Description: This introduced perennial grass is 2½–3½' tall and usually unbranched. The culms are dull green, hairless or slightly pubescent, and terete. The blades of the alternate leaves are up to 10" and 2/3" across; they are greyish blue on the upper side, green on the lower side, hairless, and flat. The leaf blades are ascending to spreading and somewhat floppy in habit. The leaf sheaths are greyish blue, hairless, and closed, although they usually split open near the ligules.
Each culm
terminates in a panicle of floral spikelets up to 8" long; the entire panicle
has a tendency to lean sideways or droop from the weight of the spikelets. The
branchlets of this panicle are ascending to spreading during the period of
bloom, otherwise they are more erect and contracted. The branchlets occur in
whorls along the central stalk of the inflorescence, and they often divide into
secondary branchlets. These branchlets are green, hairless, and somewhat wiry.
Each elongated spikelet is about ¾–1¼" in length; it
consists of a pair of glumes and 5-10 fertile lemmas that are arranged in 2
columnar ranks. During the period of bloom, the spikelets are whitish green,
sometimes with purplish or reddish tints. The glumes are about 1/5" (5 mm.) to
1/4" (6 mm.) in length; they are narrowly lanceolate, hairless, and shorter
than the lemmas. The individual lemmas are about 1/3" (8 mm.) to 1/2" (12 mm.)
in length; they are narrowly lanceolate, hairless, and usually awnless. On rare
occasions, some plants may have lemmas with awns up to 2 mm. in length. The
outer surface of each lemma has several longitudinal veins. The blooming period
occurs during early to mid-summer. Shortly afterwards, the spikelets and culms
become light tan. The elongated grains are about 1/3" long and light tan or
brown. The root system is fibrous and produces abundant rhizomes. Dense
colonies of plants are often formed.
Cultivation: This robust grass prefers mesic
conditions, full or partial sun, and a fertile loam or clay-loam. It can spread
aggressively.
Range &
Habitat: Smooth Brome is a common grass that occurs in every county
of Illinois (see
Distribution
Map). It was introduced as a pasture or forage grass from Eurasia. Habitats
include pastures, fallow fields, grassy areas along roads, degraded meadows,
little-mowed areas of city parks, and waste areas. So far, Smooth Brome has not
invaded prairies and other native ecosystems to any significant degree.
However, this could change in the future as this species appears to be more
common with each passing year.
Faunal
Associations: An introduced insect from Europe, Athysanus
argentarius (Silver Leafhopper), is often found in fields containing Smooth
Brome. Other insects that feed on Bromus spp. (Brome Grasses) include
Melanoplus femurrubrum (Red-Legged Grasshopper), Mermiria
bivittata (Two-Striped Slantfaced Grasshopper), Phoetaliotes
nebrascensis (Large-Headed Grasshopper), and the moth Leucania
multilinea (Many-Lined Wainscot). The seeds of Brome grasses are attractive
to upland gamebirds and some sparrows. Their foliage is eaten by rabbits and
hoofed herbivores, including elk, deer, and livestock. Unlike other Brome
Grasses, the spikelets of Smooth Brome lack awns that can injure the mouthparts
and gastrointestinal tract of hoofed herbivores. Dense colonies of Smooth Brome
provide cover for small rodents, and it is possible that they eat both the
seeds and foliage.
Photographic
Location: A grassy area near the lake at Kaufman Park in Champaign,
Illinois.
Comments: The majority of
Bromus spp. (Brome Grasses) have been introduced from Eurasia (either
deliberately or accidentally). Many of these species are weedy and aggressive,
and Smooth Brome is no exception. It can be distinguished from other Brome
Grasses by the absence of awns on its spikelets (rarely with awns up to 2 mm.
long); almost all other Brome Grasses in Illinois have spikelets with
conspicuous awns (greater than 2 mm. long). An exception is Bromus
catharticus (Rescue Grass), which has been collected only once in Champaign
County, Illinois. Rescue Grass is occasionally planted in the southern states
as a source of winter forage. It is an annual grass with leaf blades up to
¼" across. In contrast, Smooth Brome is a perennial grass with leaf
blades greater than ¼" across. Another common name of Bromus
inermis is Hungarian Brome.