Puncturevine  (Tribulus terrestris)

Puncturevine or goathead is a prostrate, summer annual, mat-forming, broadleaf plant with an extensive root system. Listed as a “C-rated*” noxious weed in California, puncturevine produces many burs with sharp spines that can injure humans and animals, as well puncture bicycle tires. In addition, leaves contain compounds called saponins, which can be toxic to livestock (especially sheep) when eaten in quantity. It is prevalent in areas with hot summers, and is found throughout California to about 3300 feet (1000 m). It inhabits agricultural land, especially cotton fields and other disturbed sites.

The stem weevil, Microlarinus lypriformis, and the seed weevil, M. lareynii, are two introduced biological control agents that can keep puncturevine populations in check, but the suppression is cyclic and not always effective.

Habitat

Vineyards, orchards, crop fields, roadsides, railways, walkways, and other disturbed areas. Often found in areas with high soil compaction.

Seedling

Cotyledons (seed leaves) are green above and grayish underneath.  The thick, oblong cotyledons are brittle, have a slightly indented tip, and are creased along the prominent midvein. They are 1/6 to 3/5 of an inch (4–15 mm) long. The first and later leaves resemble those of the mature plant.

Mature plant

Plants grow prostrate over open ground, but when shaded or competing with other plants they can grow nearly erect. Stems occasionally grow over 3 feet (1 m) long, have many branches, are green to reddish brown, and spread radially from the crown. Stems and leaves are covered with hairs. Leaves are mostly 2/17 to 1/5 of an inch (3–5 cm) long, finely divided into three to seven pairs of leaflets, and opposite to one another along the stem.

Flowers

Flowering takes place from March through October. Flowers are bright yellow, about 1/5 to 3/5 of an inch (5–15 mm) in diameter, and are produced singly where the stem and leaf stalk meet. They open only on sunny mornings, except in shady areas.

Fruits

The fruit, a woody five-lobed bur, is gray to yellowish tan, hairy, and roughly 1/5 to 2/5 of an inch (5–10 mm) in diameter. Fruits separate at maturity into five (sometimes four) wedge-shaped nutlets, each with two stout spines and several short prickles. Each nutlet usually encloses three to five seeds

Reproduction

Reproduces by seed.

Related or similar plants

• Puncturvine is unlikely to be confused with other plants.

More information

• Broadleaf ID illustration
• Calflora's distribution map
• For agriculture: UC IPM Pest Management Guidelines
• For gardens and landscapes: UC IPM Puncturevine Pest Note

* A pest of known economic or environmental detriment and, if present in California, it is usually widespread. C-rated organisms are eligible to enter the state as long as the commodities with which they are associated conform to pest cleanliness standards when found in nursery stock shipments. If found in the state, they are subject to regulations designed to retard spread or to suppress at the discretion of the individual county agricultural commissioner. There is no state enforced action other than providing for pest cleanliness.