Description: This non-native grass is a spring or fall annual that completes its life cycle within a short period of time (about 6 weeks). It is usually quite small, consisting of a low tuft of vegetation about 4" across and 1½" tall. However, substantially larger plants are sometimes observed. The typical plant has sprawling culms about 2½" long that are unbranched, except at the base. They are light green, glabrous, terete, and largely covered by the sheaths. The blades of the alternate leaves are 1½" long and 1/8" (2.5 mm.) across; they are dull to bright green, hairless, and keel-shaped at their tips. The leaf sheaths are light to medium green, hairless, open, and longitudinally veined. At the junction of each sheath and blade, the ligule consists of a papery membrane.
Each culm terminates in a
flattened panicle of spikelets about ¾" long and ½" across. In
atypical plants, the culms, leaf blades, and panicles are larger in size than
what is indicated above. The somewhat flattened spikelets are light or whitish
green. Each spikelet is about 4.5 mm. long and 2 mm. across; it consists of 2
glumes and 3-6 lemmas that are arranged in two columnar ranks. The curved
glumes are oblong-lanceolate in shape and membranous along their margins; the
larger glume is about 2.0 mm. long, while the smaller glume is about 1.5 mm.
long. The curved lemmas are elliptic-ovate in shape, membranous along their
margins, and faintly veined; sometimes there is a reddish purple patch near the
apex of each lemma. The lemmas are often pubescent along their veins. Unlike
many other Poa spp. (Bluegrasses), there is no web of hairs at the base
of each lemma. The blooming period occurs during the spring or fall. During the
hot weather of summer (or sub-freezing weather of winter), this grass dies down
and becomes tan, dispersing its seeds. The root system is shallow and fibrous.
This grass reproduces primarily by reseeding itself; less often, it may form
rootlets at the nodes of the leaves. Small colonies of plants are formed
occasionally.
Cultivation:
The preference is full sun to light shade, moist conditions, and a loam or
clay-loam soil. This grass often colonizes damp compacted soil that is devoid
of other kinds of vegetation.
Range &
Habitat: Annual Bluegrass is common in most areas of Illinois,
although it hasn't been collected from all counties. It is native to Eurasia.
Habitats include fields and pastures, lawns and gardens, waste ground, and damp
paths in meadows, woodlands, and grassy urban areas. Disturbed areas are
strongly preferred. This grass is more abundant during the spring than the
fall.
Faunal Associations: Because
Annual Bluegrass dies down during the summer, it supports fewer insect species
than other Poa spp. (Bluegrasses). However, some bluegrass feeders that
are active during the spring include the caterpillars of Amblyscirtes
vialis (Common Roadside Skipper), the caterpillars of Poanes hobomok
(Hobomok Skipper), the nymphs of Melanoplus sanguinipes (Migratory
Grasshopper), and both adults and nymphs of Eritettix simplex
(Velvet-Striped Grasshopper). These insects feed on the foliage. Annual
Bluegrass is the preferred host plant of another species, Listronotus
maculicollis (Annual Bluegrass Weevil), whose larvae feed on the roots. The
seeds of Annual Bluegrass and other Bluegrasses are eaten by the Mourning Dove,
English Sparrow, and Field Sparrow. Small mammalian herbivores, like the
Cottontail Rabbit and Meadow Vole, eat both the foliage and
seedheads.
Photographic Location: A
path across a lawn in Urbana, Illinois.
Comments: This dwarf grass is easy to overlook,
particularly when it grows in close proximity to other grasses. For a Poa
sp. (Bluegrass), it has short leaf blades and rather plump-looking
seedheads. It is fairly easy to identify because of its small size and low
sprawling stems. To determine the technical characteristics of this and other
Bluegrasses, it is highly desirable to use a good 10x hand lens. Such lenses
can be used to detect the presence (or absence) of a web of hairs at the base
of a lemma. Some Bluegrasses superficially resemble Eragrostis spp.
(Love Grasses), but the latter have tufts of hair at the junction of the blades
and sheaths. Bluegrasses lack such tufts of hair.