Leonard remembers many bicycle flat tires during his youth caused by the appropriately named puncturevine (Tribulus terrestris) fruits. (There was no puncturevine near my Western Pennsylvania home so my bicycle tires never suffered the same fate.) The abundantly produced puncturevine fruits are circular burs that break into tack-like structures at maturity. Each of the five sections is equipped with sharp, sometimes curving, spines and contains 2 to 4 seeds. These burs play havoc with bare feet (and shod feet) and air-filled tires. The burs damage wool, contaminate hay, and are injurious to livestock. The seeds can remain dormant for 5 years and make eradication difficult. It is considered a noxious and invasive weed.
Puncturevine is native to the Mediterranean and has been introduced to temperate latitudes throughout the world. This annual can grow under a wide range of conditions and is especially successful in hot, dry areas. Pastures, cultivated fields, waste and disturbed areas as well as the sides of highways and roads are places to find puncturevine.
Arising from a taproot, puncturevine has a prostrate to somewhat ascending form with trailing stems. It often grows in thick mats. The stems are reddish and, like the leaves, are hairy. The opposite leaves are divided into 4 to 8 pairs of leaflets. The yellow flowers, borne in the leaf axils, have 5 sepals, 5 petals and 10 stamens.
T terrestris has many common names including goathead, Mexican sandbur, tackweed and Texas sandbur. The genus name, Tribulus, is from the Greek “tribeles” or “tribolos” meaning 3-pointed or a caltrop, refering to the shape of the fruits. (A caltrop is an ancient military weapon consisting of an iron ball with projecting spikes strewn on a battlefield to impede cavalry or foot soldiers.) The species designation, terrestris, is “on land” in Latin.
In Eastern Asia puncturevine stems and shoots are eaten. The stems are also used as a thickener. A Web search will find puncturevine extracts for sale to increase testosterone and as an aid in bodybuilding. There is no evidence for its efficacy and puncturevine extracts have not been proven safe.
These puncturevine specimens are growing near the South Elkins Barn in Ash Creek Wildlife Area (Modoc County CA) and were photographed in August and September. Leonard threatened divorce if I brought any plants home to photograph and accidentally got this invasive started on our property.