P&PDL Picture of the Week for
December 6, 2004


Glenn Nice, Weed Diagnostician, Botany & Plant Pathology Department , Purdue University

Although the buffalo may not roam the Great Plains anymore, buffalobur (Solanum rostratum) is still widely distributed.  If you should come across this member of the potato family, a word of advice, don’t grab it.  If you should grab it, you will be rewarded for your bravery by receiving a hand full of spines.

Buffalobur, otherwise referred to as Kansas thistle, Texas thistle, or Colorado bur, is a well armed annual that blooms from May to October (Stubbendieck et al. 2003).  Related to horsenettle (Solanum carolinense) its flower has some similarities.  Buffalobur flowers have five yellow petals that are fused giving the appearance of being a solid skirt with irregular margins (Figure 1).  Its flowers are about 1 inch across.  Leaves are alternate and ovate to elliptic (Figure 2 and 3.) with deep round lobes.  The most notable feather about this plant is that it is fortified with yellow spines everywhere on the plant.  The spines are even found on the fruit, making the fruit look like some kind of medieval weapon (Figure 4).

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.

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 (Banvel, Clarity, etc) have been reported to do an excellent job.

Click image to enlarge

Figure 1. An ant spending some time on a buffalobur flower

Figure 2.  Elliptic and ovate leaf shapes (Ciba-Geigy Corporation)

Figure 3. Buffalobur leaf

Figure 4. Buffalobur fruit showing spines

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service