August 30, 2009 in Features

Invasive plants can take over gardens in a flash

Correspondent
 
SUSAN MULVIHILL Special to photo

The charm of Gooseneck Loosestrife is that they resemble a gaggle of geese. Unfortunately, the plants are quite invasive. Special to
(Full-size photo)

Many years ago, a neighbor gave me some plant starts from her garden. One was a yellow buttercup which she told me can be “a bit invasive.”

I didn’t worry about it back then. That won’t happen in my garden, I thought.

Which brings me to today’s topic: Why do we think a plant with a bad reputation will behave itself in our own garden? Nearly 20 years later, I’m still fighting those buttercups.

There are many perennials that irk gardeners with their invasive habits. I recently asked several of my Master Gardener colleagues which plants they despise and got an earful.

The plant name that came up most frequently was Bishop’s Weed (Aegopodium podagraria). Referred to as a “big nasty” by Maralee Karwoski, this perennial is also called Goutweed.

A member of the carrot family, it thrives no matter what type of soil it’s growing in. Garden books even advise removing its flowers so they can’t reseed.

But as Merilee Dineen reports, “I found the perfect place for it: any narrow bed that is surrounded by cement. It makes a great fluffy border in that situation.”

Jan Baker doesn’t care for Hollyhock Mallow (Malva alcea) one bit. “I’ve been trying to get rid of it forever,” she says.

Baker also takes issue with Globe Thistle (Echinops ritro). “If you let the seed pods drop,” she says, “globes sprout up all over the place.”

One of the plant’s best attributes, however, is that the seeds in those pods are a good food source for Western Goldfinches during the winter.

Dineen enjoys the magenta flowers of Rose Campion (Lychnis coronaria) which are a stunning contrast to their silver foliage, but they can self-seed very easily.

“The only solution is to deadhead, deadhead, deadhead,” she says, referring to the practice of removing flowers that have finished blooming from a plant.

I fell in love with them on a garden tour many years ago. The homeowner gave me a start – just one little plant – while warning me that “it likes to take over.”

After pulling up hundreds of them over the years, I have to admit she was right.

Kay Stoltz feels the groundcover Bugleweed (Ajuga reptans) is another garden thug.

“In my opinion, that should only be planted in hard-to-care-for areas or by those who want a garden but not much work,” she says. “And there is nothing wrong with that.”

It’s important to remember that groundcovers are meant to spread in a garden. For example, I use Sweet Woodruff (Galium odoratum) and Lily of the Valley (Convallaria majalis) beneath my rhododendrons and roses and they look great.

Even though both plants made the thug list, it’s all in the eye of the beholder.

Spotted Dead Nettle (Lamium maculatum) is a member of the dreaded mint family. While you have to give this groundcover credit for its tenacity, remember that if you can’t confine it, don’t plant it.

Another perennial favorite that can be a thug is Lady’s-Mantle (Alchemilla mollis). While I love the way raindrops bead up on the leaves, the plants reseed very easily and will fill a garden bed in no time at all.

Other invasive perennials that made our impromptu list include Shasta Daisy (Chrysanthemum x superbum), Yarrow (Achillea), Bloody Cranesbill (Geranium sanguineum), Evening Primrose (Oenothera), Japanese Anemone (Anemone x hybrida), Snowdrop Anemone (Anemone sylvestris), Creeping Jenny (Lysimachia nummularia), Wormwood “Oriental Limelight” (Artemesia vulgaris), Ornamental Strawberry “Pink Panda” (Fragaria), Gooseneck Loosestrife (Lysimachia clethroides), Catmint (Nepeta) and Violets (Viola spp.).

When it comes to accepting plant starts from other gardeners, Martha Kenney has good advice for all of us.

“Just because it’s free doesn’t mean you should take it,” she advises. “Look to see what it’s doing in the garden of the person who’s offering it to you first.”

And if you decide to take the plant, remember to deadhead, deadhead, deadhead.

Susan Mulvihill can be reached via e-mail at inthegarden@live.com.


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