One of bicyclists greatest enemies is puncturevine (Tribulus terrestris), more commonly known as goatheads. This little plant has caused many a flat tire. They get the name puncturevine because the sharp pointed spikes on the seeds are infamous for puncturing tubes in bicycle tires causing flats. They get the name goatheads because the seeds look very much like a goat's head complete with horns and goatee.
Goathead seeds: picture from: http://plants.usda.gov/java/profile?symbol=TRTEIn it's early stages of development it looks quite harmless. It grows along the ground forming a mat with steams and leaves radiating out from a central point. The leaves are pinnately compound with small leaflets. They have pretty little five petaled yellow flowers. It's not until the flowers bare their fruit that plant becomes dangerous to bicycle tires and bare feet. The fruit seeds or nutlets turn hard, fall from the plant and are then ready to wreak havoc on world. Puncturevine is considered a noxious weed here in Nevada and is problematic in several states throughout the west, including Arizona, California, Oregon and Idaho.
With all the negative hype surrounding puncturevine, most people are oblivious to the more positive qualities that the plant has. It has been used as an aphrodisiac, boosting hormone production in men and women. It has also been used for urinary tract problems, itchy skin and blood purification. In addition, tea made from the steams, leaves and flowers of the plant has been said to be good for arthritis.