Buffalobur nightshade, buffalobur, Kansas thistle, mala mujer

Androcera rostrata (Dunal) Rydberg; Solanum heterandrum Pursh

Herbs, annual, erect, moder­ately to densely armed, to 1 m, prickles yellow, straight, to 12 mm, moderately to densely pubescent, hairs sessile to long-stalked, stellate, 6–10-rayed, central ray equal to or longer than lateral rays. Leaves petiolate; petiole 2–10 cm; blade simple to twice-compound, ovate to elliptic, (2–)4–16 × 3–12 cm, margins lobed to 1–2 times divided with 2–4 main leaflets per side, leaflets with deep, rounded lobes, base truncate to subcordate. Inflorescences extra-axillary, unbranched, 5–12-flowered, 4–11 cm. Pedicels 0.5–1.5 cm in flower, erect and 0.5–1.5 cm in fruit. Flow­ers bilaterally symmetric; calyx accrescent and tightly covering fruit, densely prickly or bristly, 7.5–12.5 mm, densely stellate-pubescent, lobes linear to lanceolate; corolla yellow, rotate-pentagonal, 1.5–3.5 cm diam., with abundant interpetalar tissue; stamens unequal, lowermost much longer and curved; anthers narrow and tapered, dehiscent by terminal pores, short anthers 4, yellow, 6–8 mm, longer anther reddish or purplish, 10–14 mm; ovary glabrous. Berries brown, globose, 1–1.2 cm diam., glabrous, dry, without sclerotic granules. Seeds dark brown, flattened, 2–3 × 1.8–2 mm, minutely pitted and irregularly ridged. 2n = 24.

Flowering year-round. Disturbed sites, versatile in soil tolerance, roadsides, pasturelands; 0–2500 m; B.C., N.B., N.S., Ont., Que.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico.

Solanum rostratum is widespread in the central Mexican highlands from Chihuahua and Coahuila to Puebla and Oaxaca, and its native range likely extends from Mexico City north to the United States Great Plains. It is widely introduced outside this presumed area of origin.

Solanum rostratum is considered a noxious weed in several states. It is often invasive in gardens, pastures, and disturbed areas. The plants are extremely spiny, and there are reports of pigs being poisoned by eating the berries and roots. This species is thought to be the original host of the Colorado potato beetle (Leptinotarsa decemlineata) before potatoes were widely cultivated in the western and central United States. The beetle then adopted potatoes as its primary host and rapidly spread eastward.