Carex disperma (Soft-leaf Sedge)
|Also known as:||Two-seeded Sedge|
|Habitat:||part shade, shade; moist to wet; swamps, bogs, alder thickets, along shores|
|Fruiting season:||June - August|
|Plant height:||6 to 24 inches|
|Wetland Indicator Status:||GP: FACW MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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2 to 4 stalkless spikes, occasionally 5 or 6, all essentially the same, the lowest widely separated from the one above it, the uppermost spikes closer together but not overlapping or crowded. At the base of each spike is a scale-like bract, that of the lowest spike is usually longer than the attending spike but not over-topping the terminal spike. All spikes have 1 or 2 staminate (male) flowers at the tip and 1 to 6 pistillate (female) flowers at the base (androgynous).
Leaves and stems:
Leaves are basal and alternate, mostly near the base, .75 to 2 mm wide, up to 12 inches long, shorter than the flowering stems. Stem leaf sheaths tightly wrap the stem and are translucent whitish, straight to shallowly U-shaped at the tip. The ligule (membrane where the leaf joins the sheath) is as long as or shorter than wide. Leaves are flat, hairless, soft, V-shaped in cross-section when young.
Bases are wrapped in a light brown sheath that is not fibrous. Stems are very slender, 3-sided and rough textured, ascending or nodding at the tip, elongating up to 2 feet at maturity and are longer than the leaves. Not all plants produce flowering stems. Plants form loose clumps and may create colonies from slender rhizomes.
Fruit develops in late spring through midsummer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. The empty staminate scales may persist after fruit has dropped off. Pistillate spikes each contain 1 to 6 fruits (typically 2 or 3) that are ascending to spreading and not tightly crowded on the stalk.
Pistillate scales are broadly egg-shaped, translucent white with a green midrib turning tan with maturity, pointed at the tip, and are shorter than and about as wide as the perigynia. Perigynia are 2.25 to 3 mm long, 1.3 to 1.5 mm wide, glossy yellowish to olive green but often turning dark brown to purplish with age, conspicuously many-veined when mature, hairless, thick-walled and hard but spongy at the base, tightly wrapping the achene, oval-elliptic, oval to nearly round in cross-section, rounded at the tip with an abrupt taper to the minute beak. Achenes are 1.5 to 1.75 mm long, up to 1 mm wide, flattened lens-shaped, glossy, yellowish to reddish brown.
Carex disperma is a delicate, circumpolar species found in wet, mossy woodlands and conifer swamps primarily in the northern half of Minnesota.
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 disperma is the lone member of the Dispermae section; some of its common traits are: loosely clump forming, long-rhizomatous, basal sheaths brown, leaves V-shaped in cross-section when young, leaves hairless and 2mm wide or less, 1 to 6 stalkless spikes, spikes all essentially alike with staminate flowers at the tip (androgynous) often with only 1 or 2 staminate flowers, perigynia spreading, oval-oblong, minutely beaked, lens-shaped achenes nearly filling the perigynia, typically growing in forested wetlands.
Carex disperma is distinguished by the combination of: up to 6 spikes that are not crowded, each spike with 1 to 6 perigynia and 1 or 2 staminate flowers at the tip, soft leaves 2 mm wide or less, perigynia oval-elliptic with a minute beak and prominent veins, often turning dark purplish brown. C. disperma superficially resembles a few other sedges: Carex trisperma, which has spikes with staminate flowers at the base (gynecandrous) and the lowest bract over-tops the terminal spike; Carex eburnea, which has long-stalked pistillate spikes and an all-staminate terminal spike; Carex leptalea, which has a single androgynous spike and proportionately narrower, oblong, beakless perigynia.
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- Soft-leaf Sedge plant
- a clump of Soft-leaf Sedge
- a colony of Soft-leaf Sedge
- Carex disperma with Carex leptalea
- perigynia ripened to dark brown
Photos courtesy Peter M. Dziuk taken in Cook and Lake counties.
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