Whether you call it puncturevine, goathead or sandbur, it is a pain - literally. This mat-forming annual weed has hard spiny seeds that can poke holes in bicycle tires or shoes. Dogs and other animals that get a goathead in a foot start limping immediately or stop altogether until you remove the spine.
The stems on this low-growing problem weed can reach 5 feet or more in length. Seeds stay dormant in the soil for four to five years, making eradication difficult, unless you are diligent. Since the tack-like seeds readily attach to animals, vehicles, clothing and shoes, this nasty weed is easily spread. A large plant can produce up to 10,000 seeds, which means lots of new tire-puncturing plants can grow.
According to Carson City Weed Coalition coordinator Margie Evans, puncturevine is on Nevada's noxious weed list. However, because puncturevine is everywhere, the law doesn't require that it be controlled. It would take too many people to regulate.
Long-term control of puncturevine relies upon the elimination of the seed bank. Since the plant grows close to the ground, mowing is ineffective.
Hand-pulling is effective on small infestations if you pull it year after year before it goes to seed, until the seeds are gone. Hoeing and shallow cultivation can work before flowering. Tilling, however, buries seeds that remain viable for years.
If there is an existing seed bank, it may be useful to remove the seeds by dragging the area with a piece of carpet or other material on boards or a roller. Several passes will remove most of the seed on the surface. Be sure to dispose of the carpet or material where seeds can't sprout.
Pre-emergent herbicides help reduce infestations if applied and watered in to the soil in late winter. Note that these herbicides will control all germinating seeds, not just weed seeds. Post-emergent herbicides such as those containing 2,4-D or glyphosate will control existing plants.
For all chemicals, read and follow the label directions to determine rates and timing of application. Applying the chemical too early or too late won't control the weed.
University of Nevada Cooperative Extension specialist Sue Donaldson will teach a free class "Season Extension" in the continuing "Grow Your Own" series 6-8 p.m. Oct. 18, at Cooperative Extension, 2621 Northgate, #12. Find out about cold frames, plastic mulch, floating row covers, sanitation and crop rotation.
To reserve your spot, please call 775-887-2252.
• JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce
.unr.edu or 775-887-2252. g
