Buffalobur-Nightshade Family

Beaked nightshade, Colorado bur, Kansas thistle, Mexican thistle, prickly nightshade, sandbur, Texas thistle.

Solanum rostratum

Charactristics. This native to the Great Plains now occurs commonly from the Midwest to the West Coast. It is a drought resistant species that is most commonly found in sandy soil but can grow in a wide variety of conditions. It is primarily found in fields, overgrazed pastures, yards, roadsides, and waste areas. Buffalobur reproduces by seeds that are enclosed within a spiny pod that readily adheres to animal fur and clothing thus enhancing its spread. These seed pods are toxic when consumed and the large spines can cause injury to eyes, nostrils and other soft parts of the body. Although not a highly competitive species it is also problematic as it is an alternate host to the Colorado potato beetle.

Identifying Characteristics. Buffalobur is a low growing, yellow-flowered, spined, hairy annual. The stems (mostly branching in the upper part), are erect and bushy, 1/2 to two feet long. The entire plant, except the for the flower petals, is covered by straight yellow spines, 1/8 to 1/2 inch long. The leaves are alternate and two to six inches long including the stalks. Each leaf is irregularly cut into five to seven lobes, and often these are two to five lobed. The leaves are covered by short yellow star-like hairs, and the midribs, veins, and leaf stalks are spiny. The yellow flowers are five-lobed, wheel-shaped, 1 to 1.5 inches across, in few flowered clusters on spiny flower stalks. The calyx is covered by spines; it enlarges and forms a spiny bur, enclosing and completely covering the seedpod. The seeds are almost circular, 1/2 inch or slightly more in diameter, brown to reddish brown, flattened, irregularly angled, with a finely pitted surface. To identify buffalobur, look for the tomato-like yellow flowers and the unique, extremely prickly leaves, stems and fruits.

Images courtesy of Dr. Fred Fishel, University of Missouri, System Board of Curator.

The relatively large 5 lobed yellow flowers develop early in the summers and typically remain until fall.

Image courtesy of Dr. Fred Fishel, University of Missouri, System Board of Curator.

Economic Importance:  Buffalobur is considered to be a "nuisance weed" of barnyards, corrals, etc. The burs may cause damage and considerable loss in wool value in sheep. Buffalobur is considered noxious on farms and rangelands.

Geographical Distribution:  Buffalobur is native to the Midwest, where it is known to be highly aggressive and invasive. It is widely distributed in the western United States and is common on disturbed sites and sandy soils. There have been frequent repetitive introductions in central and eastern Washington, but buffalobur has never become established. That buffalobur has never established in Washington is due to aggressive control measures taken against the plant rather than its lack of ability to survive in Washington.

Habitat:  Buffalobur grows in fields, overgrazed pastures, yards, roadsides, waste areas, and  barn yards. Although it is adapted to sandy soils, it will also grow on dry hard soils to rich moist soils of cultivated fields.

History:  Buffalobur is a native North American species; its range extending from central Mexico northward across the Great Plains of the United States. It is widely introduced elsewhere, including the U.S.S.R. and Australia. Repeatedly introduced into the pacific northwest, buffalobur usually appears in gardens, where it was planted with flower or vegetable seeds. Land managers found it near Penticton, British Columbia, following reseeding of rangeland. Occasionally, plants sold as tomato seedlings have matured into buffalobur. The name "buffalobur" dates back to the time of settlement of the Great Plains when the plant grew abundantly in the disturbed soil of buffalo wallows. Buffalo carried the burs great distances in their shaggy coats.

Growth and Development:  Buffalobur is an annual species. The plants bloom in late June to early August and the seeds mature from July to Octobe. It reproduces by seeds only.

Response to Herbicides:  2,4-D plus Banvel can control buffalobur: Buffalobur is moderately susceptible to 2,4-D when seedlings are immature. It becomes very resistant to 2,4-D after flowering. A combination of 2,4-D plus Banvel usually provides more complete control than either herbicide alone. Apply 2 quarts 2,4-D (3.8 pound acid equivalent per gallon) plus 1 pint Banvel per acre before plants bloom. Always follow label instructions.

Although buffalobur can be found in some row crops as a weed, it is not considered to be a highly competitive in a row crop situation. However, it is considered a nuisance in waist areas, rangeland, pastures, and yards. Although buffalobur leaves and immature fruit are considered toxic, the spines generally make the plant unpalatable. It should be controlled in a pasture situation to make sure that the plant does not find its way into hay. Buffalobur is ranked as a noxious weed in several states. It is not considered one of Indiana’s problematic weeds. I have only had one call about its control. If you should have buffalobur and wish to control it, cultivation, hand pulling, and repeated mowing have suppressed or controlled it. Using growth regulator herbicides work well in controlling buffalobur. A mixture of 2,4-D and dicamba have been reported to do an excellent job in grass pastures and yards.