Buffalo bur, sometimes called Kansas thistle and prickly nightshade, is an taprooted annual weed. It bears long, yellow spines on stems, leaves, and flower heads and can grow up to 2 feet high. Drought resistant, its highest occurrence is in dry, exposed soil. The oblong leaves are 2-3 inches long with deep rounded lobes and are covered with very dense, stiff, and sharp spines. Bright yellow flowers can be seen in summer. In the fall, berries up to 3/8 inch in diameter are enclosed in the dried flower parts and are filled with black, wrinkled, flat pitted seeds.
Control of this plant is important as it is a host for the Colorado potato beetle. When mature, the main stem breaks near the ground and the plant rolls like a tumbleweed, widely scattering the 8500 seeds that each plant produces.
Buffalo bur can be pulled when the soil is moist. Be sure to wear gloves to avoid injury from the spines.
Herbicides should be applied between late bud to early flower. Dicamba, Triclopyr and 2,4-D can be effective in controlling Buffalo bur. Glyphosate in a 2% solution can be applied as a spot treatment.
Photos: Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010