Grass family (Poaceae)
This perennial grass forms a dense tuft of basal leaves spanning up to
8" across and 6" tall. The blades of these leaves are 2-6" (5-15 cm.)
long and 0.5–2.5 mm. across; they are green to bluish green, linear in
shape, rather stiff, and rough-textured along their margins.
Occasionally, one or more flowering culms develop that are 1-2' tall.
The culms are green (immature) or light tan (mature),
terete, hairless, and erect to stiffly ascending. Each culm has
about 2 alternate leaves along the lower one-half of its length. The
blades of alternate leaves are similar to the basal leaves, except
smaller in size; they are erect or stiffly ascending along the culms.
The sheaths of these leaves are green, longitudinally veined, and
rather tight. At the junction of each sheath and blade of the alternate
leaves, there is a sparse tuft of white hairs. The nodes along the
culms are slightly swollen.
Each culm terminates in 1-3 floral spikes; these spikes are
either horizontal or ascending, and they
are about 0.75–2" (2–5 cm.) long. Each spike has a rachilla
(stalklet) from which 2 rows of floral spikelets hang below. The
rachilla of each spike is sparsely hairy and either green, purplish
green, or reddish purple; it is straight to slightly curved downward in
the middle while it is immature, becoming light tan and more curved as
it becomes mature. The rachilla extends beyond the adjacent floral
spikelets by 1-6 mm., forming a short spike-like tip. The junction of
the rachilla with the culm is hairless (or nearly so). The narrow
floral spikelets are 5-7 mm. long and adjacent to each other.
Immature spikelets are reddish purple, white, or light green, while
mature spikelets are light tan. Each spikelet consists of a pair of
glumes, a fertile lemma, and 1-2 aborted sterile lemmas. One glume is
1.5–3 mm. long, while the other glume is 3.5–6 mm. long; both
glumes are linear-lanceolate in shape, slightly convex along their
outer surfaces, and either smooth, slightly rough-textured, or hairy
along their midveins. Between the glumes, there is a fertile lemma
about 3.5–6 mm. long; this lemma is linear-lanceolate in shape,
short-awned (1-3 mm. long), and hairy at its base. The sterile lemma(s)
is 1-3 mm. long, occurring on a short stalk; it is hairy at its base
and 3-awned (each awn is 1-3 mm. long). The florets of the fertile
lemmas bloom intermittently during the summer for about 2-4 weeks; they
are cross-pollinated by the wind. The anthers of the florets are
yellow, while their feathery stigmas are white. At maturity, with the
exception of the persistent glumes, the spikelets detach from the
rachilla. The grains are 2.5–5 mm. long, narrowly ellipsoid in shape,
and flattened along one side. They are blown about by the wind to a
limited extent. The root system is fibrous and abundantly branched,
extending into the ground up to 6 ft. deep. The foliage of this grass
dies down during the winter.
preference is full
sun, dry-mesic to dry conditions, and sterile soil containing clay,
gravel, or sand. Strongly acidic soil is not tolerated. Drought
tolerance is excellent, but competition from taller plants is limited.
Northern ecotypes of this grass are very winter-hardy; it is also
tolerates high summer temperatures. Because of the C4 metabolism of
this grass, most growth and development occurs during warm summer
weather. This grass spreads slowly, forming dense tufts of leaves when
it isn't crowded. Under crowded conditions, it will form a sod that is
suitable for grassy lawns in sunny areas.
Habitat: Blue Grama (Bouteloua
gracilis) is regarded as a native plant
in NW Illinois, while in the rest of the state it is adventive.
Overall, it is rare within the state, occurring in widely scattered
counties. The primary range of this grass occurs
in the short-grass prairie of the Great Plains. In Illinois, there are
only small remnant populations. Habitats include sandy hill prairies,
loess hill prairies, gravel hill prairies, sand prairies, gravelly
areas along railroads, and mined land. In Illinois, this grass occurs
in both high quality natural areas and disturbed areas where exposed
barren ground is dry and sunny.
Associations: The larvae of two skippers, Hesperia leonardus (Leonard's
Skipper) and Hesperia
ottoe (Ottoe's Skipper), have been observed to
feed on this grass (Robinson et al., 2010). In addition, a
mealybug that is found in the Great Plains (although not Illinois),
feeds at the base of its culms (ScaleNet, 2014). A large number
of grasshoppers feed on both the foliage and inflorescences of this
grass (see Grasshopper Table).
This includes such species as
Ageneotettix deorum (White-whiskered
(Velvet-striped Grasshopper), Hippiscus ocelote (Wrinkled
Grasshopper), and Trachyrhachys
Grasshopper). Most of
these observations have occurred in the Great Plains region. Among
vertebrate animals, this grass is a major source of food for the
American Bison in the short-grass prairie. Other animals, such as Mule
Deer, rabbits, and rodents, reportedly feed on either the foliage or
seeds, but these observations have occurred in the Great Plains region
and areas further to the west. The awns of the floral spikelets may
cling to the fur of passing mammals or the feathers of birds, spreading
the seeds of this grass to new areas.
A wildflower garden in Urbana, Illinois.
Blue Grama (Bouteloua
gracilis) is an attractive grass, especially
during the summer when it is actively growing and producing its
inflorescences. The floral spikes are very distinctive and at times
rather colorful, superficially resembling short brushes or bushy
eyebrows. In Illinois, it is difficult to confuse Blue Grama with any
other grass, with the exception of the closely related Hairy Grama
This latter grass has hairier floral spikes; both
its rachilla (stalklet) and floral spikelets are more hairy in
appearance than those of Blue Grama. The junction of its rachilla and
its culm is also quite hairy, and Hairy Grama usually produces red
anthers, rather than yellow. This latter grass is native to western and
northern Illinois, where it prefers sandy habitats that are sunny and