Aerial stems dimorphic; vegetative stems green, branched, 30--100(--200) cm; hollow center 2/3--3/4 stem diam. Sheaths squarish in face view, 7--18 × 5--13 mm; teeth green proximally and dark distally, 14--30(--36), 3--12 mm. Branches in regular whorls, ascending to spreading, solid; ridges 4--5, furrowed; valleys rounded; 1st internode of each branch shorter than subtending stem sheath; sheath teeth attenuate. Fertile stems brown, lacking stomates, unbranched, shorter (17--45 cm) than vegetative stems, with larger (15--40 mm) sheaths, fleshy, ephemeral.

Cones maturing in early spring. Coastal marshes, stream banks, ditches, and other wet places; 0--1000 m; B.C.; Alaska, Calif., Oreg., Wash.

Equisetum telmateia subsp. telmateia , from Europe, northern Africa, and the Middle East, differs primarily in having main aerial stem with white internodes, lacking both green tissue and stomates but having green, whorled branches.