance-elliptic, 8 to 13 mm long, usually short-hairy sometimes with scattered long hairs, 5 to 7-veined, notched at the tip forming 2 teeth with a straight awn 10 to 30 mm (to 1+ inch) long arising between the teeth. The palea is shorter than the lemma, elliptic, 2-veined, hairless to sparsely short-hairy on the surface with sparse, long hairs along the veins. Sterile florets are like the fertile but underdeveloped.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath, ligule and node] Leaf blades are spreading to ascending, flat, 2 to 6 inches long, 1 to 6 mm (to ¼ inch) wide, both surfaces densely covered in short, soft hairs and may have a few long, spreading or crinkly hairs. Sheath edges are fused for most of their length (a closed sheath), covered in short, soft hairs and may have a few long hairs near the tip. The ligule (membrane where the leaf joins the sheath) is membranous, 2 to 5 mm long, jagged along the top edge and lacks a fringe of hairs. Nodes are hairy or not. 

[photo of geniculate base] Stems are hairless or hairy just at the nodes, several to many from the base forming clumps, erect to ascending or spreading from the base and rising at a lower node (geniculate). 

Fruit: Fruit type: seed_without_plume

[photo of maturing spikelet] Spikelets frequently turn purple as they mature, the florets eventually drying to light brown, the awns spreading out away from the spikelet as they dry, and each floret dropping off individually leaving the glumes persisting on the stalk.

[photo of mature florets and grain] Grains are somewhat flattened, elliptic, up to 9 mm long, and have a bundle of white hairs at the tip.

Notes:

Bromes are cool season grasses (optimal growth below 75°), usually clump-forming, have closed sheaths, panicles that are often drooping or nodding to one side, multi-flowered spikelets, unequal glumes, and lemmas that are typically awned, hairy and usually notched at the tip forming 2 teeth with the awn arising between the teeth. The longer leaves also frequently twist from near the base so the underside and upperside are flipped. Most Bromes found in Minnesota have sheaths and nodes that are hairy to various degrees and are mostly distinguished by the number of veins on the glumes, length of the lemma awns, and sometimes leaf characteristics.

Cheatgrass, also commonly called Downy Brome, is one of two weedy (and potentially invasive) annual Bromes in Minnesota, the other being Japanese Brome (Bromus japonicus). Besides being an annual, Cheatgrass is distinguished by soft-hairy leaves and sheaths, ligule 2 to 5 mm long, 3 to 8 florets per spikelet, a 1-veined lower glume, 3-veined upper glume, variously hairy lemmas with an awn up to 25 mm long that is spreading at maturity, palea shorter than the lemma and variously hairy with sparse long hairs on the veins. By comparison, Japanese Brome has more florets per spikelet (7 to 15), a (3)5-veined lower glume, 7-veined upper glume, mostly hairless lemmas, the lowest lemma in a spikelet having an awn about half the size of the longest awn (Cheatgrass are all similar), and usually a shorter ligule (1 to 2 mm).

Cheatgrass was introduced to North America in the mid-1800s and has spread across the continent. A winter annual, it produces a dense root mat in early spring, stealing water and soil resources from other spring plants (hence the “cheat”). It invades both high quality and disturbed areas, crowding out native species in natural areas, contaminating agricultural fields, and is especially problematic in the western US. It likes fire and can explode after a burn. A bad plant.

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More photos

Photos by K. Chayka taken in Ramsey County. Photos by Peter M. Dziuk taken in variouls locations around Minnesota.

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