Puncture Vine
Tribulus terrestris
Puncture Vine is an obnoxious weed whose seeds are incredibly painful to step on, they easilly puncture your bicycle tires, and sometimes have to be pulled out of your pets' paws. It is a taprooted herbaceous perennial plant that grows as a summer annual in colder climates. They are usually prostrate, forming flat patches, though they may grow more upwards in shade or among taller plants. The leaves are pinnately compound with leaflets less than a quarter-inch long. The flowers are 4-10 mm wide, with five lemon-yellow petals. A week after each flower blooms, it is followed by a fruit that easily falls apart into four or five single-seeded nutlets. The nutlets or "seeds" are hard and bear two sharp spines, 10 mm long and 4-6 mm broad point-to-point.
Caltrop, Yellow Vine, Goathead