Carex prairea (Prairie Sedge)

Plant Info
Also known as:
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; wet calcareous soils; meadows, fens, marshes, swales, shores, conifer swamps
Fruiting season:June - July
Plant height:12 to 40 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Spikes: Flower shape: indistinct Cluster type: panicle Cluster type: spike

[photo of flowering spikes] Several to numerous small spikes, all essentially alike, stalkless or nearly so, erect to ascending, not usually crowded at the tip of the stem, the lower separated ¼ to 1 inch from each other, the group of spikes (inflorescence) straight to arching and 1 to 3½ inches long, the lowest often branched with up to 10 spikes on the branch. Spikes mostly have a few staminate (male) flowers at the tip and pistillate (female) flowers below (androgynous) but occasionally are all staminate or all pistillate or nearly so. At the base of a lateral spike is an awned, scale-like bract, the lowest as long as or somewhat longer than the attending spike but much shorter than the inflorescence.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of stem leaf sheaths] Leaves are basal and alternate with 3 to 5 leaves on the lower ¼ of the stem, 1 to 3 mm wide, up to 20 inches long but not usually overtopping the flowering stems. Stem leaf sheaths tightly wrap the stem and are more or less solid copper-colored, especially at the tip, otherwise greenish dotted coppery red, straight to slightly concave or convex across the top, and the tip of the sheath extending 2 to 8 mm above the leaf base. The ligule (membrane where the leaf joins the sheath) is usually much longer than wide. Leaves are hairless and rough along the edges, V-shaped in cross-section when young, and erect to arching at the tip.

[photo of basal sheaths] Bases are wrapped in a brown sheath that is not fibrous. Stems are slender, 3-sided, rough textured on the angles, erect to ascending, elongating up to about 3 feet at maturity. Not all plants produce flowering stems. Plants form dense clumps from short rhizomes and may form colonies.

Fruit: Fruit type: seed without plume

[close-up of mature spikes] Fruit develops in late spring through early summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Spikes usually contain a few to several fruits that are appressed to ascending and overlapping on the stalk.

[photo of perigynia front and back, scale and achene] Pistillate scales are broadly lance to egg-shaped, light reddish-brown with whitish edging and a green midrib drying to light brown, tapering to a pointed tip, about as long as and as wide as or wider than the perigynia, and mostly concealing it. Perigynia are 2.5 to 4 mm long, 1.1 to 1.4 mm wide, light to dark brown or yellowish at maturity, convex and strongly 6 to 9-veined on the outer (front) surface with or without a narrow groove down the center of the lower body (formed by the raised veins), flattened and weakly veined on the inner (back) surface, hairless but with minute serrations along the tip edges, firm, leathery and tightly wrapping the achene, the body egg-shaped, straight across to rounded at the base with a short stalk-like appendage (stipe), the tip tapered to a green to light brown beak up to 1.4 mm long with 2 teeth at the tip. Achenes are 1.2 to 2 mm long, .7 to 1 mm wide, flattened lens-shaped, tapering to a stalk-like base, sometimes abruptly so.

Notes:

Carex prairea is a species found across Minnesota in a variety of wet places with calcareous soils, including wet meadows, drainage ditches, shores, prairie swales, and the borders of lakes and streams, and may be the dominant ground cover in some areas.

Carex is a large genus, with over 600 species in North America and 150+ in Minnesota alone. They are grouped into sections, the species in each group having common traits. Carex prairea is in the Heleoglochin section; some of its common traits are: growing in (usually) dense clumps, slender stems 1mm wide or less at the tip, basal sheaths brown, leaves flat or V-shaped in cross-section when young, leaves hairless, sheaths coppery to red dotted, lowest bracts scale-like and awned, numerous spikes often branched, terminal spike usually with staminate flowers at the tip (androgynous), lateral spikes androgynous or all-pistillate, perigynia flattened in cross-section, strongly veined on the front, thick-walled or leathery, abruptly tapered to a stalk-like base (stipe), beaked with 2 teeth at the tip, flattened lens-shaped achenes. Members of the Heleoglochin section somewhat resemble those of the Multiflorae and Vulpinae sections, both of which (usually) lack the copper-colored or red dotted sheaths, and have perigynia that are more spongy and not thick-walled or leathery.

Carex prairea is distinguished from other sedges by the combination of: clump forming, widest leaves 3mm wide or less, stem leaf sheaths solid coppery-red especially at the tip, the tip of the sheath extended 2 to 8mm above the leaf base, most or all spikes with a few staminate flowers at the tip (androgynous), the leathery perigynia 2.5 to 4mm long, distinctly nerved on the front and with a short stipe. It most closely resembles Carex diandra, which has sheaths that are white with coppery and/or white dots and spikes that are more congested, the inflorescence typically straight rather than arching, and the perigynia slightly smaller and more often dark brown. Other species with a somewhat similar inflorescence are Carex siccata, Carex sartwellii, and members of the Divisae section, all of which are rhizomatous and not clump-forming, lack the dotted stem leaf sheaths, and do not have thick-walled or leathery perigynia.

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More photos

Photos courtesy Peter M. Dziuk taken in Pope and Winona counties. Photos courtesy Steve Eggers taken Scott County.

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