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Allan designs and plants flowering gardens in Montreal, Zone 5 [USDA Zone 4] .

See website, design work and favorite flowering plants at  gardengurumontreal.ca

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Entries in Epimedium (1)

Sunday
Feb142010

Smothering Aegopodium, an Unwelcome Perennial

A ritual takes place in many shaded gardens around the world. It begins with homeowners frustrated that nothing beautiful will grow in their sunless gardens. Inquiries and suggestions ultimately lead them to plant Aegopodium. This groundcover, aka Goutweed, grows in the shade and thrives wherever most other plants cannot survive. To the unsuspecting homeowner, it is an attractive perennial with eye-catching leaves. One variety has foliage, beautifully variegated in green and white, which illuminates shady spots. However, to the seasoned gardener, the plant is a monster.

Several years will pass and the Aegopodium will have spread far beyond its intended location. Homeowners will attempt to lift it out without success. They will bury it with more soil, but it will manage to percolate upwards. After a few years of trying to get rid of it, frustrated homeowners will look for advice, once again.

Removing Aegopodium requires strategy because it cannot be eliminated by lifting. Its roots are too stubborn and too pervasive to respond to manual or mechanical solutions. Glysophate, a systemic herbicide sold under several brand names such as Round Up or Wipe Out, is needed to kill this plant. Alternatively, it may be smothered by covering the plant with an industrial strength semi-permeable membrane called geotextile.This sheeting is then camouflaged with anywhere from one to two feet of earth, or mulch. Earth is more effective because it is heavy enough to keep the membrane in place. The operative word here is industrial strength; consumer grade membrane is not strong enough to fight Agepodium. 

To replace the about-to-be smothered groundcover, select appropriate shade loving plants and insert their root balls beneath the geotextile. Simply slash at the geotex with a very sharp blade to expose the earth below, dig a hole for the plant, insert plant, back-fill with earth, replace the geotex and camouflage with earth. The semi permeable textile will allow water to seep through to nourish the roots growing beneath but will not permit plants, targeted for smothering, to grow up through it. If the homeowner needs a replacement ground cover, consider planting Epimedium, which is availble in both green and variegated cultivars. While it does spread, the growth is controllable. Experiment by planting it in the earth above the geotex.

The landscapers that work in my neighborhood have been attacking Aegopodium for over thirty years. They have decided that smothering with a strong membrane is the only safe solution. In years past, they might have considered using herbicide. Today that is no longer an option. Some of them have lost a colleague to fatal diseases that have been linked to exposure to toxic substances. Now, they refuse to touch even those products, like Glysophate, that are advertised as safe. Local governments, that have already banished other toxic herbicides, are slowly introducing legislation to banish this one, as well. I suppose that landscapers already know what we are about to learn.