Bromus inermis Leyss.

Smooth Brome


CC = *
CW = 5
MOC = 55

© SRTurner

Family - Poaceae/Bromeae

Habit - Perennial cool-season (C3) grass, with rhizomes well developed and creeping, forming loose colonies.

Bromus_inermis_base.jpg Plant base and rhizomes.

© SRTurner

Stem - Flowering stems 45-130 cm long, erect or ascending, glabrous or nearly so.

Bromus_inermis_stem.jpg Stem and leaf adaxial.

© SRTurner

Leaves - Leaves 4-6 per stem. Leaf sheaths loosely overlapping, glabrous, closed, the tip strongly concave (V-shaped), without auricles. Leaf blades 9-35 cm long, 8-15 mm wide, glabrous, dull on the undersurface.

Bromus_inermis_leaf2.jpg Leaf abaxial.

© SRTurner

Bromus_inermis_sheath.jpg Leaf sheath.

Sheaths are closed, sometimes compared to a "V-neck sweater."

© SRTurner

Bromus_inermis_ligule.jpg Ligule.

© SRTurner

Inflorescences - Dense to more commonly open panicles with numerous spikelets, the branches strongly ascending at maturity, sometimes somewhat spreading during development, the stalks of the spikelets shorter than to longer than the spikelets.

Bromus_inermis_inflorescence1.jpg Inflorescence.

© SRTurner

Spikelets - Spikelets 15-40 mm long, circular to slightly compressed laterally in cross-section at maturity, with 4-10 florets. Lower glume 4-8 mm long, narrowly elliptic, 1-nerved, glabrous but usually roughened along the midnerve. Upper glume 7-11 mm long, narrowly elliptic, 3-nerved, glabrous but usually roughened along the midnerve. Lemmas 9-12 mm long, elliptic, rounded on the back, the margins not inrolled at maturity, 3-or 5-nerved, glabrous but usually roughened along the nerves and margins, the apical teeth 0.2-0.5 mm long, awnless or the awn 0.5-2.5 mm long, straight or nearly so. Paleas somewhat shorter than the lemmas. Anthers 3.5-6.0 mm long. Fruits 8-9 mm long, circular in cross-section to somewhat flattened or slightly V-shaped, the longitudinal groove narrow and shallow.

Bromus_inermis_spikelets.jpg Spikelets.

© SRTurner

Bromus_inermis_spikelets2.jpg Spikelets.

© SRTurner

Flowering - May - July.

Habitat - Roadsides, pastures, open, disturbed areas. Widely cultivated as forage and for hay.

Origin - Native to Europe.

Lookalikes - Other species of Bromus.

Other info. - This introduced brome is widespread in Missouri, and also throughout most of the U.S. excepting several southern and southeastern states. Like all bromes, it has a closed leaf sheath. The spikelets are long and cylindrical, and have no awns (or at most very short ones). The lower glume is single-nerved and the upper 3-nerved, and the lemmas are glabrous.

Photographs taken near Labadie, Franklin County, MO, 5-12-2023 (SRTurner).