Q: My yard is covered in “Horrible Evil Spiky Seeds of Death,” as we call them, though I’m sure that’s not the technical name. I think they come from the pictured tree. Humans can’t go outside without spending several minutes prying the damn things off their shoes. Dogs literally weep doggie tears to walk out there. Is this tree some kind of precious native specimen or can I burn it to the ground (metaphorically) without the stain of eco sin on my soul?
A: Your Horrible Evil Spiky Seeds of Death are also known as Tribulus terrestris, goat head, puncture vine and other words unsuitable for a family newspaper. They didn’t come from a tree but from a small green plant that grows prostrate to the ground. It’s a summer annual so all you see now are the seeds. Once they germinate and begin to grow, you will notice the green foliage and eventually the nice yellow flowers from whence the seeds develop. To step on a seed is very painful, as your dog would say if dogs spoke English. They are able to puncture some bicycle tires and so they are not well-liked by humans either. I switched to thicker tubes to reduce the number of flat tires. You can keep the tree and still wage war on the guilty plants by pulling them out of the ground as soon as you see them so they won’t produce more seed. Some people prefer to use an herbicide and any broadleaf variety will do. Please follow the label instructions for any pesticides you use to prevent injury to any non-target organisms.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to tucsongardensage@gmail.com
