Eriophorum virginicum (Tawny Cottongrass)

Plant Info
Also known as: Tawny Cotton-sedge
Genus:Eriophorum
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; wet, peaty soil; bogs, conifer swamps, wet meadows, swales
Fruiting season:July - September
Plant height:16 to 48 inches
Wetland Indicator Status:GP: OBL 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

Flower: Flower shape: indistinct Cluster type: round Cluster type: spike

[photo of flowering spikes] Two to 10 erect, very short-stalked spike clusters in a compact head at the tip of the stem, the head hemispheric to round in fruit, with numerous flowers spirally arranged on a spike. Flowers are perfect (both male and female parts) with 1 stamen, a 3-parted style, and 10 or more straight, smooth, thread-like bristles surrounding the base.

[photo of bracts] The lowest 2 to 5 spikes each have a leaf-like bract at the base of the stalk; the bracts are of unequal lengths, up to 6 inches long, and erect to reflexed (downward pointing). Each flower is subtended by a single scale, 4 to 5 mm long, lance to egg-shaped, blunt at the tip, brown often with a green center, and 3 prominent veins.

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

[photo of upper leaf and sheath] Leaves are few, alternate, up to 12 inches long, to 4 mm wide, flat at the base, triangular in cross-section towards the tip, the uppermost leaf much longer than the sheath. Sheaths are straight across to concave at the tip, green, firm, and are tight to slightly loose around the stem. Stems are unbranched, single or a few together, erect, weakly 3-sided to round in cross-section, hairless and smooth except just below the flower clusters. Plants form loose colonies from long creeping rhizomes.

Fruit: Fruit type: seed with plume Fruit type: seed without plume

[photo of achene with bristles] The bristles around the base of a flower elongate with maturity, becoming ½ to ¾ inch long, red-brown to off-white, usually brown at the base and rarely all white.

[photo of achenes] Achenes (seeds) are 2.5 to 4 mm long, brown to black, 3-sided in cross-section, narrowly elliptic in outline, usually widest at or above the middle, with an abrupt taper to a short beak at the tip.

Notes:

Eriophorum virginicum is an occasional to common sedge of open, wet bogs and conifer swamps, usually in peaty soils, and reaches the western edge of its range in Minnesota. The Cottongrasses in Minnesota are separated into two groups: those with an erect, hemispheric to round seed head, and those with multiple, distinctly stalked, nodding spikes. The former group includes E. russeolum, E. vaginatum and E. virginicum, which are not difficult to distinguish from each other. Of these three: only E. vaginatum is densely clump-forming, only E. virginicum has multiple spikes with leaf-like bracts, and E. russeolum is neither clump-forming nor does it have leaf-like bracts. There are other, more subtle differences, such as scale color or the shape of the achene tip, but those traits are not as immediately obvious.

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More photos

Photos by K. Chayka taken in Isanti and Lake counties. Photos by Peter M. Dziuk taken in Cook, Isanti, and Lake counties.

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