I've got two flat tires on my mountain bike right now, thanks to Tribulus terrestris, one of the most well-armed members of the plant world. Also known as caltrops, the fruits have stiff, hard spines that are much like spiky weapons of the same name that has been used in war for over 2000 years to disable horses, elephants and barefoot soldiers. Larger versions have been used in modern warfare against wheeled vehicles. These plants are equal to the metal version if you are traveling by bicycle, a fate I've befallen to over a dozen times in my life. Bummer!!
News to me, though, is the long-time medicinal use of the plant to "promote a healthy male libido and support testosterone." I suppose this belief is derived from the Doctrine of Signatures that once guided herbalists, i.e. that whatever body part or desirable characteristic a plant emulates, it would also cure. So, if you're male and you want to be stiff and hard, like the spines of Tribulus terrestris, just drink a little tea of the plant. Unfortunately, clinical trials have not demonstrated any of the supposed benefits.
Goatheads, devil's thorn and puncturevine are just a few of the other names used for this sturdy species. It thrives in desert climates and is also tolerant of extremely disturbed habitats, so is common in urban areas around the world. Although it has spread to every continent, it is believed to have evolved in the Mediterranean region. Around here, you'll find it in parking lots, growing in cracks in the street, along highways, in empty lots and abandoned agricultural fields. A single plant can cover many square yards of land. Though the fruit is onerous, the little yellow flowers that precede them are very pretty.