Bristly nightshade

Solanum heterodoxum Dunal var. setigeroides Whalen, Wrightia 5: 237. 1976

Herbs, annual, spreading, branching from near base, densely armed, 0.3–0.7 m, prickles straight, 4–8 mm, 30+ per cm of stem, sparsely pubescent, hairs ca. 0.2 mm, stipitate-glandular, abaxial leaf surfaces also with scattered, sessile, 4–6-rayed, stellate hairs, central ray equal to lateral rays. Leaves petiolate; petiole 2–7 cm; blade simple to compound, broadly ovate to deltate, 4–11 × 4–8 cm, margins twice-lobed to twice-divided with 2–3 main leaflets per side, leaflets with obtuse or rounded lobes, base truncate. Inflorescences extra-axillary, unbranched, 5–9-flowered, 4–10 cm. Pedicels 1–2 cm in flower, erect and 1–2 cm in fruit. Flowers bilaterally symmetric; calyx accrescent and tightly covering fruit, densely prickly, 4.5–6.5 mm, sparsely glandular-pubescent, lobes lanceolate; corolla violet or blue, pentagonal, 1–1.5 cm diam., with abundant interpetalar tissue; stamens unequal, lowermost much longer and curved; anthers narrow and tapered, dehis­cent by terminal pores, short anthers 2–4 mm, longer anther 3.5–5 mm; ovary glabrous. Berries brown, glo­bose, 1–1.2 cm diam., glabrous, dry, without sclerotic granules. Seeds dark brown, flattened, 2.5–3 × 2–2.5 mm, minutely pitted and weakly ridged or faceted.

Flowering Jun–Oct. Silty, sandy, or gravelly soils, playas, dunes, streambeds, arroyos, open hillsides; 600–2000 m; Ariz., N.Mex., Tex.; Mexico (Chihuahua).

Solanum setigeroides is a weed of disturbed and over­grazed places ranging from central Arizona and New Mexico to extreme western Texas.