Plains black or deadly nightshade

Solanum nigrum Linnaeus [unranked] interius (Rydberg) F. C. Gates

Herbs or shrubs, annual to short-lived perennial, erect, unarmed, to 1 m, sparsely to densely pubescent, hairs unbranched, usually to 1 mm, eglandular. Leaves petiolate; petiole 0.5–3.5 cm; blade simple, ovate to ovate-lanceolate, 4.5–11 × 2.5–7 cm, margins entire to sinuate-dentate, base cune­ate to rounded or slightly decurrent. Inflorescences extra-axillary, unbranched, (2–)3–8-flowered, 2.5–3.5 cm. Pedi­cels spreading in flower, recurved to reflexed in fruit, 0.5–1 cm in flower and fruit. Flowers radially symmetric; calyx not accrescent, unarmed, 2–5 mm, sparsely pubescent, lobes lanceolate, sometimes reflexed in fruit; corolla white, sometimes tinged with purple, with yellowish central star, stellate, 0.5–1 cm diam., without interpetalar tissue; stamens equal; anthers ellipsoidal, 1.8–2.5 mm, dehiscent by terminal pores that open into longitudinal slits; ovary glabrous. Berries shiny purplish black, globose, 1–1.5 cm diam., glabrous, with 2–4 sclerotic granules. Seeds yellowish to brown, flattened, 1.8–2 × 1.5–1.6 mm, finely reticu­late. 2n = 24.

Flowering Jun–Oct. Pastures, open woodlands, stream valleys, thickets, disturbed areas, sandy soils; (100–)500–2500 m; Colo., Idaho, Iowa, Kans., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., S.Dak., Tex., Utah, Wyo.

Solanum interius is endemic to North America and is most common in the Great Plains and eastern Rocky Mountains. Distinctive characters are the basal flower with its pedicel articulated above the base and the very large seeds. In Texas, S. interius can be very difficult to distinguish from S. nigrescens, but S. interius usually has longer calyx lobes. Records of S. interius from Saskatchewan are actually S. emulans.