Stem green or red, 80-150 cm tall, stout, often branched. Petiole green or red, 2-6 cm; leaf blade green, red, purple, or yellow, ovate, ovate-rhombic, or lanceolate, 4-10 × 2-7 cm, glabrous, base cuneate, margin entire or undulate, apex obtuse or notched, with a mucro. Flowers in dense clusters at leaf axils or in spike at apex; male and female flowers in same inflorescences. Bracts and bracteoles ovate-lanceolate, 2.5-3 mm, transparent, apex long pointed. Stamens 3. Stigmas 3. Utricles included in perianth, ovate-oblong, 2-2.5 mm, circumscissile. Seeds brownish black, subglobose or obovoid, ca. 1 mm in diam. Fl. May-Aug, fr. Jul-Sep. 2n = 34*, 68, 85*.
Plants annual, glabrous. Stems erect, often branched, 0.8-1.5 m. Leaves: petiole 1/2 as long as blade; blade ovate, elliptic, rhombic, or lanceolate, mostly 4-12 × 1.4-6 cm, base tapering, margins entire, usually undulate, apex acuminate and short-mucronate; distal leaf blades green, red, scarlet, maroon, purple, yellow, and cream (unique to A. tricolor). Inflorescences axillary glomerules. Bracts of pistillate flowers ovate to lanceolate, 5-6 mm. Pistillate flowers: tepals 3, narrowly ovate to lanceolate, 5-6 mm, apex aristate; style branches spreading; stigmas 2-3. Staminate flowers intermixed with pistillate; tepals 3; stamens 3. Utricles ovoid, 2-2.5 mm, rugose, dehiscence regularly circumscissile. Seeds black or brownish black, subglobose, 1 mm diam., shiny.
|Joseph’s coat, summer poinsettia|