Goathead, Puncturevine

Tribulus terrestris

Zygophyllaceae (Caltrop family)


Goathead is an annual weed in the caltrop family. The prostrate stems radiate from a tap root and bear pairs of opposite leaves. The flattened fruit resembles a goat's head. It breaks into five nutlets, each bearing two strong, woody spines, hence the name puncturevine. The flowers are small and have five yellow petals.


Goathead is an introduced weed from Europe. Widely distributed in disturbed areas and along trails and roadsides, it may abound in severely overgrazed pastures. It is found throughout Texas except on the Gulf Coast and extreme eastern part of the state.

Toxic Agent

The plant causes hepatogenous photosensitization in sheep and possibly also in cattle. All parts of the plant are toxic at all growth stages, but wilted plants are the most hazardous. Goathead also can accumulate high levels of nitrate. The spiny burs this plant produces are mechanically dangerous, producing lesions on the mouth or feet.

Signs of Livestock Ingestion

In natural cases, typical lesions of severe hepatogenous photosensitization were seen, including: Blindness; Peeling of light-colored skin; Loss of lips and ears; High mortality of young animals.

Nitrate poisoning signs also may be evident (see Description of Animal Conditions).