"Your bike's flat tire was caused by a goathead, see this? If you want to ride a bike in Arizona, you need to put Slime in your tires." (Slime is a sealant used to plug punctures in bicycle tires.) I examined the peculiar little object: hard and lumpy, about a quarter of an inch across, sporting two stout spines with surgically sharp points.
"Yes, I see. I'll take the Slime."
One fall day I noticed I had dozens of those goatheads stuck in the soles of my boots. Where had they come from? Not far to look. Numerous plants occupied a wood-chipped walkway right outside my door. Each within a circular pile of seeds, they were the advance front of an infestation originating in the backyard. Chilled, I thought, what if these things keep spreading? My place would be unlivable, as if truckloads of tacks had been dumped all over. I knew what must be done. I addressed them: "All right, you goatheads, this ends here."
They smiled complacently and replied, "You're a negligent homeowner. You never even check your backyard. We came two years ago in construction sand. This place suits us very well. There is no competition from other plants. The soil is loose and disturbed. There is a large cindered area before us. We will like that, too. Each of us can create hundreds to thousands of new plants. Our seeds don't germinate all at once, so there will always be some that catch the best conditions. We grow flat on the ground, so you can forget about mowing or weed-eating. And you will serve us! We'll pierce your boots and car tires so that you will spread us wherever you go. There is no way your short-lived human resolve can defeat our biology."
We'll see about that, I thought. My biology gave me the opposable thumb.
"Horrendous, evil, savage, vicious, most obnoxious weed on the planet, nastiest, sharpest, thorny thing I've ever seen," are reactions posted on the internet regarding this plant. "What are these things, and how can I get rid of them?" are the plaintive queries. And words regarding removal: "Diligence, determination, persistence."
Tribulus terrestris, native to temperate parts of Eurasia, is believed to have arrived in the U.S. over a century ago, carried on the wool of imported sheep. Listed as a noxious plant, it has spread throughout the western states. Its vines radiate outward, up to 6 feet long. It produces small, yellow, five-petaled flowers, followed by clusters of goatheads, the seed-containing structures. They sprout in our area after sufficient monsoon rains have fallen and stop growing with fall dryness and frost.
To eliminate an infestation, for three to seven years, all newly sprouted plants must be pulled up or sprayed with herbicide every couple of weeks, to prevent any more seeds.
An effective way to kill both plants and seeds in an infested area is to burn them up with a propane torch. As you can imagine, extreme caution is recommended with this method, including burning only during conditions of low fire danger, and removing other combustibles from the area.
For out-of-control, large-scale infestations, one may purchase over the internet, two types of species-specific weevils, which kill the seeds and vines. This does not result in total control but can greatly reduce plant numbers.
At our place, we pulled up thousands of goathead plants in the first three years. This year, the fourth, our goathead patrols have produced less than 100 plants and very few seeds are left to stick in our shoes. So it works!
"Maybe this wasn't such a great place for us goatheads after all!"
Maria Horton and her husband Charlie, a mental health therapist, enjoy living and writing east of town among the pinions and junipers. Dana Prom Smith and Freddi Steele edit Gardening Etcetera. Smith blogs at http://highcountrygardener.blogspot.com and email at email@example.com.