Kansas Thistle

Prickly Nightshade

Solanum rostratum

Buffalobur weeds in a bean field
Buffalobur weeds in a bean field. Photo courtesy of Howard F. Schwartz. Licensed under CC BY 3.0.
Buffalobur is an aggressive bush-like annual weed that is covered in sharp spikes and is toxic to animals. It prefers dry soils but will grow in all kinds of cultivated soil. A single plant can produce 7500 seeds which it distributes by turning into a tumbleweed.