"Creeping Charlie" — the Lawn Weed With Many Names
Q. Mike: I am so sick of the "creeping Charlie" in my yard! The more I try to get rid of it, the worse it gets! I have a mulching mower and I think maybe that is spreading it even faster (although I bag my clippings in the spring, when this crud is most dominant). I have tried borax; weed and feed has no effect; and I've de-thatched in spring with a fine comb rake. The raking seemed to pull out a lot of the plants, but it came back even stronger! Any solutions? I'm about to just sell the place and start somewhere else!
- ---R.J. in Bonne Terre, Mo.    (pronounced "Bon Tare"; it means "Good Earth")
- ---Sue in Meriden, CT
A. Yes, Sue—we will email you a copy of this answer; but you have to promise to call that local NPR station and badger them to pick up our show—or we'll seed some of your Creeping Charlie in their coreopsis!
That's right; despite the vastly different common monikers, you and R. J. have the same pesky weed—a nasty vine that just may have the most aliases in the plant world. In addition to "creeping Charlie", it's also called "Cat's Foot", "creeping Jenny", "hedge maid"; "Robin Runaway", "Lawn Ivy", "Ground ivy", and the truly weird "Gill (all) over the ground", which in some regions has become "Ground over the Gill".
Its 'real' name is Glechoma hederacea, and in her 2002 book, "Weeds, friend or foe?", our friend (not foe) Sally Roth calls it "one of those frustrating, invasive weeds that make committed organic gardeners wish they could reach for an herbicide." Fortunately to the ears of this organic gardener, the nasty chemical versions of those things don't work very well against this foe either, says Iowa State University turf grass expert Nick Christians, Ph.D. We'll hear more from Nick in a minute.
Once considered a useful ornamental groundcover, especially in shady areas, its pretty blue flowers are a great attractor of birds—and bees who will pollinate your wanted plants. And Sue is correct that the flowers are used in herbal medicine, specifically in headache remedies, which seems appropriate: It causes them; it cures them.
Dr. Nick Christians returns to explain that Sue cannot have it both ways; allow this colorful lawn-alternative groundcover to remain in place of (or overtop of) turf and it will continue to invade your compost, flower beds and everywhere else it can reach, including neighboring yards, which could well trigger a neighbor-war. Hand-pulling will control this pest, he says, but only with persistence. Pull it out as soon as you see those distinctive scalloped leaves—and be sure and wear gloves when you do. Nick adds that some people are highly allergic to this member of the always-aggressive mint family.
It does spread by seed, so yes, mowing it after those Springtime flowers appear is a lot like deliberately planting more. But mostly it spreads by creeping along the ground, sending the occasional root down deep into the earth. It is from these stygian roots, explains Nick, that all of those seemingly dispatched plants reappear.
It is this weed's seeming invincibility that led Nick in the early 1990s to try attacking it with a number of commercial herbicides and the 'home remedy' our Missouri listener mentions in his missive: The famed 'Borax cure'. Through trial and error, he and his students discovered that there was some truth to the stories about good old Twenty Mule Team Borax controlling the weed. Ah, but Borax—a labeled pesticide for use against ants and roaches and an essential micronutrient labeled for use in fertilizers—is NOT labeled for weed control, and so people like Nick are forbidden to recommend such a thing.
"We posted a little report on our study on our website, and the University is always after me to take it down," he explains. So this is NOT a recommendation. As Nick explains, it is just 'talk'—a little cracker-barrel discussion of a little something he and his students tried. He is not in any way suggesting that our listeners do this.
But when you do, measure carefully!
Most gardening is like cooking—you're a spineless weasel if you measure things precisely. Some gardening, however, is like baking; fail to measure and you blow up the kitchen. This is like baking, explains Nick; just the right amount of borax and the weed is killed with minimal damage to the lawn; too much borax and the lawn dies; too little borax "and Charlie keeps creep, creep, creeping aloooong!"
To treat an area of approximately one thousand infested square feet, dissolve 10 ounces of Twenty Mule Team Borax in four ounces of warm water. When you have all the borax in solution, mix this into two and a half gallons of warm water, stir well, and spray directly on the weed with a sprayer that has never held chemicals of any kind! (One that you've used to apply non-toxic things like deer repellant, compost tea, or beneficial nematodes is fine; just remember to always clean your sprayer after every use, including this one—you don't want any residual borax in there.)
You'll get the best results when the weed is dry and rain is not predicted for a few days afterward. And be vigilant when any new runners appear.
And remember—you didn't hear it from Nick!