Puncturevine (aka Goathead)

Tribulus terrestris¹

Family - Zygophyllaceae¹

Other Common Names - caltrop, cat's-head, devil's thorn, tackweed, puncture weed, Mexican sandbur, Texas sandbur, bullhead.¹ ²

History

Puncturevine is native to the Mediterranean region.³ It was an accidental introduction to the United States, possibly on the wool of sheep imported from Mediterranean Europe. This weed was recognized as problematic as early as 1912 in California, although ranchers reported sightings of it decades prior.⁴ During the first half of the 1900s, puncturevine was one of the most problematic roadside weeds in the U.S., as its burs easily punctured the tires of early cars.³ Puncturevine became such a widespread weed because of its ability to grow in dry and disturbed soils, the large number of seeds it produces, and the ability of the seeds to attach themselves to people, animals, and vehicle tires—thus spreading to new locations.⁴

Noxious Weed Status for Surrounding States:

Idaho - Yes   Washington - Yes   Oregon - Yes    Nevada - Yes    Utah -Yes    Wyoming - No   Montana - No

Reason for Noxious Status

Puncturevine contains several saponin toxins which may lead to photosensitization in sheep when consumed in quantity. After it’s eaten, the substances enter the blood stream and are carried to skin cells, sensitizing them to sunlight, particularly at the lips, ears, and around the eyes, followed by swelling of the head. It has also been shown to cause liver damage to ruminants.² The spines of the fruit can cause damage to animals and people. It's sharp spines can puncture bicycle tires and shoes. It’s also a painful problem to the fruit pickers when growing in orchards or vineyards.¹

Quick Identification

General - Stems are green to reddish-brown, have small hairs, radiate from a central point (where it roots), and may extend ten feet. Although normally prostrate, puncturevine may grow almost upright when surrounded by other plants. The leaves appears on opposite sides of the stem and are divided into five to eight pairs of little leaflets (that also have small hairs). They have small, yellow flowers with five petals, sprouting from where the leaf connects to the stem. Fruits consist of five wedge shaped segments or burs, each with two short spines and numerous smaller prickles.²

Common Look Alikes - Puncturevine resembles spotted spurge (Euphorbia maculata), common purslane (Portulaca oleracea) and common stork’s weed (Erodium cicutarium). The main difference can be seen as: spotted spurge has a milky sap when damaged and its leaves are generally reddish purple on the undersides with a purple spot on top, common purslane has much fleshier leaves (like a succulent), and common stork’s weed has toothed leaves (as opposed to a simple oval) and has purple instead of yellow flowers. Puncturevine is unique with its spined burs, so if you find the spiked seed pods, it is almost definitely puncturevine.⁵ ⁶

Further Physical Description

Flower - The yellow flowers are 1/3 to 1/2 inch wide and borne on short stalks at leaf nodes.¹ ² Flowers are solitary and have 5 petals, 5 sepals and 10 stamens.¹

Leaf - Cotyledon leaves (first leaves from seeds) are elliptical shaped and have a main midrib.² Leaves are opposite, oval shaped, and have short stalks. They are 1 to 3 inches long, hairy, and pinnately compound (having leaflets). Each leaflet is 1/4 inch long.¹

Stem - Stems are numerous, hairy, and up to 6 feet long. They form a dense mat.¹

Fruit/Seed - 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.¹

Roots - Puncturevine has a simple, woody taproot that is the center point all the stems grow from.¹ Seedlings develop a deep taproot within a few weeks.³

Dispersal and Propogation - Puncturevine reproduces by seed, which typically germinate from April to October, depending on conditions (primarily warmth and moisture). Seeds commonly germinate after rainfall or irrigation.¹ A newly sprouted plant can produce seeds within two to three weeks of germination.⁴ Seed production per plant typically ranges from 200 to 5,000 seeds or in some conditions up to as many as 100,000.¹

Dealing with Puncturevine

Prevention

Puncturevine spreads by seed, so limiting the production and spread of seed will prevent new seed from entering the soil seed bank. One way to greatly impact the spread of this plant is by checking bicycle, stroller, vehicle tires, and the bottoms of shoes for burs that may have become attached. If found, simply remove the burs and throw them in the garbage before leaving the area.²

