Puncturevine is an annual weed found in dry, sandy areas. Its stems form dense mats that crowd out desirable plants. The stems grow 6 to 8 feet long and may twine up buildings and fences. Both the stems and the oblong leaves are covered with silken hairs, giving the plants a silvery appearance. Small yellow flowers bloom from June to September but open only in the morning on clear days. They are followed by pods of 5 1/4-inch spiny burs that fall to the soil, where they may lie for several years before germinating.
For best results, treat before burs are produced. To prevent seedlings from becoming established, treat the soil before seedlings emerge.