Garlic Mustard
(Alliaria petiolata)
Overview
Brought to North America by early colonists, this invasive plant is now spreading across the continent at a rate of 6,400 square kilometres per year. The success of garlic mustard is multi-faceted. Aside from having no natural predators in North America, its low palatability and toxic cyanide production make it an unfavourable choice for most native herbivores.
Garlic mustard grows in a wide rrange of habitats and can often be found in Ontario’s temperate forests, agricultural fencerows, public right of ways and residential lands. While it will invade most disturbed sites, it can also spread into undisturbed habitats, including mature forest floors.
Main Threats
Unlike most invasive plant species, garlic mustard does not appear to require disturbance to become established, making it a threat to mature forests. It is allelopathic, as the roots produce chemicals that have been shown to prevent growth of other plants, with effects lasting for years after the garlic mustard has been removed.
Forest Floors, Wildflowers, and Garlic Mustard
A range of stunning wildflowers can be found on the Bruce Peninsula, including a variety of rare orchid species. Many of these wildflowers are found underneath the canopy of mature forests. Garlic mustard is able to establish on undisturbed forest floors, crowding out and displacing native flora, wildflowers included. Stopping the spread of garlic mustard on the Bruce Peninsula is of critical importance to protect the habitat of local flora. Learn more about the stunning orchids of the Bruce Peninsula in the Bruce Trail Magazine.
Identification
Photo: Nature Conservancy of Canada
Leaves (Year 1)
Garlic Mustard is a biennial plant, which means it has a two year life cycle and looks distinctively different in year one vs. year two. In the first year, garlic mustard forms a rosette of kidney-shaped leaves that hug the ground.
Photo: David Cappaert, MSU
Leaves (Year 2)
The following year, garlic mustard grows up to one metre tall. The green leaves are heart-shaped with toothed edges, and have a garlicky odour when crushed.
Photo: Ken Towle
Flower (Year 2)
In year two, garlic mustard grows one or more flowering stalks. The flower is small with four leaves, and is white in colour.
Additional Resources:
The following links provide additional information on garlic mustard, including negative impacts, identification features, and methods of removal.
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