Trees, 4–20 m. Stems: branches flexible to ± brittle at base, yellow to gray-brown, glabrous; branchlets yellow-brown, gray-brown, or red-brown, glabrous. Leaves: stipules absent or rudimentary on early ones, foliaceous or rudimentary on late ones, apex rounded; petiole (margins covering groove, not glandular or with spherical glands distally), 7–21 mm, glabrous or puberulent adaxially; largest medial blade (sometimes amphistomatous), very narrowly elliptic, elliptic, lanceolate, or lorate, 55–130 × 24–37 mm, 2.8–6 times as long as wide, base convex, cuneate, or cordate, margins serrulate, apex acuminate to caudate, abaxial surface glaucous, glabrous, adaxial dull, glabrous or sparsely pubescent along midrib; proximal blade margins entire or shallowly serrulate; juvenile blade glabrous or pubescent abaxially, hairs white and/or ferruginous. Catkins: staminate 23–80 × 5–12 mm, flowering branchlet 3–28 mm; pistillate 41–110(–127 in fruit) × 8–16 mm, flowering branchlet 17–35 mm; floral bract 1.5–2.8 mm, apex acute to rounded, entire or toothed, abaxially sparsely to moderately densely hairy proximally, hairs wavy; pistillate bract deciduous after flowering. Staminate flowers: abaxial nectary 0.2–0.7 mm, adaxial nectary narrowly oblong to square, 0.3–0.8 mm, nectaries distinct; stamens 3–7; filaments hairy on proximal 1/2 or basally; anthers 0.5–0.6 mm. Pistillate flowers: adaxial nectary square, 0.1–0.6 mm; stipe 1.4–3.2 mm; ovary pyriform, beak slightly bulged below styles; ovules 16–18 per ovary; styles 0.2–0.4 mm; stigmas 0.24–0.31–0.4 mm. Capsules 3–7 mm. 2n = 38.