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Too Much of a Good Thing

Sometimes, You Should Just Say No to Plants
by Jodi DeLong
by Jodi DeLong


Writing about plants and gardening is just one part of Jodi¹s professional writing business. She¹s been a garden columnist for the Atlantic Co-operator for over five years, and last year was invited to do a biweekly column in the Halifax Chronicle Herald, Canada¹s oldest independent daily newspaper. In addition, she writes regular garden features for Saltscapes magazine, Manitoba Co-operator, Grainews, Rural Delivery, and has also had various feature articles in Canadian Gardening, Cottage Life, Complete Canadian Gardener, Aquascapes Lifestyles, and East Coast Gardener. Jodi sits on the National Board of Directors for PWAC, the Periodical Writers Association of Canada, as Atlantic Regional Director, and is also a member of the Writers Federation of Nova Scotia. When she¹s not writing, she¹s gardening, reading about gardening, photographing gardens, thinking about gardening, or ignoring the housework.

August 22, 2010

In a perfect gardening world, plants would settle politely into their planned sites in the garden, grow to their proscribed height and width, flower like dandelions all season, and be oblivious to disease and pests.

As we all know all too well, they don’t behave quite like that.

Some are overachievers, space invaders of the worst sort. That pretty ground cover you saw around a maple at your friend’s house and brought home is now planning to take over the world. The freely seeding annual that has dispensed seventeen million seedlings isn’t so appealing now.

Take goutweed, for example, Aegopodium podegraria. Yes, please take it, far, far away from me. This plant shouldn’t be sold at garden centres or nurseries, at least without warning labels, but it is. And anyone who has heard my rants about goutweed and who has the stuff in their yard, nods sympathetically. It’s one of those plants that spreads by underground stems, or rhizomes, and trying to get rid of it is like trying to discourage telemarketers: you succeed with one, and seventeen more get your number. If you don’t get every single little root and stem and tendril of goutweed, it will be back with a vengeance.

Most gardeners have their own particular horror story about some lovely plant that looked wonderful in another person’s garden, but which went rampant when they brought it to their own plantings. And by the same token, what might be overwhelming in a small city garden can work just fine in a large perennial border or as a ground cover. The trick is to be aware of those space invader types of plants, and to exercise a few precautions when using them.

Except for goutweed. Just don’t plant it at all.

In many cases, plants that have become nuisances are species that were once grown as ornamentals but escaped the confines of a garden to become persistent throughout an area. One of the most annoying is a type of bellflower sometimes commonly called bluebells, Campanula rapunculoides. This plant spreads voraciously by rhizomes, and is easily recognized for its stalks of nodding, purple, bell-shaped flowers. We’ve also all heard about and seen purple loosestrife, Lythrum salicaria, which is very invasive in wetlands and along waterways and which started life as an ornamental plant.

Some plants to watch out for include anything that has the word ‘weed’ in its name, such as bugleweed, a groundcover which spreads by rhizomes, or butterfly weed, (Asclepias) which have a tendency to seed profusely.

If you opt for something that is labeled as a ground cover, be aware that it will do just that: cover ground. A lot of it. This can work well if you are wanting to plant something to fill in a hard-to-mow or high traffic area, but can be overwhelming in a small garden space.

If the variety you have is a variegated type, chances are it won’t be as invasive as the regular, green-foliaged type. Variegated plants have less chlorophyll in their leaves and thus are often a bit less hardy than their all-green relatives. We have a variegated obedient plant which is very well behaved, far more so than its all-green kin.

With some plants that spread by rhizomes, you can plant them within a root barrier that keeps them within a certain confined area. You can also plant spreading plants in pots and sink those into the garden, or plant them in a dedicated raised bed. For example, we’re partial to Japanese lanterns, (Physalis alkekengi) those lovely orange podded perennials of the fall, but have them planted in their own raised bed beside the barn.

In the case of plants that self-seed, mulching your garden heavily will usually deter all but the most inspired of seedlings. Personally, I love the volunteer seedlings that pop up in our gardens; the nigella, larkspur, poppies, calendula, sunflowers, forget-me-nots and others that repopulate in interesting places. I’ve learned to mulch very heavily around the teasels we grow for their architectural interest, and for the seeds that appeal to birds, because teasels have an inspired taproot and prickly foliage and can be miserable to try to dig out once they get some size. If you’re concerned about an overabundance of seedlings, cut the flowers off those heavy seeders once they’ve finished flowering.

But whatever you do, don’t plant goutweed. Or if you do, don’t say you weren’t warned.

Some overachievers to avoid or to grow with caution.

I’ve given the most common name as well as the botanical name, to avoid confusion.

Spread by rhizomes:

Gooseneck Loosestrife: (Lysimachia clethroides)
Groundcovers such as goldmoss stonecrop (Sedum acre), periwinkle (Vinca major), bugleweeds, (Ajuga species) snow-in-summer (Cerastium),
Japanese knotweed : (Polygonum cuspidatum)
Jerusalem artichoke : (Helianthus tuberosus)
Tawny daylily, ditch lily: (Hemerocallis fulva)
Obedient plant: (Physostegia virginiana)
Korean bellflower: (Campanula takesimana)
Many of the mints (Mentha species)
Comfrey (Symphytum spp.)

Profuse Self-seeders

White Valerian: (Valeriana officinale)
Plume Poppy : (Macleaya spp.)
Meadow cranesbill (Geranium pratense)
Teasel (Dipsacus sylvestris)
Scotch Thistle (Onopordum acanthium)

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