By Gerry Hernandez, UCE Master Gardener
Puncturevine (Tribulus terrestris) is an aptly named summer annual found widely in California. Native to southern Europe, it can grow under a wide range of conditions, but its success is likely due to its ability to thrive in hot and dry conditions where other plants cannot. Its main weedy characteristic, as indicated by its common names of puncturevine or caltrop, is its spiky seedpods. The seeds of puncturevine are enclosed in a hard caltrop-like case that can injure livestock, people, and pets when stepped on and can even puncture bicycle tires. Another common name is “goathead.”
Puncturevine is a summer annual broadleaf weed that generally grows low to the ground forming dense mats 2 to 5 feet in diameter. The stems radiate out from a central point at the taproot. The plant does not root from the stems. Yellow flowers up to 1/2 inch wide with five petals are found in the leaf axils. After the flower is pollinated, a seedpod forms that is a cluster of five flat spiny burrs containing up to five seeds. As the seedpod matures, it turns gray or tan, gets very hard and breaks apart so that the individual spikes, or burrs, can stick into passing animals and tires. These burrs disperse by adhering to tires, shoes and clothing of people, and the fur, feathers, or feet of animals.
Puncturevine germinates in the spring and summer from seeds produced the previous year. Good soil moisture and warm temperatures are needed for germination, but after the plant is established, it can tolerate dry soils due to its rapidly produced deep taproot. The plant may start flowering within 3 weeks of germination and flowering will continue throughout the summer. Seeds may remain viable in the soil for up to five years. Puncturevine plants cannot tolerate freezing temperatures.
A typical puncturevine plant will produce 200 to 5,000 seeds during one growing season. These seeds and those that did not germinate from previous seasons will contribute to the potential weed population the following year.
The primary method of management for puncturevine in the home landscape and garden is removal of seedlings and older plants by hand or hoeing, taking care to also remove any burrs that fall off the plant. Avoid bringing puncturevine into uninfested areas on shoes and the wheels of mowers or carts. Visit cecolusa.ucanr.edu or ipm.ucanr.edu.
Source: University of California Agriculture and Natural Resources.
