Should I kill my weeds by peeing on them?
Q. I live in an ecosystem where native plants are perpetually engaged in epic competition with invasive plants. I also find myself frequently peeing in nature, often with the opportunity to pee on the plant of my choosing. If I want to encourage some plants to thrive (like natives) and discourage others (like invasives), which plants should I be peeing on?
I want to consider factors like the salt and other dissolved minerals in my pee. And does it matter if I pee on the roots or on the leaves? Does the species of plant affect the question of to pee or not to pee?
Though one particular pee might hardly make a difference, just think of the effects from huge numbers of conscientious pee-ers!
Santa Cruz, Calif.
A. Dearest Jeff,
I am delighted to report that with your question, I can finally start a folder entitled Creative Ways to Battle Invasive Species. First, we discussed feeding them to our dogs; now we turn to peeing on them. What’s next, dear readers?
I suppose there’s a chance you might be poking fun at this very serious advice column, Jeff, but I’m going to answer your question anyway because it raises some interesting issues about ecology, agriculture, and water use. That, and writing me a question is akin to joining my circle of trust. So let’s proceed.
For plants, human urine can be a blessing or a curse, depending on amount, concentration, soil composition, and plenty of other variables. That yellow stream is mostly water, but it also contains nitrogen, potassium, and phosphorus, which just happen to be the key ingredients in garden fertilizer. Knowing that, then, is it any wonder that some gardeners have been using it for years as a treat for their tomatoes, and that go-getting researchers have experimented with large-scale pee-collection projects in lieu of chemical fertilizers? A group of Finnish scientists grew bigger beets with sprinkled urine than with mineral fertilizer. Apparently proving a wee change can make a big difference.
It’s free, it’s abundant, it supersizes your snacks – what’s not to love?
There is one thing: salt. We all excrete some salts (Westerners in particular because of our diets), which harm plants in high enough doses. There’s another thing, too: Though nitrogen makes your garden grow, too much nitrogen all at once makes your garden turn all yellow and shriveled (a classic case of overfertilization, or “root burn”). So we need to be careful about how we’re applying your homemade solution to invasive weeds, Jeff.
For some clarity, I turned to Carol Steinfeld, author of Liquid Gold: The Lore and Logic of Using Urine to Grow Plants. Would peeing on invasive species help drown them out? “Enough urine will kill anything,” she said. “But one application of urine is unlikely to kill anything. You can attempt to eradicate some invasives by consistently peeing on them, but it will take a lot of pee. It won’t be a one-shot deal.”
So if you’re out hiking and nature calls, answering that call all over the occasional exotic plant will probably not help the cause. If you and a bunch of friends teamed up on the same plant, making sure to saturate the roots, well, maybe (Steinfeld estimates about 6 cups of undiluted urine in one day would do the job on one dandelion). This only works if the plant in question is not one that loves nitrogen, like bamboo, by the way. But clearly, this approach is not exactly efficient for restoring ecological balance to the wilderness.
Okay, well, what about peeing on native plants to give them a shot of nourishment? Again, you’ll have to do your research: If the species loves nitrogen, then sure. If it’s particularly delicate, undiluted urine might not do much for it. Make sure to get in touch with local experts on native and invasive plants to find out more before attempting any kind of native plant Johnny Appleseed campaign. Even so, your biggest environmental impact in al fresco peeing is probably just not flushing the toilet.
But you know what would help, Jeff? Volunteer for a weed eradication project with a local conservation outfit – it just so happens California Invasive Species Action Week is coming up. In some places, you can even lend your teeth to the cause by eating them. We need every weapon we can get in the epic battle against invasive species, but unfortunately, urine is just a drop in the bucket.