If a plant's label claims it 'grows aggressively,' you may want to avoid it altogether. Here are some plants that don't play well with others.
On my to-do list this weekend at my house in upstate New York is the usual overload of springtime garden chores. I plan to clean out the matted messes of leaves under shrubs that I never got to last fall, finish clipping the dead tops of perennials I ignored in November and start spreading weed-smothering mulch.
But there's another task I wish I didn't have to face: Ripping out or thinning the fast-spreading plants that have become permanent headaches in my gardens.
I'm not talking about kudzu or Japanese knotweed, those notoriously rampant growers whose sale is banned in many states. I mean plants that are sold at garden centers and online often without any kind of warning that they could take over your yard.
Some of these plants expand through fast-growing roots or underground stems called rhizomes. Others spew hundreds of tiny seeds each year, creating offspring where you don't want them.
There's an ongoing debate in the garden world over which plants should be considered invasive and taken out of circulation — some experts say even old favorites such as rose of Sharon and grape hyacinth are dangerous — and which are simply vigorous growers. But all of my problem perennials can be thugs, shoving aside better-behaved plants that get in their way.
Lamiastrum 'Herman's Pride'
Chief among my horticultural hooligans is a vine called Lamiastrum "Herman's Pride." Its spiky silver leaves are overlaid with intricate green veins and it produces handsome yellow flowers in spring. Not only is it an eye-catcher but it has the rare ability to thrive in dry shade, the toughest garden condition. And deer hate it.
So what's not to like?
I put a bunch of Herman's Pride on a hillside under dense trees, where many things struggle to grow. Not this plant. Within two years it had multiplied like those puffy tribbles on "Star Trek." Its roots and vines wormed their way into the stalks of nearby daffodils, tried to take my hostas hostage and even escaped over a stone wall into the lawn.
Last summer I decided it was curtains for Herman. I ripped all of it out. Or at least I tried to. Capt. Kirk would appreciate this plant's ability to reproduce itself from the smallest piece of root.
This spring Herman's shiny leaves are taunting me again by poking out of the ground ahead of almost every other perennial. Maybe that's why one of its nicknames is Archangel.
Here's my list of other plants you should think twice about putting in your yard. Fellow weekend gardeners will want to expend their limited free time on perennials with better manners:
Bishop's weed: Like lamiastrum, this attractive green-and-white plant multiples in dry shade, an indicator of how tough it is. I somehow ended up with a few sprouts of bishop's weed (Aegopodium podagraria "Variegatum") in my garden, which likely tagged along when I was given some plants from a friend's yard. Two summers later these bishops threatened to take over a big swath of the flower bed. Was it the start of a holy war?
Last year, I tore out the bishop's weed at the same time I tried to dispatch Herman's Pride. But my triumph was short-lived. Last weekend I saw sprigs of bishop's weed peeking out of the soil in my hillside garden.
My advice: Don't ever plant either bishop's weed or Herman's Pride unless you want it to fill an entire area that is well separated from other garden beds.
Rudbeckia triloba: This tall flowering plant, one of several commonly known as brown-eyed Susans, puts up a profusion of yellow blooms with brown centers in late summer. For several years I thought it was a great way to have color in my yard after many other flowers had faded.
But this variety of rudbeckia — not to be confused with the popular and well-behaved Rudbeckia "Goldsturm" — seeds itself so freely that each spring I have to yank out dozens of the youngsters that show up in the strangest places.
Some of the offspring pop up in the middle of other plants, making them tough to extract. Others appear across the yard in another flower bed. And when I transplanted some phlox from one bed to another, Rudbeckia triloba hitchhiked along. If you don't catch the young plants soon enough they develop an enormous root structure that is tough to dig out.
My verdict: Avoid it unless you use it in a meadow or naturalized garden, or are willing to snip off all the spent flowers each fall before they turn to seed.
Sweet woodruff: This low-growing ground cover (Galium odoratum) produces sweet-smelling white flowers atop its whorled leaves in spring that perfume the garden. But it spreads by its root stems into a thick mat and its tentacles pop up inside other nearby plants.
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While not as rampant a spreader as Herman's Pride, sweet woodruff can be annoying. I moved most of mine to a more-open area after it began to worm its way into nearby foamflowers (Tiarella) and lady's mantle (Alchemilla).
Sundrops: I decided I had to have this plant (Oenothera tetragona) after I saw its bright yellow flowers filling the base of a restaurant sign in my town in late spring, after the daffodils were gone and little else was blooming. It turns out the key fact is "filling."
Sundrops have an amazing ability to replicate all over the place, including between the clumps of iris I planted nearby. While they are easy to pull out before they get too big, if you don't catch them early their roots can become entwined with those of other plants.
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Bee balm: Bee balm (Monarda didyma) is another major-league spreader. While I love its elaborate flowers, which resemble a headdress or royal crown, and the bees and butterflies appreciate the nectar, this native plant can quickly smother everything around it by forming a thick mat.
I've successfully kept it in check for years in one of my gardens by surrounding it with flat rocks. But in another garden where I didn't take this precaution, the bee balm expanded and seems to have killed some lily bulbs beneath it that I really liked. I've also heard about keeping bee balm in check by planting it in a large container and sinking the container in the garden, but that's one more garden chore I never got around to.
Dame's rocket: While not commonly sold as a plant in garden centers, the seeds of dame's rocket (Hesperis matronalis) are promoted as a wildflower, though technically it is an introduced species from Eurasia. Where I garden in upstate New York, the fragrant pink and white flowers break out along roadsides in early summer. Thinking it would look just as great in my yard I dug up a clump.
Big mistake. Dame's rocket throws off zillions of seeds each year. After a season or two of ripping out its young while keeping the mother plant, I decided it was better to remove all of it. So far, that seems to have done the trick.
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Artemisia 'Oriental Limelight'
Artemisia: While some varieties of this frilly-leafed plant play well with others, I made the mistake of planting Artemisia "Oriental Limelight." It spreads by both its aggressive roots and abundant seeds. Sure, its yellow-splotched green leaves light up the garden, but it threatens to take over the entire bed.
A year after I planted Oriental Limelight, a big plant-marketing concern that sells it, Proven Winners, changed its tag to warn that it "may be aggressive or even invasive" and that it could be used in pots or containers "but not in the landscape."
I've been tearing out my Oriental Limelight this spring in the hopes of confining it to a small patch, but I'm not optimistic. I've read accounts of gardeners resorting to the kill-all herbicide Roundup but still being unable to eradicate it.
The bottom line: Be careful about planting anything whose label says it grows aggressively. Either avoid it entirely, or place it in a confined area to see how fast it spreads.