Bromus inermis Leyss.

Hungarian Brome, Smooth Brome

Threat Level	Category
Established	Grass

Description

Bromus inermis is a deep-rooted rhizomatous perennial grass with a large flower cluster that droops to one side due to weight. It can form dense clonal colonies.

Height

Bromus inermis grows 1 to 3.5 feet tall (to 1.1m). The culms are light green, hairless to short-pubescent, and usually unbranched, terminating in a panicle inflorescence.

Leaves

Alternating blades are flat, glabrous (smooth), 8-15mm wide, 25-35cm long, and grayish-blue with green underneath.

Flowers

Smooth brome flowers from early to midsummer. The inflorescence is typically 4 to 8 inches (10-20 cm) at anthesis, often drooping to one side from the weight. Usually there are 4-10 hairless, wiry branches from a node, ascending and stiff. Whitish-green spikelets are 15-30 mm long and about 3mm wide with 7 – 11 flowers per spikelet typical. The glumes (5-7 mm) are shorter than the lemmas.

Lemmas are 8-12 mm long with 3 or 5 veins, with the outer pair of veins often inconspicuous, and typically awnless. Rarely a 2 mm awn may be present. Awns typically lacking from the spikelets is one of the most identifying features of this plant. It makes smooth brome a grass that many mammals can eat without damage to their mouth and/or gastrointestinal tract.

After flowering, the spikelets and culms turn light tan in color, and spikelets disarticulate above the glumes.

Images

Photo: Robert Vidéki, Doronicum Kft., Bugwood.org
More images of Bromus inermis

Life History

Habitat

Prefering mesic conditions with full or partial sun, clay-loam or fertile loam soils are ideal for smooth brome. Typically found in areas where the natural vegetation has been degraded from human activity, this grass can spread aggressively to form a monoculture of dense colonies. It can be found on roadsides, grassy meadows, the edge of woodlands, pastures, prairies, pastures, waste areas and infrequently mowed parks and lawns.

Bromus inermis seeds and young shoots are eaten by a variety of animals including insects, birds, rodents and hoofed herbivores. Dense colonies of the grass can also provide habitat for reptiles, rodents and other wildlife.

Origin and Distribution

In the Grass Family (Poaceae), Bromus inermis is native to Eurasia and like many brome grasses was introduced either purposely or on accident as a pasture and forage grass. It is found in most parts of the country but is sparse in the southeast.

Management Recommendations

Chemical Control

The most effective way to remove Bromus inermis from native grasslands is to spray it with glyphosate after a fall killing freeze (27°F or colder for three consecutive hours or more). This is when native warm season grasses have gone dormant and the cool season Bromus inermis is still growing. Apply the treatment within ten days of the killing freeze.

References

Gleason H.A., Ph.D. and Arthur Cronquist, Ph.D. (1991) Manual of Vascular Plants of Northeastern United States and Adjacent Canada (2nd ed.) Bronx, NY: The New York Botanical Garden (p. 772)

Hilty J. (Dec. 9, 2017) Grasses, Sedges, Rushes, & Non-flowering Plants in Illinois, Retrieved from Illinois Wildflowers, n/a, IL: John Hilty

Seirer T., USDA (2012) Smooth Brome Grass - Control in Conservation Reserve Program (CRP) Fields. Retrieved from: NRCS USDA, Kansas City, KS: United States Department of Agriculture

Swearingen, J., C. Bargeron. (2016) Invasive Plant Atlas of the United States. Retrived from Invasive Plant Atlas, Tifton, GA: University of Georgia Center for Invasive Species and Ecosystem Health.