Plants small to medium-sized. Rhizome creeping, erect, or ascending, blackish brown, nodes and roots with dense long yellowish brown trichomes or glabrous. Aerial stems annual, monomorphic, 10-30(-70) cm tall, 1-2 mm in diam. at middle, much branched; internodes 1.5-6 cm, green but those of lower 1-3 nodes blackish brown, not lustrous. Main stem 4-10-ridged; each side of ridge raised and forming edges reaching lower sheath teeth; each edge with a row of tubercles reaching sheath teeth; sheath tubes long, narrow, grayish green in lower portion, blackish brown in upper portion, with a deep groove going through back of sheath; sheath teeth 5-10, blackish brown, lanceolate, leathery, caudate at apex, persistent. Lateral branches slender, rigid, terete, 4-8-ridged; each side of ridge with edges and tubercles; sheath teeth 4-6, grayish green, deltoid, leathery, persistent. Strobilus terete, 1-9 cm, 4-8 mm in diam., apex blunt; stalk prolonged when mature and 1-3 cm.