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Invasives in The Islands: Garlic Mustard

By September 4, 2020 No Comments

Vibrant green with an appetizing smell, garlic mustard is an invasive plant that is rapidly spreading across Ontario.

Originally introduced to North America in the 1800s from Europe for medicinal and edible purposes, Garlic Mustard has since become a nuisance. First year plants grow in single heart-shaped rosettes with toothy edges. Second year plants grow taller, from one to four feet, with more triangular toothy leaves and small white flowers with four petals in the spring. As previously mentioned, one of the easiest ways to positively identify garlic mustard is by smell. When crushed any part of the plant, but especially the leaves, should have a strong garlic odour.

One of the main issues with garlic mustard is that is can spread incredibly quickly and the species is highly shade tolerant and therefore flourishes in wooded settings, shading out native understory as it spreads. Additionally, garlic mustard uses allelopathic compounds which are a tool used by the plant to suppress other surrounding plants. It releases biochemicals through its roots which in turn discourages or entirely prevents the growth of plants in the vicinity. To add to this proficient spreading mechanism, a dense stand can produce over 60,000 seeds per square metre, further increasing the potential for spread. Important and already threatened species such as drooping trillium and American ginseng are negatively impacted by the existence of garlic mustard in Ontario forests.

A rabbit amongst first year garlic mustard, characterized by toothy heart-shaped rosettes. Photo Credit: Sue Sweeney / CC BY (https://creativecommons.org/licenses/by/4.0)
Second year plant with more triangular leaves and small white flowers. Photo Credit: Robert Flogaus-Faust / CC BY (https://creativecommons.org/licenses/by/4.0)
A benefit of pulling this invasive is that it is an edible plant so the leaves can be put in a salad for dinner!

One of the most effective removal strategies for garlic mustard is simply pulling it out. The removal of large stands can become more complicated, and therefore large tarps can be used to cover and eliminate the plants. Planting taller subsidiary species to completely shade out and discourage growth of first year rosette plants is also a potential solution. As with any invasive plant, garlic mustard should be disposed of in the garbage in tightly sealed plastic bags to prevent further spread.

– By Emily Kutchaw, Agricultural Property Manager
To learn more about garlic mustard, or to get involved in invasive species removal with TIWLT, send us an email at info@tiwlt.ca.
References
McCallum, J. (2020, June 25). Understanding Ontario’s native, invasive, and aggressive plants. Retrieved August 10, 2020, from https://www.greenup.on.ca/understanding-ontarios-native-invasive-and-aggressive-plants/
Ministry of Natural Resources and Forestry. (2018, October 22). Garlic Mustard. Retrieved August 10, 2020, from https://www.ontario.ca/page/garlic-mustard
University of Georgia. (n.d.). Garlic Mustard, Alliaria petiolata Capparales: Brassicaceae. Retrieved August 10, 2020, from https://www.eddmaps.org/species/subject.cfm?sub=3005