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Puncturevine plants can get a foothold at the exposed edges of lawns, or in exposed soil or gravel areas, and spread out onto walkways and garden beds for several feet if not controlled.

Courtesy Meredith Seaver

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Puncturevine burs can puncture or pierce tires and shoes, or cling to clothing or fur and be carried to new areas, spreading an infestation.

Courtesy Eric Coombs, Oregon Department of Agriculture, Bugwood.org

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The best time to control puncturevine is when the plants are young, before the small, yellow flowers appear and set seed.

Courtesy Meredith Seaver

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We received two questions about the same weed this week:

I have been battling goat head burrs in a 1/3-acre plot of fallow land. I kept ahead of them until the last month or so and now they have come in with a vengeance. I am going to spray again with glyphosate, which does a pretty good job. My question is: After spraying them, would it do any good to follow up with a preemergent?

These dang weeds in my pictures are taking over along the edge of our lawn and into our parking lot. I tried lawn weed killer … no effect. I can’t figure out how to destroy them. Any help would be appreciated.

You’re both dealing with a weed called puncturevine or goathead. Puncturevine, Tribulus terrestris, is an aggressive, fast-growing annual weed that drops small woody burs with sharp, strong spines that can easily puncture bike tires, thin-soled shoes and the bare feet of people and animals. It’s well-adapted to dry locations, making it a common weed in fallow areas and other locations with dry, exposed soil. As an annual plant, puncturevine will die at the end of the season, but its seeds can be viable for several years, making it seem like a perennial problem. Unfortunately, there isn’t a “spray it and forget it” solution to the problem.

Because puncturevine spreads by seed, the most important control method for home gardeners is to prevent flowering and seed production by hand pulling, hoeing, string trimming or spraying an herbicide early in the summer while plants are young. If any of the plants do have little yellow blossoms, taking the extra time gathering up all the weeds you’ve pulled or hoed, bagging them, and disposing of them will pay dividends in the long run.

If weeds have been growing along sidewalks, driveways, pavement or on hardpacked open soil, you can also sweep up or vacuum up as many seeds as possible to reduce the number of seedlings next year. In large fallow areas, a leaf blower may be helpful in coaxing the burs into a single group for easier collection. Some gardeners choose to drag burlap or old carpet through infested areas to snag the puncturevine burs.

Whenever you’ve been working in an area with puncturevine, check the soles of your shoes, wheelbarrow tires and loose clothing before you step into other parts of the landscape. Puncturevine burs can be carried into “clean” parts of your yard and garden where they can fall off and germinate.

Post-emergent herbicides like glyphosate or a broadleaf herbicide with a dicamba/2,4-D combination are your best chemical options if applied before the weeds bloom and set seed. Glyphosate is the better choice for vegetable gardens, as broadleaf (lawn weed) herbicides aren’t intended for use around edibles and may have a lengthy replant restriction. Regardless of which chemical options you may choose, read the label carefully and follow all the directions so that you avoid drift problems and off-target plant damage.

In the spring you can try a preemergent herbicide to prevent seed germination. The active ingredients in many weed preventer products have limited effectiveness against puncturevine, so it won’t be a successful control strategy on its own. There are other things you can do to reduce seed germination, though.

Exposed soil is an invitation for weeds, including puncturevine. Keep exposed soil in the infested areas covered with some kind of mulch to block sunlight and discourage weed seed germination. A 1/2-inch layer of compost works well and doesn’t need to be removed if you decide you want to plant something there later. Refresh the compost every spring or whenever it looks like the layer is getting thin.

Planting and maintaining healthy groundcovers or bedding plants in weedy areas will also help to reduce puncturevine populations by shading the seeds and competing with young seedlings.

A combination of multiple control methods is the most effective to eliminate this troublesome weed. Consider all the options we’ve mentioned, choose the ones that best fit your landscape situation, and be consistent and persistent.

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