Carex communis (Fibrous-root Sedge)

Plant Info
Also known as: Colonial Sedge
Family:Cyperaceae (Sedge)
Life cycle:perennial
Habitat:part shade, shade, sun; average to moist sandy or rocky soil; deciduous and mixed forest, cliffs, bluffs, rocky shores
Fruiting season:June
Plant height:8 to 24 inches
Wetland Indicator Status:none
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: spike

[photo of spikes] Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to ¾ inch long at the tip of the stem. Below the staminate spike are 2 or 3 pistillate spikes, each up to about 3/8 inch (1cm) long, the uppermost close to the staminate spike and the lower more widely separated from each other, but never near the base of the stem. Spikes are stalkless or nearly so. At the base of lowest spike is a leaf-like bract that is much longer than the spike and may overtop the terminal spike but usually not. Bracts become smaller as they ascend the stem, the upper more scale-like with a bristly awn.

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

[photo of stem sheath and ligule] Leaves are basal and alternate, mostly near the base, 1.8 to 5 mm wide (the widest 3 to 5 mm), erect to spreading and shorter than the flowering stem. Stem leaf sheaths are U to V-shaped and translucent whitish-green. The ligule (membrane where the leaf joins the sheath) is longer than wide. Leaves are hairless though may be slightly rough.

[photo of red base] Bases are wrapped in a red sheath that is little fibrous if at all. Stems are erect to ascending, slender, 3-sided, and mostly smooth except rough on the upper stem. Stems may elongate up to 24 inches at maturity and remain longer than the leaves. Plants form loose to dense clumps from short rhizomes and may form large colonies.

Fruit: Fruit type: seed without plume

[photo of maturing spikes] Fruit develops in late spring, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Each pistillate spike contains 3 to 10 fruits, the perigynia ascending, overlapping but not crowded on the spike.

[photo of perigynia, scale and maturing achene] Pistillate scales are 2.5 to 4.1 mm long, lance to egg-shaped, pale to dark brown often with whitish edging, usually tapering to a pointed tip or sometimes the midrib extending to a short awn, and are slightly shorter to slightly longer than the perigynia. Perigynia are 2.8 to 3.8 mm long, 1.2 to 2.6 mm wide, fuzzy hairy, 2-ribbed, green at maturity, the body about as long as wide, spherical to somewhat urn-shaped and round in cross-section, the base initially spongy but shriveling to a stalk-like structure (stipe), and abruptly tapering to a straight to slightly bent beak that has 2 small teeth at the tip. Achenes are 1.4 to 2.3 mm long, 1 to 1.4 mm wide, round to slightly urn-shaped in outline, round to weakly 3-sided in cross-section, and mature to light brown.


Carex communis is an infrequent, though sometimes locally abundant, sedge primarily found in rocky forests and shores, and reaches the western edge of its range in eastern 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 communis is in the Acrocystis section (formerly Montanae); some of its common traits are: mostly dry habitat, hairless leaves, basal sheaths typically fibrous, small spikes often tightly clustered, terminal spike staminate, perigynia typically hairy, perigynia with 2 small teeth at the tip of the beak, achenes 3-sided to round in cross-section.

C. communis is distinguished from other members of Acrocystis by the combination of: short rhizomes, red basal sheaths that are not much fibrous if at all, widest leaves 3 to 5 mm, ligule longer than wide, pistillate scales more or less as long as the perigynia, hairy perigynia with a body about as long as wide, abruptly tapering at both ends when mature. By contrast, Carex pensylvanica has long rhizomes, more consistently fibrous basal sheaths, the widest leaves 3mm or less, a ligule wider than long, and flowers and matures earlier in the season than C. communis. Also similar is Carex peckii, which has a short staminate spike often obscured by the pistillate spikes just below it, widest leaves 3.3mm or less, ligule wider than long, pistillate scales about half as long as the perigynia, a very short beak on the perigynia, and also matures earlier in the season.

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More photos

Photos by K. Chayka taken in Cook county. Photos courtesy Peter M. Dziuk taken in Cook and Lake Counties.


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