Tribulus, Tribulus terrestris, is also known as Puncture Vine, Caltrop and Goatshead. An important diuretic herb in Ayurvedic and Chinese medicine. Considered an aphrodisiac. Used by bodybuilders as an alternative to anabolic steroids. Apparently improves and prolongs male erection and improves sperm counts. Tribulus is native to Europe, the Mediterranean and Asia. Prefers well drained soils in an open, sunny position. Frost tender and drought resistant. Prostrate annual vine, growing about 1.0m long and about 0.1m high. Small yellow flowers in summer, followed by spiky hard fruit capsules.