Tribulus terrestris is an annual plant in the caltrop family (Zygophyllaceae) widely distributed around the world. It is adapted to grow in dry climate locations in which few other plants can survive. The stems radiate from the crown to a diameter of about 10 cm (3.9 in) to over 1 m (3 ft 3 in), often branching. They are usually prostrate, forming flat patches, though they may grow more upwards in shade or among taller plants.