Description: This adventive annual grass
is ¾–2' tall and unbranched. The erect culm is light green, terete,
and finely pubescent (clearly visible with 10x magnification). Along the lower
half of the culm, there are about 3 alternate leaves. The erect to ascending
leaf blades are 1-6 mm. across and 2-6 cm. long; they are light green, densely
pubescent on both sides, and soft-textured. The leaf sheaths are light green
and densely pubescent. The nodes along each culm are swollen, dark-colored,
finely pubescent. The ligules are short-membranous and insignificant. Each culm
terminates in a compact panicle of 6-12 spikelets about 4-8 cm. in length. The
spikelets are more or less erect on pedicels up to 1 cm. in length; each
spikelet is about 15 mm. long and 4-5 mm. across with a pair of glumes at the
bottom and 2 columnar ranks of 6-12 lemmas above. The glumes are curved,
glabrous, and awnless with about 5 pale green longitudinal veins; on each
spikelet, the 1st glume is about 5 mm. long, while the 2nd glume is about 7 mm.
long. The lemmas are longitudinally curved, glabrous, pale green, with about
5-7 longitudinal veins; they are 7-9 mm. long, while their straight awns are
4-7 mm. long. Enclosed within each lemma, there is a white membranous palea
with a hairy margin that surrounds the developing grain; this palea is about 5
mm. long, longitudinally curved, and linear-oblong in shape. The blooming
period is late spring to mid-summer. The florets of the lemmas are
wind-pollinated. The grains are narrowly oblongoid and up to 5 mm. long. The
root system is shallow and fibrous. This grass reproduces by reseeding itself.
It often forms loose colonies of small erect plants.
Cultivation: This grass prefers full sun in a dry
open area. It is typically found in poor soil containing clay, gravel, and
possibly sand.
Range & Habitat:
Lesser Soft Brome has been collected from Dupage County and the webmaster has
observed this species along a railroad in Champaign County (see
Distribution
Map). This grass is probably more common than these records indicate
because the various Bromus spp. (Brome grasses), particularly those from
Europe, are difficult to identify and their taxonomic history has been
unstable. Look for this grass in such disturbed habitats as roadsides, gravelly
areas along railroads, and sterile waste areas. Lesser Soft Brome appears to be
less invasive than other Brome grasses from Europe, although it could
conceivably invade dry gravel and sand prairies.
Faunal
Associations: Various short-horned grasshoppers eat the foliage of
Bromus spp. (Brome grasses), including Camnula pellucida
(Clear-Winged Grasshopper), Melanoplus packardii (Packard Grasshopper),
and Phoetaliotes nebrascensis (Large-Headed Grasshopper). The
caterpillars of the moth Leucania multilinea (Many-Lined Wainscot) and
Oulema melanopus (Cereal Leaf Beetle) also feed on Brome grasses. Among
vertebrate animals, the Prairie Vole and probably other small rodents eat the
foliage and seeds of various Brome grasses in open areas. Some upland gamebirds
and granivorous songbirds also eat the seeds, but most observations derive from
records in Western states. During the spring, immature Brome grasses are
palatable to hoofed mammalian herbivores, but mature plants are less palatable
because of the awned spikelets, which can irritate the gastrointestinal tract
and mouthparts of these animals.
Photographic
Location: A gravelly area along a railroad in Savoy,
Illinois.
Comments: This European
grass can be identified by its compact erect inflorescence and its
soft-textured pubescent leaves. It is one of several European Bromus
spp. (Brome grasses) that have been introduced into the United States.
Lesser Smooth Brome and other annual Brome grasses usually prefer dry open
areas with a history of disturbance. Many of these grasses are regarded as
weeds, although some species are cultivated as forage plants during the spring.
Lesser Smooth Brome is a subspecies of Soft Brome, Bromus hordeaceus. It
differs from the typical subspecies by its glabrous spikelets, slightly shorter
lemmas, and smaller stature. The typical subspecies, Bromus hordeaceus
hordeaceus (Soft Brome), has pubescent spikelets. In the past, Soft Brome
has been classified as Bromus mollis, while Lesser Smooth Brome was
regarded as the hybrid Bromus × pseudothominei. Another European
species, Bromus racemosus (Bald Brome), is somewhat similar in
appearance, but this species has a panicle of spikelets that is longer and less
compact; furthermore, the branches of its panicle are more likely to droop. A
species from Western North America, Bromus squarrosus (Corn Brome), has
curved awns that spread outward. In contrast, Lesser Smooth Brome has straight
awns.