Invasive Garlic Mustard: Be on the Lookout
Virginia Battiste
With the proclamation of the new Alberta Weed Control Act on June 16, 2010, the world of gardening in Alberta has shifted and changed.
Many of the newly declared "prohibited noxious weeds" are familiar to gardeners as attractive ornamentals. Unfortunately, those plants now included on the Prohibited Noxious list must be removed from your garden and disposed of safely, to ensure they do not spread to other locations. Vigilance in eliminating known invasive plants, and being on the lookout for newly declared invasives in natural areas, are keys to keeping ahead of the potential damage such plants can cause. (visit <www.invasiveplants.ab.ca> for more information and see the May 2010 issue of Gardener's Gate or check out this list.).
Recently, to the surprise of weed management professionals, a plant that was just declared Prohibited Noxious in the new Act was found in two forested areas in Edmonton and St. Albert. Included in the new Act as a precaution, because it is known to be highly invasive in forested areas in Ontario and the Northeastern US, garlic mustard was not known to be present in Alberta prior to the discovery of the two plots earlier this spring.
Within a decade in Wisconsin, the forest floor in forest after forest had been taken over by garlic mustard, to the exclusion of all other forbs (herbaceous flowering plants) and some woody species. It can also out-compete tree seedlings. The problem is that takeover by garlic mustard inevitably leads to a secondary invasion of forests by unwanted woody invasives like European buckthorn, already known to exist in the Edmonton area. This latter invasion will be worse than the former.
Garlic mustard is semi-evergreen to evergreen. Its rosettes, formed during the first year, will appear as a bright green carpet after the snow has gone in late winter. Old, dead plants can stand .5 to .75 metres tall and look very much like dead mustard plants, except that they are found in the middle of a forest area.
A biennial herb used by some as a substitute for garlic, there are two telltale characteristics that identify the plant. A member of the mustard family, garlic mustard has a cross-shaped, four-petalled white flower and when the leaves are crushed they smell like garlic. If those two things are present, you are dealing with garlic mustard.
This plant can be controlled by pulling or by use of low impact herbicides. However, the seed remains viable for five years, so there is a need for repeated pulls of plants throughout the growing season, and annual monitoring is necessary.
If you find anything that looks like garlic mustard, report it immediately to your local weed management authorities.
For more information:
- Garlic Mustard Damage to Forest Floor <www.in-sitevideo.com/wff/garlicmustard.html>
- AIPC Fact Sheet–Garlic Mustard: <www.invasiveplants.ab.ca/downloads/FS-GarlicMustard.pdf >
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(Virginia Battiste is the Administrative Coordinator for the Alberta Invasive Plants Council. Originally published in the Gardener's Gate, August 2010.)