American black or common or West Indian nightshade

Solanum nigrum Linnaeus var. americanum (Miller) O. E. Schulz; S. nigrum var. nodiflorum (Jacquin) A. Gray; S. nodiflorum Jacquin; S. ptychanthum Dunal

Herbs to subshrubs, annual to perennial, erect, unarmed, to 1.5 m, glabrate to moderately pubescent, hairs whitish, unbranched, to 1 mm, eglandular. Leaves petiolate; peti­ole 1–4 cm; blade simple, ovate to ovate-elliptic, 2–10.5 × 1–4.5 cm, margins entire or shallowly sinuate-dentate, base decurrent. Inflorescences extra-axillary or leaf-opposed, unbranched, usually umbel-like, 3–10-flowered, 0.5–3 cm. Pedicels erect or spreading, 0.3–1 cm in flower, to 1.5 cm in fruit. Flowers radially sym­metric; calyx somewhat accrescent, unarmed, 1–3 mm, lobes deltate, strongly reflexed in fruit; corolla white, sometimes with yellowish central star, stellate, 0.4–0.8 cm diam., without interpetalar tissue; stamens equal; anthers ellipsoidal, 0.7–1.5 mm, dehiscent by terminal pores that open into longitudinal slits; ovary glabrous. Berries shiny purplish black, globose, 0.5–1 cm diam., glabrous, with (0–)2–4(–6) sclerotic granules, usually 2–4 larger and 2 smaller. Seeds pale yellow to brown, 1–1.5 × 0.5–1.5 mm, minutely pitted. 2n = 24.

Flowering May–Nov (year-round in Fla.). Weedy habitats, secondary forest, disturbed areas; 0–1000(–2000) m; B.C.; Ala., Ariz., Calif., Fla., Ga., La., Miss., Mo., Oreg., S.C., Tex., Utah, Wash.; Mexico; West Indies; Central America; South America; introduced in Europe, Asia, Africa, Pacific Islands, Australia.

Solanum americanum is a morphologically variable and globally distributed weedy species. It has often been confused with other species in the black nightshade group such as S. emulans, S. nigrescens, S. nigrum, and S. pseudogracile and has often been referred to as S. nodiflorum in floristic treatments. It is distinguished by its very short anthers and shiny black mature fruits with strongly reflexed calyx lobes and usually two to four (rarely none or as many as six) sclerotic granules per fruit. Leaf shape and pubescence can vary considerably throughout its range, and there are some suspected cases of introgression with other species such as S. nigrescens or S. pseudogracile. The name S. nigrum has been mis­applied to S. americanum (for example, A. E. Radford et al. 1968).