Plants cespitose or single-stemmed. Culms 20-90 cm × 0.9-1.2 mm distally. Leaves: blades flat, trigonous in cross section distally, to 30 cm × 2-6 mm; distal leaf blade much longer than sheath. Inflorescences: blade-bearing involucral bracts 2-4, sometimes brown-tinged proximally, leaflike, to 7 cm. Spikelets 3-30, in subumbels, lax, oblong-ovoid, 6-10 mm in flower, 15-30 mm in fruit; peduncles (2-)10-60 mm, scabrous; scales dark green to gray, pale proximally, darker distally, ovate to lanceolate, 4-6 mm, margins scarious 0-0.1 mm wide, to 12 weak lateral ribs, midrib prominent, enlarged distally, reaching tip, sometimes excurrent, apex acute. Flowers: perianth bristles 10 or more, white to pale brown, 15-25 mm, smooth; anthers 0.8-2 mm. Achenes dark brown, narrowly obovoid, 2.5-3.5 mm.
Fruiting summer. Marshes, meadows, bogs, fens, wet woods; 0-2000 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask.; Alaska, Colo., Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Mich., Minn., N.H., N.Y., N.Dak., Ohio, Pa., R.I., Vt., Wis., Wyo.
Perennial herb, tufted or with a single culm 20 cm - 1 m tall Leaves: alternate, to 30 cm long, 2 - 6 mm wide, flat, three-angled towards the tip, linear, parallel-veined, with a sheathing base that encloses the stem. The upper leaf blade is much longer than its sheath. Inflorescence: a terminal sub-umbel of three to thirty spikelets, subtended by leaf-like bracts. Bracts two to four, blade-bearing, to 7 cm long. Flowers: minute, subtended by a floral scale, lacking sepals and petals, bearing numerous hair-like bristles that form a dense, cottony tuft when the spikelet reaches maturity. Bristles persistent, white (sometimes brownish), more or less straight, elongated, 1.5 - 2.5 cm long, much longer than the achene. Stamens three, exserted. Anthers 1 - 2 mm long. Pistil one. Style three-cleft. Fruit: a one-seeded achene, dark brown, 2.5 - 3.5 mm long, narrowly reverse lance-shaped, three-angled. Seed with a thin, non-adherent wall. Culm: 20 cm - 1 m long, about 1 mm wide, solid. Spikelets: on 1 - 6 cm long rough stalks, 6 - 10 mm long in flower, 1.5 - 3 cm long in fruit, narrowly egg-shaped. Floral scales spirally arranged, blackish green, darker towards the apex, 4 - 6 mm long, egg-shaped or lance-shaped with a pointed apex, weakly ribbed with a prominent midrib that expands as it reaches the tip.
Similar species: The similar Eriophorum virginicum differs by having colored bristles (which do not elongate until August and September) and a single stamen. Eriophorum angustifolium is also similar but differs by having a reddish tinge on its leaf sheaths and inflorescence bracts.
Flowering: May to August
Habitat and ecology: Rare in the Chicago Region. Found in bogs.
Occurence in the Chicago region: native
Etymology: Eriophorum means "bearing cotton," from the Greek words erion (cotton or wool) and phoros (bearing). Viridicarinatum means green-keeled.
Very much like no. 8 [Eriophorum angustifolium Honck.], but the scales consistently blackish-green, with well developed, notably paler midrib that tends to be expanded distally and reaches the tip of the scale; upper lf-sheath without a dark rim; anthers 0.8-1.5 mm; achenes 2.5-3.5 mm; 2n=58. Swamps, bogs, and wet meadows; Nf. to B.C., s. to Conn., n. O., n. Ind., Minn., Colo., and Wash. Fr May-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.