Stems all alike, evergreen, mostly unbranched, ±erect, 2-15+ dm, 4-14 mm thick, with mostly 16-50 broad, rounded, roughened ridges; central cavity at least 3/4 the diameter of the stem, much larger than the small vallecular ones; stomates in 2 rows in each furrow; sheaths mostly 5-15 mm, black-banded at the tip and usually also at or near the base, the dark, scarious-margined, basally connate teeth articulate to the sheath but tending to be irregularly subpersistent; cones short-pedunculate, 1-2.5 cm, evidently apiculate. Streambanks and other moist or wet places; circumboreal, s. in Amer. to Fla., Calif., and C. Amer. Amer. pls are var. affine (Engelm.) A. A. Eaton (E. affine; E. prealtum; E. robustum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.