Culms very slender, densely tufted, not stoloniferous, glabrous, 1-5 young shoots developing within the sheaths parallel to the main axis; basal sheaths closed to a third or half length, open above with overlapping margins, mostly pale or drab brown, long-persistent, not becoming fibrous; blades setaceous, 0.3-0.7 mm wide, with 3 large and 0-5 small veins, the sclerenchyma in 3-5+ strands (var. brachyphylla), or forming a ±continuous ring (var. rydbergii); infl 1-10(-13) cm, narrow and spiciform, or somewhat open at anthesis, the first pedicel of the lowermost branches usually no more than 5(-7) mm from the base; spikelets 2-4(5)-fld, the first glume 2-3(-3.5) mm, 1-nerved, the second 2.5-4.5 mm, 3-nerved; lemmas mostly 3.5-5.5(-6) mm, with a short awn 1-3 mm; anthers to ca 2 mm; 2n=28, 42. Widespread in n. N. Amer. and the w. cordillera, s. to Que. and n. Mich., the var. brachyphylla also s. to alpine summits and subalpine cliffs of N. Engl. and N.Y. Two ecotypic, genetically differentiated vars.: Var. brachyphylla, ±alpine, dwarf, 0.5-2 dm, the culms usually less than twice as long as the relatively soft, glabrous basal lvs, which tend to become angular in drying as the soft tissue between the sclerenchymatous ribs collapses; infl 1-4 cm; anthers to 1 mm. Var. rydbergii (St.-Yves) Cronquist, of lower elev., taller, 2-5 dm, the culms mostly 2-3 times as long as the stiff, mostly 1-ribbed, often scabrous basal lvs, which tend to remain rounded in drying; infl 2-10 cm; anthers (1.0-)1.2-1.7(-2) mm. (F. saximontana)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.