Lise’s article last week caused me to start thinking about dangerous plants, plants that entice you, only to run amok once you have offered them an invitation into your garden. Just as there are some attractive people who are disastrous dinner guests, there are some beautiful plants gardeners should avoid like the plague.
The first on my list is Clematis paniculata, also known as Clematis terniflora and ‘Sweet Autumn’ Clematis. This clematis has everything going for it: profuse blooms that are fragrant, rapid growth so it makes a statement quickly, and lovely seed heads in the fall—and that is the problem.
The seed heads disperse thousands of seeds everywhere: Soon not only you but also the whole neighborhood will be supporting this clematis. Only plant it if you dislike your neighbors and love digging out seedlings. Try our native Clematis virginiana instead. It too has small white flowers that have a slight fragrance and grows to be a large vine. It isn’t as showy as the Japanese C. paniculata—but you won’t be swamped with seedlings.
The problem I have with groundcovers is precisely that: They cover ground. Think hard before you plant the next three plants, because once they begin their march it is hard to stop them. I find that I like the idea of groundcovers much better than I do when facing them in reality.
I once planted some creeping sedums in my perennial border, thinking they would cover up the mulch and hopefully work their way around the plants: What was I thinking? I planted three specimens in my rich soil and watched as they took off. Sedums keep out the weeds as they form a thick mat, grow well in poor soil, never need watering unless you live in the Sahara Desert, and spread quickly. They are wonderful in rock gardens where they are somewhat contained by rocks and the lack of soil. Plant them in good soil and you have a groundcover that mows down everything in its sight. They look so innocent until you drop the reins.
Lise profiled Liriope spicata, the liriope that gallops. The one you want is Liriope muscari that forms lovely clumps. Despite its galloping habit, L. spicata is rather sparse looking whereas L. muscari makes a spectacular border if you plant the clumps close together.
I planted Euphorbia robbiae because I didn’t know any better and was desperate for plants the deer would leave alone. This attractive—for a Euphorbia—groundcover is dangerous. It covers anything and everything, which is fine if you’re covering a junk heap, but is disastrous if you have reasonably good soil. Its stoloniferous nature ensures that it will pop up where you least want it.
Helleborus x hybridus is truly a seeding monster in my yard—and unlike Helleborus feotidus that also seeds—it’s very difficult to pull out. Hellebores have so much going for them: They’re poisonous so deer leave them alone, they flower early, letting us know that there really will be a spring, and once trimmed, they make tidy clumps.
However, each carpel will soon swell obscenely with seeds, seeds that it’s anxious to disperse. Fortunately the seeds are heavy enough that they won’t fly around the garden but, instead, will settle at the feet of its parent. Soon you will have a mass of hellebores that no longer have room to make those attractive clumps you remember so fondly. And the worst part? The deer don’t eat them. They have no natural predator. Try giving them away: No one wants more hellebores. The only solution is to cut off the flowers before the carpels pop open, leaving you to wonder why you bother to even grow them.
Every gardener learns through trial and error but there are words in plant descriptions that you should quickly perceive as warning signs: “exuberant,” “a quick grower,” “stoloniferous,” and “seedy” are but a few words of warning. Learning to read these cautionary signs will save you hours bent over pulling out unwanted specimens.
Lise Jenkins and Kit Flynn are contributing columnists. Absent from their gardens, they enjoy roaming our region exploring the intersection of innovation and horticulture. More on Twitter @AbsenteGardener or email: firstname.lastname@example.org.