This plant is a summer annual that consists of a tuft of flowering
culms and leaves about 2-6" tall. The slender culms are up to 0.5 mm.
across, light to medium green, glabrous, and erect to ascending.
About 1-4 alternate leaves are located toward the bottom of each culm.
The narrow blades of these leaves are ¾-4" long and up to 0.5 mm.
across; they are light to medium green, glabrous, and terete to
flattened. The leaf blades are ascending to widely spreading; their
tips often turn brown in response to dry weather.
Each culm terminates
in an inflorescence consisting of 1-3 spikelets and 1-2 leafy bracts.
The spikelets are up to 3 mm. (1/8") long and a little less across;
they are ovoid to ovoid-globoid in shape and sessile. Each spikelet
consists of numerous perfect florets and their scales, which are
arranged in several tiers. Each floret consists of an ovary with a
divided style and a single stamen; there are neither petals nor sepals.
The outer scale of each floret is 0.5-1.0 mm. in length and elliptic to
obovate in shape, tapering to a narrow point; it has a green central
vein and membranous margins. There is also a hidden inner scale that is
adjacent to the floret; it is about 0.1-0.2 mm. in length and
membranous. Sometimes the inner scale is absent. Immature spikelets are
light green, while mature spikelets are dark brown. There is an erect
leafy bract up to 2" long that resembles an extension of the culm;
there is usually a 2nd lateral bract that is shorter. The blooming
period can occur from mid-summer into the fall. The florets are
wind-pollinated. The florets are replaced by tiny achenes about
0.5 mm. long that are light brown, oblanceoloid in shape, and minutely
reticulated. The achenes are without bristles; they are distributed by
wind and water. The root system consists of a dense tuft of fibrous
roots. This annual plant spreads by reseeding itself.
The preference is full sun, moist conditions, and very sandy soil where
there is sparse ground vegetation.
The native Dwarf Bulrush is uncommon in
half of Illinois, while in the southern half of the state it is rare or
absent (see Distribution
). Because of its small size, this
plant may be more common than official records indicate. Habitats
include sandy banks along rivers, river sandbars, and sandy
shorelines along ponds. Dwarf Bulrush typically establishes itself in
these habitats during the summer after spring floodwaters have
Because of its small size, Dwarf
Bulrush is at best a minor source of food to wildlife. Like the closely
related bulrushes (Scirpus
the small seedheads may be consumed
by ducks, rails, coots, and other shore birds. The tiny seeds can cling
to the feathers and muddy feet of these birds, thereby spreading them
to other wetlands. Some insects are known
to feed on various parts of bulrushes. These species include
), seed bugs (Cymus
), the plant bug
leaf beetles (Donacia
and the larvae of Elachista
and other moths.
A sandbar of the Embarras River at Fox Ridge
State Park in
Coles County, Illinois.
Other scientific names of Dwarf Bulrush are Scirpus micranthus
different authorities don't always agree on the
classification of this plant. Other common names for this plant include
Small-Flowered Rush and Smallflower Halfchaff Sedge. Because of its
diminutive size, it is very easy to overlook. Dwarf Bulrush is very
similar in appearance to another species in its genus, Hemicarpha
(Drummond's Dwarf Bulrush). This latter plant
by having: 1) spikelets with appressed scales, rather than
spreading scales, and 2) scales that are more broad in shape
(obovate-orbicular). Drummond's Dwarf Bulrush has been found only in NE
Illinois, where it is rare. Both of these species differ from other
bulrushes (Scirpus spp.
by having minute internal scales in their spikelets.