This is Puncturevine, also known as Goathead. It's seeds have hard spikes that frequently puncture bike tires and unsuspecting bare feet. It has been declared a "Noxious Weed" by the state or Arizona and our treatments are your best plan of attack to prevent this weed from showing up in your yard!
Excerpts from: Southwest Desert Flora; Tribulus terrestris, Puncturevine
Puncturevine grows up to 10 inches or so and is a low-growing prostrate species. Its stems range from silky to hairy and it has green compound leaves with 6 to 12 leaflets. It also produces yellow flowers, breaking up into 5-nutlets with strong dorsal spines.
In North America, Tribulus terrestris is considered weedy or invasive by 46 states.
Tribulus terrestris is a weedy herb introduced from southern Europe and expanding its range throughout most of North America. Tribulus terrestris is aptly called "Puncture Vine" because its fruits easily puncture bicycle tires and ready inflict pain on unsuspecting humans and perhaps small mammals as well.
Pre-emergent herbicides can help prevent puncturevine outbreaks if you apply before or during the growing season, which is March to October.