Plains Slough Sedge
Carex laeviconica
Sedge family (Cyperaceae)

Description: This perennial sedge is 2–3' tall; infertile shoots are more common than fertile shoots. The erect culms (central stems) are unbranched, glabrous, light green, and triangular in cross-section; infertile shoots have shorter culms than fertile shoots. On infertile 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 infertile 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 up to 14" long and 6 mm. across; they are substantially shorter than the blades of infertile 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 of fertile shoots 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. The pistillate spikelets are 1–2" long, about 1/3" (1 cm.) across, 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 " 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 scales. 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. After disarticulation, the inflated perigynia have the capacity to distribute their achenes by floating on water. The achenes are 2-3 mm. long and about one-half as much across; they are ovoid-ellipsoid, 3-angled, and glabrous. The root system is fibrous and long-rhizomatous; large clonal 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, gravelly, or sandy material is also tolerated. This sedge can spread aggressively. Occasional standing water is tolerated.

Range & Habitat: The native Plains Slough Sedge is occasional in northern and west-central Illinois, but uncommon or absent in other areas of the state (see Distribution Map). 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, dolomite prairies, river-bottom prairies, prairie swales and sloughs, sedge meadows, openings in floodplain woodlands, swamps, low areas along 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: Various insects feed on sedges (Carex spp.) in wetlands. These species include sedge grasshoppers (Stethophyma spp.), semi-aquatic leaf beetles (Donacia spp., Plateumaris spp.), billbugs (Sphenophorus spp.), stem-boring larvae of various flies, seed bugs, plant bugs, aphids, and leafhoppers (Cosmotettix spp.). Caterpillars of the butterfly, Satyrodes eurydice (Eyed Brown), feed on these sedges, as do the caterpillars of several skippers (Euphyes spp., Poanes spp.) and various moths (see Lepidoptera Table). Among vertebrate animals, waterfowl, rails, 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 (Hairy-fruited 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 Hairy-fruited 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 " across) and they are more stout in appearance.

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