Description from Flora of China
Euphorbia epilobiifolia W. T. Wang; E. geniculata Ortega; E. taiwaniana S. S. Ying; Poinsettia geniculata (Ortega) Klotzsch & Garcke var. heterophylla (Linnaeus) Klotzsch & Garcke.
Herbs, annual, erect to 1 m tall, often tinged red. Stem glabrous to sparsely pilose at apex, hollow. Leaves alternate; stipules purplish glands, fairly conspicuous; petiole to 2(-4) cm; leaf blade ovate, to 12 × 6 cm, abaxially pilose especially on midrib and veins, glabrescent, adaxially glabrous to sparsely pilose near margin, base cuneate, margin with minute distant gland-tipped teeth, apex obtuse. Cymes terminal and axillary, each forking ca. 5 times, cyathia densely clustered; basal bracts similar to leaves but paler green, progressively smaller. Cyathia ca. 3.5 × 2.5 mm; involucre barrel-shaped, glabrous; gland ca. 1 mm, funnel-shaped, opening circular, ca. 1.2 mm across, often red-rimmed; lobes ca. 1.3 mm, subcircular, deeply toothed with minutely ciliate margins. Male flowers: bracteoles few, ligulate, feathery; stamens ca. 4 mm. Female flower: ovary pedicellate, glabrous or occasionally minutely puberulent, perianth forming an obvious rim; styles ca. 1 mm, occasionally minutely puberulent, bifid to halfway. Fruiting pedicel reflexed to 6 mm; capsule exserted, ca. 4.5 × 5.5 mm, deeply 3-lobed. Seeds conical, ca. 2.6 × 2.4 mm, apex acute, bluntly warty, blackish brown.
Weed of cultivation and other disturbed areas. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [native to America, now pantropical].