Common cocklebur (Xanthium strumariam L.) is a branched, summer annual with distinctive prickly burs in late summer and fall.  Stems are brown to purple spotted and leaves are triangular with a sandpaper texture.  Xanthium species cause liver damage in pigs, and probably dogs, when ingested at 0.75-3.00% of their body weight.  The toxin, carboxyatractyloside, is limited to the seedlings and seeds.  The spiny coats of mature burs can also cause mechanical injury or obstruction of the intestine in livestock.

This weed is found throughout the United States and other temperate areas of the world.  It is particularly troublesome in the southern states and in Mexico.  Common cocklebur is primarily a weed of cultivated and reduced-tillage crops, but can also be found in pastures. Reproduction is by seed and seeds germinate from early spring through summer.  Seeds can germinate as deep as 6 inches below the soil surface.

For more information about identification consult the VT Weed ID Guide or the Univeristy of Missouri Weed ID Guide.

Similar weed species include spiny cocklebur, common burdock, and jimsonweed.

Resource:  Uva, Richard H., Joseph C. Neal, and Joseph M. DiTomaso. Weeds of the Northeast. Ithaca: Comstock Pub. Associates, 1997. Print.