1 - Corn gluten meal and manual removal of seeds and seedlings can be non-toxic and relatively safe ways to manage goathead (puncture vine) weeds.

Yard and Garden June 14, 2014

Q.

I have millions of goathead seeds in my yard. I am looking for a safe, non-toxic method of removal. What would you recommend?

A.

A product called corn gluten meal is a natural (made from corn) preemergent herbicide. It kills the roots of seeds as the seeds are germinating. It is not selective, so it will kill seeds you intentionally plant as well as weeds.

You can use it around transplants in the vegetable and flower garden because their roots are already formed. It will just inhibit root development in germinating seeds.

I could not find a label that specifically listed goathead weeds (properly called puncture vine). However, the labels said it kills "most lawn weeds" with warnings that it will kill intentionally planted grass seeds and vegetable/flower garden plant seeds as well. It needs to be applied during a dry spell with no rain for 5 to 6 days, but that should not be a problem in New Mexico now. When/if the monsoon arrives, timing will become more critical.

The quantity of seeds in the lawn may be diminished somewhat (not totally eliminated) by dragging burlap or old carpet through the lawn area. These fabric materials should collect some of the weed seeds and may be burned or disposed of away from the lawn. Any seeds that have already germinated will need to be pulled manually before they blossom and form seeds. Residual seeds that are not collected by the fabric, but are dormant and do not germinate this year may create problems in future years. So, you will need to watch for seedlings and treat for several years. The potential for future infestations will diminish yearly if you allow no puncture vine plants to develop to the point of producing new seeds.

I hope the corn gluten meal works for you. As I said, I could find no listing of puncture vine as one of the targeted weeds. The general statement that said it was for controlling most lawn weeds, and the fact that its mode of action is to kill the roots of germinating seeds, this product is a possible answer to your problem. Other, synthetic, preemergent herbicides are labeled for this purpose if the corn gluten meal fails, but most of these products do not meet your "non-toxic" criteria. The manual removal of the puncture vine seeds with fabric or carpet remnants may not meet the criterion of safety. You are likely to find your skin punctured, so wear shoes, long pants, long sleeves, and leather gloves when dealing with the removal of seeds.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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