Here is how the University of California (U.C.) describes this pesky weed: “Puncturevine produces many burs (burrs) with sharp spines that can injure humans and animals, as well puncture bicycle tires. (It’s) leaves contain compounds called saponins, which can be toxic to livestock, especially sheep, when eaten in quantity.”
The most effective way to eliminate this weed is to pull it up by hand or use a hoe to cut the plant off the deep taproot. Try to do this while it’s still in the flower stage, before it seeds.
Master Gardeners don’t recommend chemical control for this weed unless you have a large area that is infested and it’s difficult to access for tilling the seedling plants under.
Don’t add these plants to your compost pile. The seeds will survive most composting processes.
If you have plants going to seed you can still pull them up. Just wear thick gloves to avoid injury to your hands, and try not to shake seed heads off the plant.
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.
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.
How would I identify it?
Stems are numerous, hairy, and up to 6 feet long. They form a dense mat.
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.
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.