Eriophorum russeolum (Russet Cottongrass)

Plant Info
Also known as: Red Cottongrass, Rusty Cotton-grass
Genus:Eriophorum
Family:Cyperaceae (Sedge)
Life cycle:perennial
Origin:native
Habitat:sun; wet; bogs, fens, marshes, wet meadows
Fruiting season:June - August
Plant height:8 to 30 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 spike] A single, erect cluster at the tip of the stem, oval-elliptic in flower becoming hemispheric to round in fruit, ¾ to 1½ inches long at maturity, with numerous flowers spirally arranged. Flowers are perfect (both male and female parts) with 1 to 3 stamens, a 3-parted style, and 10 or more straight, smooth, thread-like bristles surrounding the base.

[photo of lowest, empty scale] Each flower is subtended by a single scale, though the lowest scales (7 or fewer) are typically empty and somewhat larger and more prominently veined than fertile scales. Fertile scales are 4 to 7 mm long, somewhat egg to urn-shaped, widest above or below the middle, blunt to pointed at the tip, brown to purplish to blackish at the base with pale translucent edging and a prominent brown midvein that does not quite reach the scale tip. There are no leaf-like bracts at the base of the cluster.

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

[photo of upper sheath] Leaves are few, alternate, the uppermost 1 or 2 leaves reduced to bladeless sheaths that are loose, inflated towards the tip, and green becoming papery brown.

[photo of lower leaf and stem] Lower leaves are up to 4 inches long, 1 to 2 mm wide, V-shaped to triangular in cross-section; basal sheaths are persistent and brown to purplish. Stems are unbranched, mostly single, erect, weakly 3-sided in cross-section, hairless and smooth. 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 ¾ to 1½ inches long, red-brown to off-white.

[photo of achenes] Achenes (seeds) are 2 to 2.7 mm long, reddish-brown, 3-sided in cross-section, oblong-elliptic to somewhat urn-shaped in outline, usually widest above the middle, with an abrupt taper to a pointed tip and a few short hair-like projections on the tip end.

Notes:

Eriophorum russeolum (formerly Eriophorum chamissonis) is an occasional sedge of open, wet places and reaches the southern tip 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 shape of the achene tip, but those traits are not as immediately obvious.

There are 2 subspecies of E. russeolum: subsp. russeolum, present across Canada and Alaska, has darker rusty-colored bristles, stems up to 30 inches tall, and a moderate to dense covering of hair-like projections on the tip end of the achene; subsp. leiocarpum, present in Minnesota and northern Wisconsin into Canada, has paler, more off-white bristles, stems usually under 14 inches tall, and sparse hairs on the achene. Both of these were previously considered part of the E. chamissonis complex, but more recent research separated them and leaves E. chamissonis in western North America and in Europe into Russia.

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More photos

Photos by Peter M. Dziuk taken in Isanti and Pine counties.

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