Goathead

According to its wikipedia article, Tribulus terrestris has many names: bindii, bullhead, burra gokharu, caltrop, cat's head, devil's eyelashes, devil's thorn, devil's weed, goathead, puncturevine, and tackweed. That the plant has three names that use the word “devil” isn't surprising to those of us who share an ecosystem with it. The contrarian in me wants to find something good about this plant, but I can't. And right now it's in season.

Since learning how to identify them last year, I've watched with both fascination and dread as goatheads have grown like the weeds they are all around town. They're easy to spot, with their ground-hugging stems and tell-tale dark green leaves that shout from fifty feet away: “I'm not native to the Sonoran.” The mature plants that have budded dozens of bright yellow flowers are handsome, though right now most of the goatheads around town lack flowers. I suspect they're waiting for a monsoon rain for nourishment before releasing their devil thorns wholesale.

The plant is especially woeful to cyclists; the seeds' tetrahedral shape causes them to land on the ground such that at least one thorn is guaranteed to stick up, waiting to hitch a ride in a tire. The thorn is sharp and hard. Though I can crush a seed between a rock and asphalt, it takes some manly strength to do so. So a seed that pierces a tire and hitches a ride is not damaged by the ordeal. This plant is good at invading.

During the last few weeks I've been uprooting all but the biggest plants I've seen while on my way to or from work. I've destroyed plants along the jogging trail on North Central Ave, along the canal, in the canal path in cracks in the asphalt, and in people's front yards. The plants that grow alongside roads and canal paths are especially destructive: their stems creep onto the road or path, where the plant gains direct access to passing rubber and a free ride. Fortunately, those plants tend to be the sickliest and can be pulled up by the root more easily.

Here's an example of a goathead creeping onto the canal path:

And here's one that I uprooted. You can see that it has only a few flowers and seeds. But in another month this plant would likely have a hundred seeds and have caused countless flat tires.

I uproot the plants with brute force, yanking them out of the ground with my hands. Sometimes I get a clean pull; sometimes the plant breaks off at the root. But I believe that both forms of trauma kill the plant; the plant is not hardy.

Is my fixation with killing goatheads doing any good? Probably not. But it's fun to kill goatheads, and every kill gives me an irrational feeling of accomplishment.