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THINK TWICE BEFORE PLANTING THESE ‘THUGS’
More than once I have marveled from my car window at the beauty of a stand of flowers. I’ve often been tempted to take a closer look, identify the plants, and maybe dig out a clump or grab a handful of seeds for transplanting back home.
I have learned the hard way that not every flower growing in the wild or in someone’s back yard belongs in my garden. Some perennial flowers have growing or spreading habits that make them unsuitable for the well-mannered garden.
A few weeks ago Minnesota gardeners sounded off on “thug perennials” that “should come with a warning that they will take over your garden as soon as your back is turned.” Dozens of gardeners offered email suggestions on plants that deserve to be categorized as thugs. Be careful -- and perhaps do some additional research -- before you introduce any of these rascals into your garden. (Quoted remarks are excerpted from listserv discussion.)
Gooseneck loosestrife. “It's too pretty not to have in the garden, so I have it surrounded by lawn edging. Even so, I have to periodically beat it back with axe and spade.”
Obedient plant (Physostegia virginiana). “As an experiment, I planted large patches of three invasive perennials next to each other, to see which would dominate. The three were bee balm (Monarda didyma), giant catmint (Nepeta siberica) and obedient plant. In a few years the obedient plant had won handily, overrunning and almost eradicating the other two and everything else in its path.”
Lily of the valley. “It’s a great plant for dense shade but we all know how difficult it is to confine.” Another gardener wrote: “Anybody who plants lily of the valley and wants it to stay in one place really should surround it with a shield that is sunk at least six inches into the soil.”
Tansy and yarrow. “Two of the worst I’ve encountered are tansy and the common white form of yarrow. Although the yarrow runners aren’t too deep, they form a dense mat in no time. Tansy’s runners go really deep and really far...never again!”
Violets. “I have something of a love/hate relationship with violets. I have some beautiful white ones that grow in my back garden. Early in the growing year they are so beautiful. Later, they get leggy and spread like crazy. They are always a welcome sight in the spring but as the season progresses I pull them out by the handful.”
A Ramsey County gardener offered these thoughts on two “thugs” in the shade garden: downy yellow violet (Viola pubescens) and Virginia waterleaf (Hydrphyllum virginianum). “A friend gave me bits of both years ago and I'm still trying to get rid of them. They self-seed everywhere and come up in the middle of other perennials. Every spring I dig out every one I can find, but the next year they're back again. In his book, Wildflowers of Minnesota, Stan Tekiela says the downy yellow violet has a seed capsule that acts like a shotgun, shooting seeds in all directions. Right on.”
Loosetrife. “The most invasive plant I ever planted is Lysimachia ciliate ‘Firecracker.’ Those lovely purple leaves are such a great contrast to all the other green ones. However, runners took off everywhere within minutes of planting. I see this plant at plant swaps and really think it should come with a warning!”
Another gardener added this about the same plant: “The foliage is a lovely color and the little yellow flowers are charming. However, the offspring of my first plant spread eight feet from the parent. It has the unpleasant habit of sending up single plants, rather than big clumps, that hide in other perennials. After being unable to eradicate it by digging it up -- the tiniest bit of root left behind results in a new plant -- I used Roundup and had to apply it twice to be effective. I still have a fairly large clump of it left because it is such a nice maroon accent in the green perennials. However, this spring I will get out the Roundup first thing to nuke the babies. It really will take over the garden.”
Crown Vetch. “It’s the thug of all thugs. Years ago, I admired it in a friend’s garden...such delicate leaves, such lovely pea-like blossoms! I bought three plants for 99 cents. It took over my perennial bed and choked everything out. The roots are thick and have to be chopped out with a mattock. I have sprayed it with Round Up for two years and it still survives. Garden centers should put a warning sign on it.”
Gardeners mentioned a few other thugs but the ones listed here were the most discussed. Carol, a gardener from western Minnesota, summed up the thugs discussion nicely, as follows: “Thugs are like weeds in that they are simply plants in the wrong places. Some of those listed have made it into my gardens in places where they are managed well and do their thing without becoming world-dominance addicts. I've always felt that all of life's lessons are contained in the plants and dreams of our back yards. Thugs are just part of that story.”
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