Getting rid of goat head
We are amending the soil soon and want to plant grass in the spring. We want to get rid of the goat heads now what’s the best way to do that? Thank you!! Susan
Denver County Colorado
Goat head is also known as Puncturevine, Tribulus terrestris. It is classified as a Class C Noxious weed by the Colorado Department of Agriculture.
Puncture vine is difficult to eradicate from wherever it's growing, mainly because it can build-up a "seed bank" in the soil. Seeds can remain viable for 7-10 years.
There are ways that you can work to try to control it - persistence is the key.
Chemical controls can be used. Because puncturevine is an annual that does not winter over but grows from seed each year, you could apply a pre-emergent herbicide in the spring to prevent the seeds from sprouting. The tricky part for your situation is the timing of using pre-emergent chemical controls. If you are also seeding a new lawn, any preemergent herbicide will also prevent your grass seed from sprouting. Application of a preemergent herbicide in late March could help to reduce the number of puncturevine plants that germinate and you could plant your grass later, in April or May.
If you are laying sod for the new lawn, the preemergent would work on the puncturevine seeds and not affect the sod.
If you get puncturevine in your new lawn, you can mechanically dig them out, preferably before they flower and disperse seeds- but you need to be on top of this throughout the growing season. You don't want to let any more plants mature seeds that add to the "seed bank." You could also use post-emergent herbicide on weeds that grow up in the lawn. The weed-n-feed type products for lawns are effective in killing broadleaf weeds.
Attached here are some links that discuss control of puncturevine in more detail.
Best of luck with your goat head,
Thank you SO MUCH for this information! You mentioned that chemical controls can be used. What are some names of recommended chemical controls? I asked at my local garden center and they only carry one product and they said it should "probably" work.
It sounds like, if I am reading your email correctly, that I do not need to do anything this fall before augmenting my soil with compost, mulch, leaves, manure and rototill it. I am concerned about rototilling those seed pods throughout my yard. I have the materials in the back yard waiting for the rototilling because I wanted to check with you first.
So the existing (dead) goathead - can I just pull them up or mow them down or just rototill them in?
But if all I need to do is the pre-emergent in the spring, then we are good to begin the roto-tilling.
Controlling puncture vine is all about getting on top of the seeds: seeds of the current crop of plants plus the seeds from previous crops of plants that are hidden away in the soil waiting for conditions to be right so they can germinate.
This fall, rake off the area (or mow with a catcher attachment) to remove as much of the 2017 crop of plants with their seeds as you can before you rototill.
Next spring, use a pre-emergent to kill germinating seeds to prevent new plants from growing.
Next summer, hand-pull young plants that weren't killed with the pre-emergent in order to remove them before they flower and produce more seeds. If there are too many plants to hand-pull, use a post-emergent herbicide product labeled for puncture vine.
Because puncture vine seeds from pervious years will remain viable in the soil for 4 or 5 years, continue killing seeds/plants as they emerge in subsequent years until all the seeds in your soil are exhausted. It is key to controlling this noxious weed that you not allow new plants to grow, go to seed and start replenishing the seed supply in your lawn.
Look at Page 2 of this fact sheet on Puncture Vine. Down at the bottom is a chart of different chemical herbicides you can apply next spring and the timing of when it is best to apply them: https://www.colorado.gov/pacific/sites/default/files/Puncturevine%20Factsheet.pdf