Description from Flora of China
Urtica sinuata Blume, Bijdr. Fl. Ned. Ind. 505. 1826; Laportea crenulata Gaudichaud-Beaupré; L. integrifolia C. Y. Wu; L. sinuata (Blume) Miquel; Urtica ardens Blume (1825), not Link (1822); U. crenulata Roxburgh.
Shrubs or small trees, 3-7 m tall; branchlets spreading, semiwoody; bark gray-green; upper stem and branchlets sparsely armed with stinging hairs. Stipules brownish, caducous, ovate-lanceolate, ca. 1.5-2.5 cm, subleathery, puberulent abaxially; petiole 2-10 cm, sparsely pubescent and armed with stinging hairs; leaf blade elliptic, oblong- or obovate-lanceolate, rarely rhombic, 10-45 × 5-20 cm, leathery or papery, penniveined, lateral veins 8-15 each side, anastomosing before margin, prominent abaxially, both surfaces subglabrous or sparsely armed with stinging hairs on veins, base cuneate, rounded, or deeply cordate, margin entire, sinuate to irregularly denticulate, apex acute to long acuminate; cystoliths minutely punctiform, conspicuous adaxially. Male inflorescences in distal axils of branchlets, long paniculate, 5-10 cm; armed with stinging hairs; female inflorescences also in distal axils, 10-20 cm. Male flowers subsessile, in bud 1.2 mm; perianth lobes 4, ovate, pubescent and armed with short stinging hairs; stamens 4; rudimentary ovary obovoid, 0.5 mm. Female flowers: pedicels often fleshy but not swollen; perianth lobes 4, unequal, 1-1.5 mm. Ovary ca. 1.5 mm; stigma ligulate, ca. 2 mm. Achene asymmetrically pyramidal, 5-6 mm, conspicuously verrucose; persistent perianth forming a minute cupule at base. Fl. Sep-Apr, fr. Sep-Nov.
Mixed forests; 300-800 m. S Guangdong, SW Guangxi, Hainan, S Xizang, SW Yunnan [India, Malaysia, Myanmar, Sikkim, Sri Lanka, Thailand].