Grass family (Poaceae)
Description: This introduced perennial grass is 2½3½' 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 ¾1¼" 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.