Resembling no. 9 [Equisetum arvense L.], but much more robust; sterile stems 5-30 dm, 0.5-2 cm thick, with more numerous (commonly 20-40) but lower ridges, their sheaths mostly 1-2.5 cm, with slender, attenuate teeth 3-8 mm, the branches 4-6-angled, fertile stems 2.5-6 dm, 1-2.5 cm thick, their sheaths 2-5 cm, with 20-30 prominent teeth connate in groups of 2-4; cone 4-10 cm. Moist low places; Europe and N. Afr.; Alaska panhandle to s. Calif.; formerly (but perhaps not now) in n. Mich. The Amer. pls have been segregated as var. braunii (Milde) Milde.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.