Puncture vine (Tribulus terrestris) 

With its sharp, thorny burs that poke into tires, paws, and bare feet, puncture vine is painfully familiar to gardeners in much of the country. An annual weed often found in dry areas, it forms a dense, low mat 5 to 15 feet in diameter.

For best control of small infestations, hoe or dig plants before they can set seed, cutting below the crown to prevent regrowth. Once you've removed puncture vine growing in lawns, improve the soil with compost and sow grass seed in bare spots to prevent the weeds from reestablishing.

For chemical control, preemergence herbicides containing trifluralin may be used on some lawn grasses and ornamentals in late winter or early spring. For postemergence control in lawns, use a selective herbicide.