4. Eriophorum tenellum Nuttall, Gen. N. Amer. Pl. 2: additions. 1818.
Plants colonial fron long-creeping rhizomes. Culms (10–)20–90 cm × 0.5–0.8(–1.5) mm, scabrous distally. Leaves: blades trigonous-channeled in cross section, to 45 cm × 1–1.5(–3) mm; distal leaf blade 3–25 cm × 1–1.5 mm, longer than its (1–)2.5–9 cm sheath. Inflorescences: blade-bearing involucral bracts solitary, similar to distal leaf, blade sometimes brown proximally, 0.8–6 cm. Spikelets (1–)2–7, in subumbels, ovoid, 7–10 mm in flower, 20–30 mm in fruit; peduncles 5–20(–60) mm, scabrous; scales green to red-brown to almost black, sometimes with green center, ovate-elliptic, 3–4.5 mm, scarious, margins narrow, to 0.2 mm, midrib prominent, fading distally or proximal scale with 2–4 thinner or equally prominent lateral ribs, apex obtuse. Flowers: perianth bristles 10 or more, cream, 10–20 mm, smooth; anthers 1–2 mm. Achenes narrowly obovoid, 2.5–3 mm.
Fruiting summer. Bogs and wet, peaty substrates; 0–500 m; St. Pierre and Miquelon; N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que.; Conn., Maine, Mass., Mich., N.H., N.J., N.Y., Pa., R.I., Vt.