Dog pee: Why it’s bad for city plants and how to get dogs to urinate elsewhere.

This is Explainer, a column that answers questions we all have. Outside the Slate offices, there are well over a dozen yellow signs in the plant beds that read, unequivocally, “PET-FREE ZONE.” The sign that piqued my interest, though, was one at the base of a tree in Manhattan that denoted the reason behind the vitriol: “DOG URINE KILLS PLANTS.” That’s when I started to notice that city trees have been equipped with a variety of defenses against their urinating foes. Parks Department rules state that no person should “kill, carve, prune, or inflict other physical damage to the tree,” which can result in fines, but dog urine doesn’t fall into that category. If your dog starts to pee on an unsuspecting shrub, give a command like “Let’s walk,” suggested Mary Burch, a certified applied animal behaviorist, in an email. To understand where else dogs could be peeing, we can look back to the 1930s, when the phrase “Curb Your Dog” came into common use in New York City—not a very clear imperative, given the multiple meanings of “curb.” It turns out people have been confused by it for decades.