How to Get Rid of the Toughest of Weeds
Weeds have developed traits that make then top-notch survivors, allowing them to colonize and choke out weaker competitors. Learn how to beat the worst weeds.
How to Control Puncturevine
Puncturevine’s name describes it perfectly.
This weed is a vining ground-hugger whose arms can stretch out five feet or more, and it’s one with seed burs so stiff and sharp that they can puncture a bike tire or toe.
Although puncturevine can be found in most U.S. states, it’s a particular problem in the Pacific Northwest, where it shows up along roadways, in pastures and meadows, in home lawns and gardens, and any open area where the soil has been disturbed.
It’s a fast grower that isn’t deterred by poor soil or hot, dry conditions.
Puncturevine is native to southern Europe as well as Africa and parts of Asia. It’s long been established in the U.S. and is troublesome enough to earn placement on some states’ Noxious Weed Lists – Arizona, California, Colorado, Nevada, North Carolina, Oregon, and Washington among them.
Besides being a nuisance and a potentially blood-letting weed, puncturevine is toxic when eaten by livestock – especially sheep.
Puncturevine with yellow flowers. Photo by Richard Old, www.XIDservices.com
Getting to know puncturevine
Puncturevine (Tribulus terrestris) is a summer annual weed, also commonly known as goathead, that typically emerges from seed in mid-spring (May in much of the U.S.) In warmer, frost-free climates, it’s a plant that can become a perennial.
New plants put down a deep, central taproot while sending out multiple stems that snake their way across the ground.
The plants are distinctive for their small, elongated leaflets that form opposite one another in pairs of four to eight along the skinny stems.
About a month after plants emerge, small, yellow, five-petaled flowers open. About two weeks after that, the flowers morph into pea-sized burs with sharp, woody spines that are sharp enough to puncture leather and rubber and can injure people and animals. Those are what particularly nail down puncturevine’s identity.
The spiky seed burs aren’t readily visible, though. They’re mostly hidden under the arms of green foliage where they’re easy to step on or grab before humans realize the bloody threat.
The spiky seed pods can stick to shoe soles, clothing, and animal fur, too, helping disburse seeds into new areas of spread. When mature, the seedpods separate into several brown sections, with 2 spines each.
Puncturevine is a prolific seed producer, too. Each plant is capable of producing at least hundreds of seeds with some estimates claiming up to 100,000 potential seeds per plant per year.
Puncturevine spiky seed bur. iNaturalist
Solving a puncturevine problem
Puncturevine is a weed that’s a top example of the axiom to eliminate weeds as early as possible. As an annual, a young puncturevine plant is fairly easy to pull or hoe.
However, if you wait for the plant’s taproot to form, give the fast-growing arms a few weeks to grow, and especially wait until the spiky seed burs form, puncturevine becomes a foe that fights back.
If you try to hand-remove puncturevines in summer or fall after seeding has occurred, be sure to wear thick gloves and be careful of stepping on seeds that may have fallen. This is not a weed to tackle while wearing flip-flops.
Puncturevines are vulnerable to a variety of weed-killers, so spot-spraying is another option. Be aware that although these sprays usually kill the current year’s vegetation, they won’t stop any dropped seeds from sprouting next year if you sprayed after the seeds matured.
Also be careful when removing dead mature plants since those spiky seeds might still be lurking underneath.
Read product labels for safe use and to be sure the herbicide you’re considering is labeled for control of puncturevine.
Remove puncturevine plants before they have a chance to flower and set seed. iStock/ Getty Images Plus
Preventing future trouble
Since puncturevine depends on seeds to grow from year to year, the first strategy is to kill or remove plants before they have a chance to flower and set seed. That will limit the future sprouting of potentially thousands of new puncturevine seedlings.
Limiting the tilling, digging, and disturbing of soil can discourage the sprouting of puncturevine seeds already in the soil since most of them germinate from close to the surface. The plant’s seed can remain viable buried in the soil for five to seven years, so not disturbing the soil prevents stirring dormant seed closer to the better-sprouting surface.
As with all seeding weeds, covering bare soil with mulch or groundcover plants is another strategy that discourages seed germination.
A third avenue of prevention is applying granular weed preventers.
Preen Garden Weed Preventer, for example, is labeled for puncturevine prevention for up to three months per application, along with 36 other common weeds. Granules can be spread over 450 existing landscape plants without harming them.
For best puncturevine control, apply Preen in early spring (before seeds germinate) and then water lightly after application.
