Carex disperma (Soft-leaf Sedge)

Plant Info
Also known as: Two-seeded Sedge
Genus:Carex
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Spikes: Cluster type: spike

[photo of spikes] 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: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath and ligule] 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.

[photo of basal sheaths] 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: Fruit type: seed without plume

[photo of mature spikes] 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.

[photo of perigynia, scale and achene] 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.

Notes:

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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More photos

Photos courtesy Peter M. Dziuk taken in Cook and Lake counties.

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