Trichophore nain

Scirpus pumilus Vahl, Enum. Pl. 2: 243. 1805; Baeothryon pumilum (Vahl) Á. Löve & D. Löve; S. alpinus Schleicher ex Gaudin; S. emergens (Norman) Fernald; S. pumilus subsp. rollandii (Fernald) Raymond; S. pumilus var. rollandii (Fernald) Beetle; S. rollandii Fernald; Trichophorum emergens Norman; T. pumilum var. rollandii (Fernald) Hultén

Plants loosely cespitose; rhizomes long, slender. Culms grooved, terete, 5–14 cm, smooth. Leaves: basal sheaths brown; distal leaf sheaths truncate to concave at mouth; blades 2–8.4 × 0.4–0.5 mm, much shorter than culms at flowering and fruiting. Inflorescences: spikelets 3–6-flowered, 3–4.6 × 1.7–2.8 mm; bracts shorter than spikelets, 1.6–2.5 mm, apex mucronate. Spikelets: scales brown, apex obtuse. Flowers: perianth bristles absent; anthers 0.8–1.5 mm. Achenes compressed trigonous to plano-convex, (1.2–)1.4–1.9 × 0.8–1.2 mm.

Fruiting summer (Jul–Aug). Moist to wet coniferous swamps, bogs, riverbanks; calciphile; 20–1500 m [3500 m, Nepal]; Alta., B.C., N.W.T., Que., Sask., Yukon; Alaska, Calif., Mont.; Europe; c Asia.

North American plants have been distinguished as Trichophorum pumilum var. rollandii (Fernald) Beetle; differences from the Eurasian plants are elusive. The chromosome number in Europe is 2n = 78.