Stems: branches glabrous or glabrescent; branchlets yellow-brown, red-brown, or brownish, usually glabrous, rarely pilose. Leaves: stipules rudimentary to foliaceous on early ones (absent on proximal ones); petiole deeply grooved adaxially, margins covering groove, 4–26 mm, pubescent or puberulent to glabrescent adaxially; largest medial blade oblong, narrowly oblong, narrowly elliptic, elliptic, or lanceolate to obovate, 53–114 × 14–35 mm, 2.7–6.3 times as long as wide, base convex or cuneate, margins flat or slightly revolute, crenate or serrulate, apex acuminate, acute, or ± caudate, abaxial surface glabrous or glabrescent, adaxial dull or slightly glossy, glabrous or glabrescent; proximal blade margins crenate or crenulate; juvenile blade reddish. Catkins: staminate 20–60 × 5.5–10 mm, flowering branchlet 3–17 mm; pistillate moderately to very densely flowered, slender to stout, 20–60 × 5–8 mm, flowering branchlet 5–31 mm; floral bract 1–2.3 mm, apex rounded or acute, abaxially hairy (mainly proximally), hairs wavy. Staminate flowers: abaxial nectary 0.2–1.1 mm, adaxial nectary oblong, square, or ovate, 0.2–0.6 mm, distinct; filaments distinct, hairy on proximal 1/2; anthers ellipsoid. Pistillate flowers: adaxial nectary obovate to square, 0.3–0.5 mm; ovary pyriform, beak gradually tapering to or slightly bulged below styles; ovules 30–36 per ovary; styles distinct 1/2 their lengths, 0.2–0.3 mm; stigmas flat, abaxially non-papillate with rounded tip, 0.1–0.2 mm. Capsules 3–6 mm. 2n = 38 (44), 57, or 88.
