Fire On The Mountain

There has been much confusion in the literature between this and the following species, Euphorbia heterophylla.

Herbs, annual, shrubby, erect to 1 m tall. Stems glabrous, hollow. Leaves alternate; stipules brownish glands; petiole to 1.5 cm, pilose; leaf blade lanceolate in outline, violin-shaped, to 10 × 5 cm, abaxially sparsely pilose, glabrescent, adaxially glabrous, base cuneate, margin shallowly and irregularly toothed, apex obtuse. Inflorescence a terminal cyme forking ca. 4 times, cyathia densely clustered; basal bracts similar to leaves but with a bright orange-red blotch at base, upper bracts progressively smaller, more lanceolate, subsessile, entirely red. Cyathia ca. 3.5 × 3 mm; involucre barrel-shaped, glabrous, lobes ca. 1.5 × 1.5 mm, rounded, margin deeply and bluntly toothed; glands 1(or 2), funnel-shaped, opening transversely elliptic, ca. 2 mm wide. Male flowers: bracteoles ligulate, feathery; stamens ca. 4 mm. Female flower: ovary pedicellate, glabrous; styles ca. 2 mm, bifid almost to base. Fruiting pedicel reflexed to 5.5 mm; capsule deeply 3-lobed, ca. 4 × 5 mm. Seeds ovoid-conical, ca. 2.8 × 2.2 mm, apex acute; seed coat sharply warty, blackish brown. Fl. and fr. May-Nov. 2n = ?56.

Cultivated, sometimes naturalized. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [native to America; naturalized in the Old World].

Euphorbia heterophylla Linnaeus f. cyathophora (Murray) Voss; E. heterophylla var. cyathophora (Murray) Grisebach.

Erect annual herb to 1 m. Leaves: petiole to 1.5 cm; lamina panduriform; margin irregularly toothed; base cuneate; apex obtuse. Inflorescence of densely clustered cyathia in terminal cymes. Basal bracts similar to leaves but with a bright orange-red blotch at the base; upper bracts smaller, more completely red. Involucral gland 1, barrel shaped, with a transversely elliptic opening. Capsule 4 × 5 mm, exserted on a reflexed pedicel. Seeds blackish-brown bearing sharply pointed warts.

Pantropical; introduced in tropical Africa and becoming naturalised

Euphorbia cyathophora, known by various names including dwarf poinsettia, fire-on-the-mountain, and paintedleaf, is native to North and South America and naturalized elsewhere. They belong to the Cyathium type of inflorescence. Here, the inflorescence axis is convex in shape.