Puncturevine

Tribulus terrestris

Family: Zygophyllaceae

Other Common Names: caltrop, goathead, cat's-head, devil's thorn, tackweed
Weed class: B
Year Listed: 1988
Native to: Africa, Asia, Australia and Europe
Is this Weed Toxic?:

livestock

Why Is It a Noxious Weed?

Puncturevine is a toxic plant and a serious weed in pastures, roadsides, waste places and cultivated fields. The spines of the fruit can cause damage to animals and people. It's sharp spines can puncture bicycle tires and shoes. While typically not grazed, puncturevine is toxic to livestock, especially sheep, when consumed in quantity. It’s also a painful problem to the fruit pickers when growing in orchards or vineyards.

How would I identify it?

General Description

Puncturevine is a summer annual herb growing flat along the ground, from a simple, woody taproot. The fruit is a woody burr with sharp, rigid spines (strong enough to puncture bicycle tires or penetrate shoe soles).

Flower Description

The small, yellow flowers are borne on short stalks at leaf nodes. Flowers are solitary and have 5 petals, 5 sepals and 10 stamens.

Leaf description

Leaves are opposite, oblong and have short stalks. They are 1 to 3 inches long, hairy, and pinnately compound (having leaflets). Each leaflet is 1/4 inch long.

Stem description

Stems are numerous, hairy, and up to 6 feet long. They form a dense mat.

Fruit Seed Description

The fruit is a woody burr with sharp, rigid spines. Burrs break apart into 5 sections, which some say each resemble a goat's head.

Where does it grow?

Puncturevine is found in pastures, roadsides, waste places, parks, agricultural areas. Please click here to see a county level distribution map of puncturevine in Washington.

How Does it Reproduce?

Puncturevine reproduces by seed, which typically germinate from April to October, depending on conditions. Seeds commonly germinate after rainfall or irrigation. Seed production per plant typically ranges from 200 to 5,000 seeds or in some conditions up to as many as 100,000.

How Do I Control It?

General Control Strategy

Puncturevine spreads by seed so controlling plants prior to seed production is critical to prevent further seed entering the seedbank. When working in puncturevine infestations, make sure to clean shoes, clothing and tires to prevent spreading seeds to other areas. Use any of these, or a combination of these methods to control puncturevine. After puncturevine control, plant areas with site appropriate plants to provide competition and reduce further puncturevine invasion.

Mechanical Control

Puncturevine can be hand-pulled or controlled by hoeing or digging up, ideally prior to seed formation in the spring. If plants have already produced seeds, make sure to remove all possible spiny burrs from the ground. Make sure to wear gloves when removing puncturevine and be careful of the sharp spines. Shallow tilling, 1 inch or less, can also be used on small plants in the spring to control the plant prior to flower and seed development. Tilling deeper in the soil may just bury that will survive longer. All methods will need to be repeated as new seeds germinate during the year and for at least four years due to seed viability. Continue to monitor and control as needed. Mowing is ineffective due to the plant’s low growth form.

Biological Control

The puncturevine seed weevil, Microlarinus lareynii, and the puncturevine stem weevil, Microlarinus lypriformis are two biocontrol agents that have been researched and approved for the biological control of puncturevine. Unfortunately, these biocontrol agents do not provide effective control in Washington State. For more information about the biological control of puncturevine and other noxious weeds, please visit WSU Extension Integrated Weed Control Project.

Herbicide Control

Appropriate herbicide use can provide effective control of puncturevine. After the plants have emerged from the soil, and before the plants develop seeds, postemergent products are effective. The smaller or younger the plant, the better the postemergent herbicides work. Make sure to treat plants before they develop seeds. When choosing a soil applied chemical for puncturevine control, consider whether a selective or non-selective product is needed. Always read the label instructions before applying any herbicides for proper rate and timing. Use chemicals that are compatible with your goals. Please refer to the PNW Weed Management Handbook and contact your county noxious weed coordinator for site specific recommendations.