Eriophorum viridicarinatum (Engelm.) Fernald
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Very much like no. 8 [Eriophorum angustifolium Honck.], but the scales consistently blackish-green, with well developed, notably paler midrib that tends to be expanded distally and reaches the tip of the scale; upper lf-sheath without a dark rim; anthers 0.8–1.5 mm; achenes 2.5–3.5 mm; 2n=58. Swamps, bogs, and wet meadows; Nf. to B.C., s. to Conn., n. O., n. Ind., Minn., Colo., and Wash. Fr May–Aug.