Description: This non-native grass is a winter or
spring annual of variable size. On dry barren ground, it is typically
¾–1½' tall, while on moist fertile ground it can become 2-3'
tall. Individual plants are tufted at the base, sending up multiple unbranched
culms. These culms are terete, green, and very finely pubescent (canescent);
they are largely hidden by the sheaths. The blades of the leaves are up to 4"
long and 1/3" (8 mm.) across; they are whitish green and pubescent on both the
upper and lower sides. The sheaths of the leaves are whitish to reddish green,
densely pubescent, and longitudinally veined. Each culm terminates in a panicle
of spikelets about 2-6" long. Both the central stalk (or rachis) and branches
of this panicle are strongly inclined to droop. An immature panicle is barely
exerted from the sheath of the uppermost
leaf, while a mature panicle is
more exerted and more widely spreading. The individual spikelets are about
¾–1½" long (including their awns). They are whitish to
reddish green and frequently shiny in appearance. Each spikelet consists of a
pair of glumes and 5-9 lemmas that are arranged in two ranks. These lemmas are
appressed together in young spikelets, but they become more widely spreading in
older spikelets. The first glume is 5-7 mm. long, linear, and glabrous to
finely pubescent; it has a single prominent vein. The second glume is 8-10 mm.
long, linear, and glabrous to finely pubescent; it has 1-3 prominent veins. The
lemmas are 10-12 mm. long (excluding their awns), linear-lanceolate, and finely
pubescent to hairy (rarely glabrous); they have 5-7 veins that are more
difficult to discern. The slender awns of the lemmas are about 12-16 mm. long
and more or less straight. The blooming period occurs from mid-spring to early
summer. Shortly afterwards, the entire plant becomes light tan. Disarticulation
of the spikelets is above the glumes. Each awned lemma encloses a single grain
that is long and slender. The root system is fibrous. This grass species
spreads by reseeding itself. Colonies of plants are often formed at favorable
sites.
Cultivation: This weedy grass
adapts to a wide range of conditions, although it is typically found at sites
that are dry, barren, and sunny. Sites with sandy or gravelly soil are
particularly preferred. Where the soil is more moist and fertile, this grass
becomes taller and more erect. It can reseed itself
aggressively.
Range & Habitat:
Downy Brome is found in every county of Illinois and is quite common (see
Distribution
Map). It is native to Eurasia. The first specimen of this species was
collected in Illinois during the 1890's. Habitats include barren savannas, sand
prairies, fields, pastures, vacant lots, landfills, areas along railroads,
roadsides, and waste areas. This is a pioneer species that prefers areas with a
history of disturbance.
Faunal
Associations: Several species of grasshoppers (primarily their
nymphs) feed on the foliage of Downy Brome (see
Grasshopper Table).
Among these species, Downy Brome is a preferred host plant for Melanoplus
sanguinipes (Migratory Grasshopper). Another insect, Oulema
melanopus (Cereal Leaf Beetle), also feeds on the foliage. Hoofed mammalian
herbivores will feed on this grass while it is immature during the spring.
However, the awns of the spikelets on mature plants can cause mechanical injury
to their mouthparts and digestive tracts. The leaves, stems, and seeds of this
grass are eaten by the Prairie Vole; the House House (outdoor population) also
eats the seeds. Some upland gamebirds and granivorous songbirds probably eat
the seeds, although information about this in the Midwest is scant. The long
awns of mature spikelets cling readily to the fur of animals and the clothing
of humans, which helps to distribute the seeds into new areas.
Photographic
Location: Along a railroad in Urbana, Illinois.
Comments: Downy Brome develops very quickly during
the spring; it is one of the first grasses to bloom in the state. This
characteristic is useful in the identification of this species. At this time of
year, Downy Brome has a silky inflorescence that is rather attractive. There
are many Bromus spp. (Brome Grasses) in Illinois, both native and
non-native. The native species are often perennials that are found around
woodlands, while the non-native species are usually weedy annuals that are
found in sunny disturbed areas. In addition to its early maturity, Downy Brome
can be distinguished from other Brome grasses by the long awns of its lemmas
(about ½–¾" in length), pubescent sheaths and leaves, and
strongly drooping inflorescence. Other technical characteristics that are
useful in its identification include the length of the lemmas, the pubescence
of the lemmas, and the number of veins in the glumes and lemmas, as described
above.