If plants have started to produce burs, do not just pull them and leave them at the site. Even if they look green, some viable seed may have already been produced. Properly dispose of the plants by throwing them away or burning in a fire.²

Susceptibility

The plant is not cold hardy and will die back with frost.⁴ The plant has a deep, somewhat woody taproot, which obtains moisture for growth under conditions unfavorable for most other plants. Puncturevine also requires less water than many other plants.² Puncturevine does not readily emerge from soil depths greater than two inches, but can survive there for up to 4 years.¹ ²

Mechanical 

Hand Weeding - 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.¹ Roots left behind will likely produce additional stems. Try using a hand trowel or shovel to remove as much of the root as possible. Watering the soil before digging or hand-pulling, or choosing to wait until after a rain event, can help soften the soil up, thereby making it easier to pull up the whole plant.²

Mowing - Mowing is ineffective because of the low growth form of the plant.³

Grazing - Grazing is not recommended as plants are somewhat poisonous, especially to sheep.³

Burning - Burning is not recommended as puncturevine’s low growing habit precludes fire as a management option.³

Tilling - 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 seeds 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.¹

Seed Removal - It is easiest to collect seeds after frost has killed the plants and the dry seeds can be vacuumed up with a shop vac or collected from the ground by pressing pieces of Styrofoam or old carpeting on the ground which will pick up the mature seeds.⁴ In areas with an existing seed bank, seed can be harvested by placing carpet or other “sticky” material on boards or a roller that are then applied to or rolled over the soil. With several passes, most of the seed on the soil can be removed.³

Cultural

Plant Competition - Areas with bare ground are ideal sites for puncturevine growth, even with only limited amounts of rainfall.³ Therefore, puncturevine will have an advantage growing in neglected areas like field borders, roadsides, parking lots, and walkways, anywhere plant competition is often limited. To discourage puncturevine infestation, plant areas with site appropriate plants such as a desirable grass along field borders and leave the grass undisturbed.¹ ²

Mulch - The application of 4 to 6 inches of mulch has been used to suppress puncturevine infestations.³ 

Biological

Weevils - 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.¹ Both species of Microlarinus weevils were originally imported from Italy and released in California during the summer of 1961. Subsequent releases occurred across many western states in the early 1960s, including Colorado, Idaho, Kansas, Montana, Nebraska, New Mexico, Oklahoma, Oregon, Texas, Utah, Washington, Wyoming, and Hawaii. Follow-up surveys indicated that weevils had established and spread to adjacent counties in many of those locations. At every location with weevils, seed weevils were more common than stem weevils.⁴

The weevils are sensitive to prolonged periods of frost. Thus, populations of puncturevine may increase after years with cold winters. This is more prevalent in northern states.³ However, the seed weevil was detected in Benton County, Washington in 2003 and has since been found at locations around the Kennewick area (personal observation).² In 2023, some surveys of puncturevine in Idaho, Oregon, Montana, and Wyoming found no weevils nor weevil damage in these locations. Researchers are currently investigating whether cold hardiness or other factors have made it harder for weevil establishment north of Colorado.⁴

Seed Weevil - A female weevil chews a pit in a young, tender goathead, which contains the plant’s seeds, and lays a single egg in each pit; she then covers the egg with fecal matter. The eggs hatch in 2 to 3 days and then the larvae feed on the seeds inside the pod. Multiple larvae can develop within a single goathead. The immature weevils complete their development inside the seed. Seed weevils can develop from egg to adult in 25 to 30 days, with weevils developing more quickly in warmer conditions. Once matured, seed weevils will chew an exit hole in the goathead and emerge. Adult seed weevils feed on puncturevine stems and foliage. New adult seed weevils will mate within a few days and female seed weevils will begin to lay eggs within approximately one week. The average female can lay about 200 eggs, with most of them laid within the first month of adulthood; eventually. Seed weevils can live an average of 96 days, with a maximum lifespan of over 240 days. In warmer regions, seed weevils can have up to four generations in their lifespan, while in more temperate climates, they typically have only one generation. Seed weevils do not attack mature seeds, so collecting mature seeds in the fall and winter will reduce the number of seeds that germinate the following year.⁴

