Plants cespitose, tussock forming. Culms 10-60 cm; basal sheaths brown. Leaves: bladeless sheaths 1-3 per culm, expanding distally, to 1 mm wide; blades filiform, trigonous, not more than 1 cm. Inflorescences: involucral bracts absent. Spikelets solitary, erect, globose-subglobose to ovoid-oblong, 10-20 mm in flower, to 50 mm in fruit; scales lead-colored to greenish gray with white-hyaline margins to 1 mm wide; empty scales more than 10, ovate-lanceolate; proximal scales reflexed or spreading at maturity, 5-10 mm. Flowers: perianth bristles 10 or more, white, seldom reddish or brown, 10-18 mm, smooth; anthers 1-3 mm. Achenes ovoid to obovoid, 1.9-3.5 mm, apex minutely apiculate. 2n = 58, 60.
Perennial herb with rhizomes, densely tufted 10 cm - 0.7 m tall Leaves: basal, to 1 cm long and 1 mm wide, thread-like, three-angled, with a sheathing base that encloses the stem. Bladeless sheaths one to three per culm, expanding near the tip, to 1 mm wide, mostly growing below the middle of the culm. 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 (rarely reddish or brown), more or less straight, elongated, 1 - 2 cm long, much longer than the achene. Stamens exserted. Anthers 1 - 3 mm long. Pistil one. Style three-cleft. Fruit: a one-seeded achene, 2 - 3.5 mm long, slightly more than half as long as wide, egg-shaped or reverse egg-shaped with a tiny point at the apex, three-angled. Seed with a thin, non-adherent wall. Culm: 10 cm - 0.7 m long, solid, with brown basal sheaths. Spikelets: solitary, upright, 1 - 2 cm long in flower, to 5 cm long in fruit, nearly spherical to spherical to oblong egg-shaped. Floral scales spirally arranged, grayish to greenish gray with whitish margins. The lower scales sterile, ten to fifteen, blackish with whitish margins, 0.5 - 1 cm long, narrowly egg-shaped with a long-pointed tip, becoming reflexed or spreading at maturity.
Similar species: The distinguishing characteristic of this species is its solitary spikelets. The other Eriophorum species of the region bear spikelets in groups of two or more.
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). Vaginatum means "with a sheath."
Very densely cespitose, forming large tussocks; stems 2-7 dm; lvs clustered at base, with filiform blade 1 mm wide; 1 or 2 dilated, bladeless sheaths mostly below
the middle of the stem; spike solitary; basal sterile scales 10-15, lance-ovate, blackish, long-acuminate, with white or pale margins, spreading or reflexed at maturity; bristles white or seldom brownish or reddish; anthers 2-3 mm; achene distinctly obovate, 2.5-3.5 mm, slightly over half as wide, minutely (0.1-0.2 mm) apiculate; 2n=58, 60. Bogs and open conifer-swamps; circumboreal, s. to N.J., Pa., and n. Ind., and Alta. Fr Apr.-July. (E. callithrix, misapplied) Our plants are var. spissum (Fernald) B. Boivin. (E. spissum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.