LOGAN, UT – There is a reason “puncture” is in the term puncturevine. If you have ever stepped on puncturevine seeds (commonly known as goatheads) with bare feet or run over them with a bike tire, you know they truly do puncture. With the scientific name of Tribulus terrestris (a tribulation on the earth), no name is more appropriate. 

Native to southern Europe, puncturevine belongs to the caltrop family. A caltrop is a metal device used by the military and police to stop vehicles with pneumatic tires. It is made with four spikes so that when three spikes are on the ground, one always points into the air. Goatheads are similarly formed.
Puncturevine is an annual weed that germinates all season and can produce a plant
that is 2 to10 feet in diameter. It does not root at the nodes but spreads out like a carpet, always prostrate and never very erect. A typical large puncturevine plant can produce from 200 to 5,000 seeds in a season. Seeds from the current year and seeds in the soil seed bank germinate when conditions are right. They prefer hot conditions and will germinate whenever they get a small amount of water.
Consider these tips for control.
• Control in the home garden or yard is primarily mechanical, usually by digging or pulling plants. Puncturevine plants often grow in a gravel driveway or an abandoned area by the edge of a road or sidewalk. When they are actively growing, it is possible to fold the sprawling parts of the plant back on the center of the plant, cut the taproot with a shovel or hoe and remove the entire plant. 
• If the plant has gone to seed, one of the best control tactics is to use a broom to sweep the seeds and collect and discard them. Seeds can also be removed from an area using a wet-dry vacuum. Physical removal of the seeds and plants is approximately 90 percent effective for control.
• Herbicidal control is also possible, and puncturevine plants are susceptible to 2,4-D, glyphosate, and dicamba. These herbicides are not 100 percent selective and generally are not used in the yard or garden because they cause too much damage to desirable plants. 
However, in open areas such as driveways, these herbicides can be sprayed very successfully on puncturevine and are most effective when the weeds are small.
• As far as biocontrol, puncturevine-eating weevils have been used with success in some states, but in Utah they do not seem to be widely dispersed and active.
• Other unique control methods include using old pumpkins at the end of the year. If you roll pumpkins over the infested area, goatheads get stuck into the flesh, then the pumpkins can be thrown away. An old piece of carpet works in the same way by gently pressing it onto the area that is infested with puncturevine, then pulling it away as it becomes covered with the seeds.

By: Ralph Whitesides - May 16, 2012