Stem Weevil - A female stem weevil chews a pit in the underside of the puncturevine stem and lays a single egg in each pit; she then covers the egg with fecal matter. The egg will hatch after 2-3 days, and the immature weevil will develop within the stem. Stem weevil development from egg to adult can take 45 to 51 days. Once matured, weevils chew an exit hole in the stem and feed on leaflets and stems. The stem weevils will mate and begin laying eggs within a week of adult emergence with the correct plant and environmental cues.⁴

Host Plants - The host of puncturevine weevils is puncturevine, but in the absence of puncturevine, weevils will attempt to feed on plants other than puncturevine. In forced feeding tests, seed weevils laid eggs on two species of plants closely related to puncturevine, but was only able to grow to maturity on one. 39 other plants were tested that these weevils did not lay eggs on. From these results, these weevils don’t seem likely to go to plants other than puncturevine.⁴

Impact of puncturevine weevils - Several studies have assessed the impact of puncturevine weevils on the reproduction and survival of puncturevine plants. Weevils contributed to the death of about one third to one half of puncturevine plants in research plots by late August, even when plants received supplemental irrigation. Overall, the combined effect of stem and seed weevils reduced flower production by 29% in irrigated plots and 60% in unirrigated plots.⁴

In some locations, up to 80% of goatheads exhibit symptoms of seed weevil damage. Additionally, goatheads affected by seed weevil feeding experience reduced seed production and lower germination rates, even for seeds that appear undamaged. Stem weevils reduced plant biomass and plant survival, especially under dry (unirrigated) conditions.4

Weevil Management - Adult weevils will be able to feed on small seedlings but won’t lay eggs until stems and seeds are big enough to support the development of immature weevils. Adult puncturevine weevils are small and difficult to see, but damage from feeding and weevil development is distinctive. In the early spring, examine the undersides of stems for white feeding scars and exit holes from stem weevils. As goatheads develop, carefully break open the seeds and examine for signs of internal feeding and exit holes. Both species of weevils are active during the daytime.⁴

Adult weevils can be moved by gently digging up infested plants and placing the whole plant or plants in a paper container: a large paper yard trash bag or cardboard box works well for this. Weevils can be held in a cool location, away from direct sunlight for at least a week. As the puncturevines dry out, adult weevils will tend to crawl up or towards light and can be collected by opening the box or bag and brushed or picked out and placed in patches of puncturevine. Adult weevils that emerge later in the summer or early fall will feed on plants but will not lay eggs until the next spring.⁴

Sources:

1. “Puncturevine”, Washington State Noxious Weed Control Board https://www.nwcb.wa.gov/weeds/puncturevine Accessed June 2026

2. Parker, Robert and Boydston, Rick. “PNW 133 Puncturevine”, Pacific Northwest Extension Publishing, April 2020 https://extension.oregonstate.edu/catalog/pub/pnw-133-puncturevine Accessed June 2026

3. DiTomaso, J.M. and G.B. Kyser et al. “Puncturevine”, Weed Control in Natural Areas in the Western United States, 2013, University of California Davis https://ucdavis.app.box.com/s/t266vkfh1ym7bb7j57k5ufkrv9vrby3v/file/2053608376102 Accessed June 2026

4. Bowers, Kristen and King, Joanie. “History and Use of Puncturevine Weevils for Biological Control”, Cooperative Extension Service Publications, February 2025, New Mexico State University, https://pubs.nmsu.edu/_h/H187/index.html Accessed June 2026

5. Murphey, Daniel. “How to Identify Puncture Vine”, Awkward Botany, 25 July 2018 https://awkwardbotany.com/2018/07/25/how-to-identify-puncture-vine-a-k-a-the-goathead-monster/ Accessed June 2026

6. Gunn, Danielle. “Puncturevine: Identification and Management in Idaho”, University of Idaho Extension, November 2025 https://content-hub.uidaho.edu/api/public/content/02da81a4cf824c43948896d952719e6c?v=389c6484 Accessed June 2026