Buffalobur

What is buffalobur?

Buffalobur is a spiny annual in the nightshade (potato) family. buffalobur identification is about as easy as weed ID gets: straight yellow spines cover nearly everything except the petals, the leaves are deeply lobed, the flowers are bright yellow stars, and the fruit hides inside a prickly bur. Despite nicknames like Kansas thistle and Texas thistle, it is not a thistle.

It is native to the Plains, but it has become an aggressive weed in many eastern and northern states. It crowds out forage in pastures and rangeland, it is poisonous to livestock, and its burs tangle in sheep's wool and lower its value. Its spines also make it miserable to handle in yards and gardens.

Buffalobur identification: what to look for

You will usually notice the spines first. Confirm with the leaves, flowers and burs, and if you are dealing with seedlings, crush a seed leaf to rule out jimsonweed.

• Spines: Straight yellow spines, about 1/8 to 1/2 inch long, on the stems, leaf stalks and leaf veins. Everything but the petals is prickly.
• Leaves: Alternate, 2 to 6 inches long, cut into 5 to 7 deep, rounded lobes. Both surfaces are hairy, with prickles on the main veins.
• Hairs: Stems and leaves carry tiny branched, star-shaped hairs in addition to the spines.
• Flowers: Bright yellow, five-lobed and flat, about an inch across, in small clusters.
• Burs: After flowering, the spiny flower base enlarges and closes around a berry about half an inch across, forming a bur that holds many small seeds.
• Seedlings: The first true leaf is already lobed, and crushed seed leaves have no smell, unlike jimsonweed's.

Where it grows in the United States

USDA PLANTS lists buffalobur as native to the lower 48 states. Washington's noxious weed board traces its home range to the Midwest and Mexico, and a USDA-hosted grazing fact sheet places its origin on the western plains, noting that it has since become an aggressive weed through most eastern and northern states. It is also introduced in Canada.

It is a weed of disturbance and overuse. Look for it in overgrazed pastures, barnyards, fencerows, roadsides, yards and field margins. It handles sandy soils, dry hard ground and rich, moist cultivated soil alike, and it tolerates drought well, which helps it take over where grass has been grazed or worn thin.

Buffalobur look-alikes

A few plants get mixed up with it:

• Jimsonweed (Datura stramonium): A close relative whose seedlings can be confused with buffalobur's. Crush a seed leaf: jimsonweed gives off a foul odor, while buffalobur has no smell, and buffalobur's first true leaf is lobed.
• Silverleaf nightshade (Solanum elaeagnifolium): A deep-rooted perennial with silvery, velvety leaves, scattered prickles, violet to blue flowers and round yellow-to-orange berries that are not enclosed in a bur. Buffalobur is an annual with yellow flowers and spiny burs.

How to get rid of buffalobur

Pulling, digging and mowing: Because buffalobur is an annual, the goal is simple: no plant gets to make burs. Hoe or pull scattered plants before the first flowers open, wearing thick gloves against the spines. For larger patches, mow repeatedly and closely to keep plants from flowering. A long-standing grazing guide recommends cutting plants as soon as blossoms appear and letting them dry before destroying them, so no seed ripens. Rototilling or hoeing also works on young plants.

Cultural control matters most, because the right conditions keep it from coming back.

• Avoid overgrazing; buffalobur moves into pastures where grass has been weakened.
• Keep livestock out of heavily infested pastures until the weed is under control.
• Mow lawns regularly at the right height for your grass so the turf stays dense.
• Pull or hoe plants before they flower, every season.

Herbicides: Washington State University Extension advises spraying while seedlings are still immature and before they flower. In landscape beds and on bare ground, glyphosate can be used, but only as a spot treatment because it kills any plant it touches. In lawns, WSU lists a combination of 2,4-D, MCPP (mecoprop) and dicamba. Use only a product labeled for your site (lawn, bed, pasture or bare ground), and follow the label, which is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Every buffalobur plant starts from seed, so preventing seed is prevention. Check pastures, lots and roadsides in early summer and remove plants before they bloom, and keep at it each year, since seed already in the soil will keep sprouting.

Keep pastures and lawns thick and avoid overgrazing, so seedlings have little bare ground to colonize. In Washington, the plant is under quarantine, so don't sell, share or move plants or seed.

Questions we get about buffalobur

Similar weeds

JimsonweedDatura stramoniumSilverleaf NightshadeSolanum elaeagnifoliumCommon TansyTanacetum vulgare