Solanum rostratum is a species of nightshade (genus Solanum) that is native to the United States and northern and central Mexico. Common names include buffalobur nightshade, buffalo-bur, spiny nightshade, Colorado bur, Kansas thistle, bad woman, Mexican thistle, and Texas thistle.

It is an annual, self-compatible herb that forms a tumbleweed. Individual plants reach 1–1.5 m (3.3–4.9 ft) tall, have once or twice pinnatified leaves(see image of leaf), and abundant spines on the stems and leaves.

It produces yellow flowers with pentagonal corollas 2–3.5 cm (0.79–1.38 in) in diameter and weakly bilaterally symmetric (see flower-closeup image). In its native range S. rostratum is pollinated by medium- to large-sized bees including bumblebees.

Solanum rostratum flowers exhibit heteranthery, i.e. they bear two sets of anthers of unequal size, possibly distinct colouration, and divergence in ecological function between pollination and feeding.

The fruit, a berry, is enclosed by a prickly calyx. The seeds are released when the berries dry and dehisce (split apart) while still attached to the plant.

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