Browse the shelves of most nurseries across the country and, sadly, you'll find goutweed. Much touted for its ability to thrive in areas where little else will set foot, goutweed is considered by many as the ultimate low-maintenance ground cover for shade or part-shade. That's because, once established, this low-growing perennial with its all-green or variegated foliage spreads without any encouragement, much less nurturing, coddling or fussing. And therein lies its appeal. Goutweed rewards time-stressed homeowners with verdant borders and beds worthy of the best green thumbs without lifting a finger.
The low-maintenance promise is ironic, says Danielle Tassie of the Ontario Invasive Plant Council (OIPC), because "goutweed completely takes over your garden and you're left with a big maintenance issue."
Once planted, goutweed, under any of its aliases, including bishop's weed and snow on the mountain, will be just about the only plant you grow. "Once it gets going, says Tassie, "it can out-compete tree seedlings." Insidiously spreading by rhizomes, a massive system of underground roots, goutweed knows no bounds, including fences, which means that once it's in your yard, it's in your neighbour's too.
Eradicating goutweed takes time, and it's backbreaking work. There are two methods, says Tassie. The first is to dig it out. "You need to get the entire root," she explains, "without leaving any bits behind." And because that's easier said than done, remnant roots soon sprout, creating more plants that need to be dug out. "Do this for four or five years," says Tassie, to control the spread.
Gardeners have reported some success with a second method, says Tassie, and that is to remove or starve the leaves. Mow them down in the spring or cover the plants with a dark tarpaulin to prevent light from reaching the foliage.
"Monitoring is important," she says, "and so is working with your neighbours." Be diligent about rooting out plants. "And remove any flowers before they go to seed" to prevent seedlings from taking hold and multiplying the problem.
The best way to keep goutweed out of your garden is to grow better-behaved look-alikes. Plants that do the same job include the glossy-leafed European wild ginger (Asarum europaeum), elegant but tough-as-nails barrenwort (Epimedium spp. and cvs.) and the pink-flowering big-root geranium (Geranium macrorrhizum).