[Illustration: Tribulus terrestris]
Common names: PUNCTUREVINE, BURNUT, BULLHEAD, (_TORRITO_)
Arizona, California, and Texas deserts: (_Tribulus terrestris_). Pale
yellow. Summer.
Caltrop family. Size: Prostrate, stems 2 to 6 feet long.
A troublesome annual vine-like weed naturalized from southern Europe,
the Puncturevine has established itself throughout the Southwest below
7,000 feet. Although fairly readily controlled by cultivation, the plant
spreads rapidly in sandy, dry wastelands, often taking over vacant lots
in towns, and areas in the desert where it finds sufficient moisture.
The fruits, which are produced in quantities, are armed with strong
spurs which become embedded in the feet and fur of animals and in
automobile tires. Fruits are also carried by irrigation or flood waters.
Although the spurs are too short to puncture automobile tires, they make
bicycles almost useless in some localities, and are an aggravation to
children who go barefoot—and to dogs.
Flowers and fruits in various stages of maturity may be found on this
fast-growing plant at almost any time during the summer months.
Botanically, Puncturevine is closely related to the Creosotebush and
also to the Arizona-poppy.