Description: This native perennial sedge
is 2½–3½' tall; vegetative shoots are more common than
fertile shoots. The erect culms (central stalks) are unbranched, glabrous,
light green, and triangular in cross-section. On vegetative shoots, there are
6-12 alternate leaves that ascend the entire length of each culm; on fertile
shoots, there are 3-5 alternate leaves that are found along the lower half of
each culm. For both kinds of shoots, the leaf blades are light to medium green,
glabrous, shallowly channeled along their central veins, and rough-textured
along their margins. On vegetative shoots, the blades are up to 25" long and 6
mm. across; they are very long and whip-like. On fertile shoots, the blades are
14" long and 6 mm. across; they are substantially shorter than the blades of
vegetative shoots. Generally, each blade is recurved – ascending at the
base, arching near the middle, and descending toward the tip. The leaf sheaths
are light green, glabrous, and longitudinally veined; they often become loose
toward the bottom of each culm, where a netting of fine veins may persist. Each
ligule is short-membranous, forming a blunt upside-down "V" shape on the culm.
The inflorescence consists of 2-4 pistillate spikelets with their leafy bracts
and 3-5 staminate spikelets. The leafy bracts are up to 12" long and 5 mm.
across, becoming smaller as they ascend the inflorescence. Each pistillate
spikelet is 1¾–2" long and 1/3" across (1 cm.), erect to ascending,
and straight. The lower pistillate spikelets have slender pedicels up to 1"
long that are stiff and straight, while the upper pistillate spikelets are
nearly sessile. Immature pistillate spikelets are light green to yellowish
green, becoming brown with age. The staminate spikelets are up to 1" long and
very narrow; after releasing their pollen, they soon become tan or brown. The
lower staminate spikelets are sessile, while the uppermost staminate spikelet
has a stiff pedicel about ¾" long. The staminate spikelets are above the
pistillate spikelets in each inflorescence. Each pistillate spikelet is densely
crowded with ascending to spreading perigynia and their bracts. The perigynia
are 6-8 mm. long, 3 mm. across, and ovoid-lanceoloid with long slender beaks.
The tip of each beak has a pair of teeth about 1-2 mm. long. The perigynia are
glabrous with numerous longitudinal veins. The pistillate scales are 4-6 mm.
long, lanceolate, and slightly awned; they are membranous, except for their
green/brown central veins.
The blooming period occurs from late
spring to mid-summer; pollination is by agency of the wind. Each perigynium
contains a single achene. The achenes are 2-3 mm. long and about half as much
across; they are ovoid to ellipsoid, 3-angled, and hairless. The root system is
fibrous and long-rhizomatous; large vegetative colonies are often formed from
the rhizomes.
Cultivation: The
preference is full or partial sun, wet to moist conditions, and a fertile loamy
soil, although soil containing rocky or sandy material is also tolerated. This
sedge can spread aggressively.
Range &
Habitat: Plains Slough Sedge is occasional in northern and
west-central Illinois, but uncommon or absent in other areas of the state.
Illinois is located near the eastern range-limit of this species; this sedge is
more common in wetlands of the Northern Plains. Habitats include wet to moist
black soil prairies and dolomite prairies, river-bottom prairies, prairie
swales and sloughs, sedge meadows, openings in floodplain woodlands, swamps,
borders of ponds and rivers, marshes, and roadside ditches. This sedge adapts
to both pristine and degraded habitats if there is sufficient sunlight and
moisture.
Faunal Associations: The
following grasshoppers feed on Carex spp. (sedges) in wetlands:
Stethophyma celita (Otte's Sedge Grasshopper), Stethophyma
gracile (Graceful Sedge Grasshopper), and Stethophyma lineata
(Striped Sedge Grasshopper). Several species of butterflies, skippers, and
moths feed on sedges, especially in wetlands; these species are listed in the Lepidoptera Table.
Waterfowl and some songbirds eat the seeds or seedheads of sedges; the
Bird Table lists many of these
species. Plains Slough Sedge often forms dense colonies of tall plants. This
provides good cover for many kinds of wildlife, including ducks, rails, snakes,
frogs, small rodents, and invertebrates. Some wetland birds also use the culms
and leaves as nesting materials. Deer occasionally use the foliage of this and
similar sedges as "bedding" when they are hiding or resting.
Photographic Location: A prairie swale at
Meadowbrook Park in Urbana, Illinois.
Comments: This sedge is closely related to Carex
trichocarpa (Slough Sedge) and occasionally these two species hybridize.
They are indistinguishable from each other until their inflorescences are
produced – Carex laeviconica (Plains Slough Sedge) has perigynia
that are hairless and shiny, while Slough Sedge has dull-colored perigynia that
are covered with fine hairs. Both of these species prefer similar habitats.
These large sedges are similar to Carex lacustris (Lake Sedge) and
Carex hyalinolepis (Southern Lake Sedge). The latter differ primarily by
having wider leaf blades (up to ¾" across) and they are more stout in
appearance.