Juncus filiformis L.
Family: Juncaceae
Thread Rush
Juncus filiformis image

Herbs, perennial, 0.2--3.5 dm. Rhizomes widely creeping, sparingly branched, 1.5--2 mm diam., nodes closely set. Culms terete, 1 mm diam. Cataphylls several. Leaves: blade absent. Inflorescences 3--10(--12)-flowered, loosely congested, 1--2 cm; primary bract terete, nearly equaling to much longer than culm. Flowers pedicellate; bracteoles broadly ovate, tepals light brown or green, lanceolate, 2.5--4.2 mm; inner series loosely subtending capsule at maturity, slightly shorter, margins scarious; stamens 6, filaments 0.5--0.9 mm, anthers 0.5--0.7 mm; style 0.2 mm. Capsules tan, 3-locular, nearly globose, 2.5--3  x 1.8--2.1 mm, shorter than perianth. Seeds amber, 0.5--0.6 mm, not tailed. 2n = 40, 70, 80, 84.

Flowering and fruiting summer. Usually sandy, moist or wet soil along stream banks, pools, lakes or in meadow depressions, rarely in bogs, frequently hidden by larger vegetation; 0--3000 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., Nfld. and Labr., N.B., N.S., N.W.T., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Colo., Idaho, Maine, Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., Oreg., Pa., Utah, Vt., Wash., W.Va., Wis., Wyo.; Eurasia; Atlantic Islands (Iceland).

Stems cespitose or in rows on a short or long rhizome, finely striate, without foliage lvs, 1-4 dm to the infl, surmounted by an erect invol lf half to fully as long; basal sheaths pale brown, seldom over 6 cm; infl 1-2 cm, sparingly branched, each primary branch with 1-4 prophyllate fls; sep lanceolate, 2.7-4.3 mm; pet 2.3-4.1 mm, acutish or obtuse; anthers 6, much shorter than the filaments; fr trilocular, 2.4-3.7 mm, obovoid, short-beaked; 2n=40, 70, 80, 84. Sandy shores, bogs, and alpine meadows; circumboreal, s. in our range to the mts. of N. Engl., N.Y., Pa., and W.Va., and to n. Mich. and n. Minn.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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