As a lifelong gardener based in New England, my personal list of banned flora is expansive and begins with bugleweed (Ajuga reptans). Although some cultivars are said to be less energetic, the species has taken over my property.
Also high on my “not in my garden” list is gooseneck loosestrife (Lysimachia clethroides), a temptingly pretty plant with arching flower spires that overruns everything else. Creeping Jenny (Lysimachia nummularia), from the same family, covers the ground with a thick mat of round leaves that nothing can penetrate. English ivy is another rambler (with tenacious suction cup-like roots along its branches). I’ve also had run-ins with tansy, tradescantia, cypress spurge (Euphorbia cyparissias) and Anemone canadensis, to mention only a handful.
Identifying unfit plants might require some research and observation. Labels are not apt to say “does not play well with others” or “adopt at your own risk” or “prepare to spend the rest of your life engaged in hand-to-hand combat.” Trusted garden centers, nurseries, fellow gardeners and professionals can offer advice. I suggest researching unfamiliar plants before installing them in your garden, especially where space is limited.
It’s worth noting, though, the United States is a big country and plants that pose problems in one region could be fine in other areas. And remember: Even these aggressive plants can be tamed, in the right hands. Garden designers with plenty of experience with soils and plant habits might use them in places where they need to cover large expanses of ground, or where the plants can compete with other aggressive species.
I asked several garden designers to share their most unwanted lists with me, including Richard Hartlage of Land Morphology in Seattle; garden designer Donald Pell in Pennsylvania; and Edwina von Gal, a garden designer based on Long Island as well as founder and board chair of the Perfect Earth Project. Hartlage suggested a general test of a plant’s aggressiveness. “If your neighbor has lots and lots of divisions to share, maybe you don’t want that plant,” he says.
Mints are frequent offenders, and they top many gardeners’ lists of undesirables. In particular, spearmint and peppermint are energetic, persistent spreaders when planted in a landscape, but apple mint and other varieties can also go rogue. “Use those mints as container plants,” suggests Hartlage, “but don’t put them in the ground.”
Plenty of landscapers also avoid plume poppy (Macleaya cordata). “It’s a beautiful plant, but way too much trouble,” von Gal says of this tall perennial with glovelike foliage, which was popular in historic landscapes and can lie dormant for decades. Canada goldenrod (Solidago canadensis) also knows no bounds. “That plant just wants to take over,” says Pell. Other goldenrods, however, might be more appropriate for gardens.
Mints, plume poppies and goldenrods increase primarily by sending wandering runners (rhizomes) to expand their territory, a common multiplication method for overly energetic plants.
Ornamental grasses, on the other hand, often use seed dispersal to expand. Silver grass (Miscanthus sinensis), which is on invasive lists in many states but still frequently sold in nurseries, is a classic example of a grass that doesn’t work well in gardens because of its rapid growth via seeds. Hartlage also finds that Mexican feather grass (Nassella tenuissima) can spread quickly by seed in warm zones (but self-seeding might not be an issue where this grass is not hardy).
I also have found that morning glories can be a nightmare because of overly prolific seed sowing. Although “Heavenly Blue” (Ipomoea tricolor) has never self-seeded in my New England garden, other morning glory varieties continue to pop up annually. I’ve learned to identify the seedlings and remove them before they begin another generation.
I could continue to call out inappropriate garden plants; the list is lengthy. A wise strategy would be to monitor new plants in the garden. If something begins to overstep its bounds, curb it swiftly. Pulling aggressive plants early is better than taking a wait-and-see approach. And do not make the mistake of sending aggressive plants to your compost pile, where they can continue to multiply.
Then, share your experiences with fellow gardeners. Spread the word, rather than the plants.
Tovah Martin is a gardener and freelance writer in Connecticut. Find her online at tovahmartin.com.
