Puncturevine (Goatheads): What, Uses, and How to Get Rid of Them.

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It’s mid June to the end of October where evil comes in the form of Puncturevine here in Zone 5.Puncturevine puncturevine center Seeded puncturevine

When we bought our house, the lot had less landscaping than it does now. Previous owners sprayed, and probably that’s about it. Nearly the entire lot (3/4 acre) is covered in puncturevine seed. Come June, I’m scrutinizing our garden and major walkways for that little telltale seedling, that in many areas seem to come up as ground cover. By this time, August, I’m pulling, scraping, hoeing. We’d be burning too, except we’re in a very strict burn ban til probably October due to wildfires and extremely dry conditions.

Tribulus terrestris

This nasty thing is also known as caltrop, tack weed, puncture weed, Mexican sandbur, Texas sandbur Burnut, bullhead, goathead, cat’s-head, and devil’s thorn. I call it Bastard. There is no use use for this plant that I found except to be a pain in everyone’s asses. (Holy crap tribulus is known for aphrodisiac, antibacterial, and anti fungal properties in Ayurvedic medicine. Screw that. I hold a grudge against this weed and will treat it thusly. For good measure, here’s a study on tribulus and rat sexual activity)

Puncturevine is considered an invasive species in Washington state (unlike other herbs, I will treat it as one regardless of properties). It can grow in dry conditions, anywhere where there is no ground cover or barrier.

It grows particularly well in sandy, compacted soil (which is our soil). The plant grows from one deep root, spreading outwards in every direction. Each tendril can grow up to 10 feet long. The leaves are ‘elliptical shaped w/ a main rib’. Flowers are small and yellow; the 5 petals elliptical. Shortly after it flowers Bastard will seed, into soft green burs in bunches of 5. These turn brown and harden, and hurt like a bitch if you come across one (or a giant pile). One plant can produce THOUSANDS of seeds.puncturevine seed

This hardened exterior protects the seed from damage, thus allowing it to live in the soil for years. This is one reason why most people that take the money and time to scrape off a foot of soil from their property find seedlings pop up yet again the next season. Deep tilling and scraping can bury seeds, which can lay dormant for years.  It cannot be eaten by livestock; it is toxic to some.

Intervention and prevention

NWCB recommends the following 4 techniques to try (and of course you’ll get my commentary):

  1. General control: Making sure you’re not carrying seeds to and fro on tires, shoes, clothing, etc. Don’t bike where there’s an infestation. NO SHOES ON IN THE HOUSE. #1 Rule here. This is why. We have a large rug at the back door and a bucket for shoes. The majority of the seeds will stay on the rug, thus vacuumed up. Unfortunately I haven’t invested in any doggie boots for the dog yet, so he tracks them in.
  2. Mechanical control: Handpulling, hoeing, etc. Preferably before seeding, ideal before flowering. Over a horrendous amount of time. Years. Decades. WEAR THICK GLOVES. On occasion I get lazy, forget my gloves inside, and use my bare hand. DO NOT DO THIS ON A PLANT THAT HAS SEEDED. My fingertips hurt. Don’t feel my pain.Puncturevine flower Puncturevine
  3. Biological control: “The puncturevine seed weevil, Microlarinus lareynii, and the puncturevine stem weevil, Microlarinus lypriformis are two biocontrol agents that can provide good control when used together. The puncturevine seed weevil larvae destroy developing seeds and the adults can cause damage by feeding on stems, leaves, flowers and fruits. The puncturevine stem weevil larvae feed within the stems and root crowns and the adults feed on the stems and leaves. Both of these insects may have a harder time establishing in climates with cold winter temperatures.” (source) Form printed and nearly ready to submit for approval. We have not tried this but have considered. I’m ready. Bring it on.
  4. Herbicide control: There are supposed to be various herbicides that help kill off puncture vine.  We have not tried these, nor do we have interest. We’d rather try the weevil.

Other things to consider:

  1. One thing that was not on this list that we tried this year was a mulch or barrier. We tore the carpet out of one room in May, and put it and the padding out in the heavier traffic areas where we had issues last year. Even after moving them we haven’t had anything pop up yet. However, you can see where the barrier ended- a strip of puncturevine right there.puncture vine growth around barrier
  2. I’ve heard of goats helping battle puncturevine, hence the nickname ‘goat head’. I’d assume they eat the plants, but I don’t know anything about goats actually being able to safely ingest the seeds.
  3. Burn ’em. Burn ’em dead. High heat for extended periods of time will kill the seeds. A propane torch works- we did this last year in a couple places. The infestation was not as heavy in these areas this year. Soo it didn’t eradicate it; maybe we needed to burn longer. We’ve also been putting the plants we pull into the firepit for when we can burn them there. puncturevine seed

Whatever method you choose, the timing seems to be what is most important. Get them before they seed. Preferably as seedlings, not when they’re nearly there. puncturevine seedling puncturevine seedling root puncturevine seedling

Have you battled puncturevine? What did you try, and what helped? I want to find SOMEONE that has eradicated completely. Haven’t heard anyone yet.

Sources:
  1. Noxious Weed Control Board WA State 
  2. WSU Puncturevine publication
  3. UC IPM Pest Management
  4. About.com AltMedicine
  5. Goatheads.com

 

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