Blood flower, hierba de la cucaracha, scarlet or tropical milkweed

Subshrubs or herbs. Stems 1–several, erect, sparsely to mod­erately branched, 30–150 cm, minutely pilosulous in a line to glabrate, not glaucous, rhizomes absent. Leaves persistent or gradually caducous from the base, opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge; petiole 4–25 mm, puberulent with curved trichomes in a line to glabrate; blade elliptic or oval to linear, 4–18 × 0.3–4.5 cm, membranous, base cuneate, margins entire, apex acute to acuminate to attenuate, venation eucamptodro­mous to faintly brochidodromous, surfaces sparsely puberulent with curved trichomes on veins abaxially, sparsely puberulent with curved trichomes on veins to glabrate adaxially, margins ciliate, laminar colleters absent. Inflorescences extra-axillary, pedunculate, 5–22-flowered; peduncle 0.5–8 cm, puberulent with curved trichomes in a line, with 1 caducous bract at the base of each pedicel. Pedicels 7–20 mm, puberulent with curved trichomes. Flowers erect; calyx lobes linear-lanceolate, 3–4 mm, apex acute, puberulent with curved trichomes; corolla red, sometimes yellow in throat (to wholly orange or yellow in cultivars), lobes reflexed with spreading tips, elliptic to oval, 6–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 2–2.5 mm; fused anthers yellowish green to tan, cylindric, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments yellow to orange, stipitate, tubular, dorsally somewhat flattened, 3.5–4 mm, exceeding style apex, apex obtuse to acute, glabrous, internal appendage falcate, exserted, arching over style apex, glabrous; style apex shallowly depressed, yellow. Follicles erect on straight pedicels, fusiform, 6–10 × 0.5–1.2 cm, apex acuminate to attenuate, smooth, glabrous. Seeds ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose to smooth; coma 2.5–3 cm. 2n = 22.

Flowering and fruiting year-round. Disturbed areas, fields, orchards, and gardens, canal banks, ditches, streamsides, wet prairies, marshes, swamps, coastal dunes, sandy soils; 0–100 m; introduced; Calif., Fla., La., Tex.; Mexico; West Indies; Central America; South America; introduced also to Old World tropics.

Asclepias curassavica is the only non-native Asclepias species naturalized in the flora area. It is very commonly cultivated, originally for its strikingly colored flowers and their attraction of Lepidoptera and Hymenoptera. Recently, they have been valued also as a host plant for monarch butterflies. Cultivars with pure orange or pure yellow flowers are readily available. The species develops rapidly from seed and can be grown as an annual (in the horticultural sense) anywhere in the region. Though often described as an annual, like all species of Asclepias, it has a perennial habit. It may persist through mild winters at least as far north as Oklahoma but has only become established in frost-free areas of the southern United States.