Carex media (Intermediate Sedge)
|Also known as:||Close-headed Sedge, Norway Sedge, Scandanavian Sedge|
|Habitat:||part shade, sun; moist, thin, rocky soil; rock pools, talus slopes, wet meadows, shrublands|
|Fruiting season:||June - July|
|Plant height:||6 to 24 inches|
|Wetland Indicator Status:||GP: FACW MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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2 to 5 spikes (typically 3) mostly crowded at the tip of the stem, erect to ascending, short-stalked to stalkless, each up to about ½ inch long, round to oval in outline; the lowest spike is occasionally somewhat farther down the stem and longer stalked. The terminal spike is staminate (male) at the base and pistillate (female) at the tip (gynecandrous); lateral spikes are all-pistillate. At the base of the lowest pistillate spike is a leaf-like bract that may or may not over-top the terminal spike.
Leaves and stems:
Leaves are basal and alternate, mostly near the base, 2 to 4 mm wide, much shorter than the flowering stems. Stem leaf sheaths are membranous on the front side and concave to U-shaped at the tip. Leaves are hairless, V-shaped when young and becoming flat. Bases are wrapped in a sheath that is reddish-brown to reddish-purple at the base and may become fibrous. Stems are erect to ascending, slender, 3-sided, smooth except near the spikes, elongating up to about 24 inches at maturity, and are much longer than the leaves. Plants form loose to dense clumps from short rhizomes.
Fruit develops in late spring through mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes each contain up to 25 fruits that are ascending to widely spreading and crowded on the spike.
Pistillate scales are lance to egg-shaped with a blunt or pointed tip, dark purplish-brown to nearly black including the midrib, sometimes with a narrow white edging around the tip half, awnless, are shorter than and about as wide as the perigynia, and conspicuous against the lighter colored perigynia. Perigynia are 2.1 to 3.5 mm long, hairless, initially very pale green turning golden brown at maturity, nerveless or at most 2 ribs, not much inflated, narrowly elliptic in outline, widest at or above the middle, abruptly tapering to a stalk-like base, tapering to a minute beak, the beak often dark brown to blackish and smooth or occasionally with a few serrations along the edge, the tip usually with 2 small teeth. Achenes are 3-sided in cross-section, widest near the tip.
Carex media is a circumpolar species that, except for disjunct populations in the Driftless area of Wisconsin and Iowa, reaches the southern edge of its range in Minnesota. It is found primarily in thin soils and crevices along the margins of rock pools on the shore of Lake Superior, the Pigeon River and the Kettle River. According to the DNR, its fragile, rocky habitat was once thought safe and largely inaccessible, but a boom in development and recreational activities, particularly along Lake Superior's north shore, has put this species and others like it at risk. Carex media was listed as a MN Special Concern species in 2013 and is currently Endangered in Wisconsin.
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 media is in the Racemosae (formerly Atratae) section; some of its common traits are: loosely to densely clump forming, sometimes rhizomatous, base usually red-purple and often fibrous, leaves hairless and V-shaped in cross-section when young, 1 to 10 spikes, the lowest bract leaf-like or thread-like, spikes round to cylindric in outline, terminal spike usually pistillate at the tip and staminate at the base (gynecandrous), lateral spikes all-pistillate or with a few staminate flowers at the base, pistillate scales dark brown to black and blunt-tipped to awned, perigynia erect to spreading, hairless, somewhat flattened, short-beaked to beakless, the beak sometimes toothed, 3-sided achenes, usually calcareous habitats.
Carex media should not be confused with any other sedge in Minnesota; it is distinguished by the combination of: 2 to 5 spikes (usually 3), terminal spike pistillate at the tip and staminate at the base (gynecandrous), lateral spikes round to short-cylindric and mostly crowding the terminal spike, pistillate scales dark brown to purplish-black including the midrib, perigynia elliptic with a dark, minute beak, perigynia initially very pale green turning golden brown, and usually a rocky habitat. It superficially resembles Carex buxbaumii, which is distinguished by scales with a green midrib and long taper to sharp point at the tip, scales mostly longer than the perigynia, typically found in wetlands and is long-rhizomatous, forming colonies. In some older references Carex media is listed as Carex alpina or a subspecies of Carex norvegica.
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- Intermediate Sedge plant
- Intermediate Sedge habitat
- Intermediate Sedge in a rock crevice
- perigynia turning golden brown
Photos by K. Chayka and Peter M. Dziuk taken along the north shore of Lake Superior in Cook County.
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