Good to Know

Invader in Your Backyard?

Garlic Mustard
Written by Patti Foley

Garlic mustard is an invasive species and is a threat in Ontario. You can learn to identify this plant and manage it on your property. Ontario’s Invading Species Awareness Program provides the following information:

Impacts of Garlic Mustard

Garlic mustard can invade relatively undisturbed forests. Once established, it can displace native wildflowers like trilliums (Trillium sp) and trout lily (Erythronium americanum). It hinders other plants by interfering with the growth of fungi that bring nutrients to the roots of the plants.

The plant threatens several of Ontario’s species at risk, including American ginseng (Panax quinquefolius), drooping trillium (Trillium flexipes), false rue-anemone (Enemion biternatum), hoary mountain mint (Pycnanthemum incanum), white wood aster (Eurybia divaricata), wild hyacinth (Camassia scilloides) and wood poppy (Stylophorum diphyllum).

How to Identify Garlic Mustard

– Young leaves release a strong garlic odour when crushed.
– First-year plants produce a rosette of dark green, kidney-shaped leaves with scalloped edges.
– Second-year plants grow a stem 0.3 to 1.2 metres high with triangular, alternate, sharply toothed leaves.
– Lower leaves are broad, kidney-shaped and up to 10 centimetres across.
– Upper leaves are triangular and five to 10 centimetres across, narrowing towards the tip.
– Second-year plants produce white flowers with four small petals in May.
– Narrow seed pods 2.5 to six centimetres long split open in mid-summer to reveal tiny black seeds.

Garlic mustard resembles several native Ontario plants. The leaves at the base of the plant look like those of several plants in the carrot family (Thaspium and Zizia), the daisy family (Senecio) and the violet family (Viola). The seed pods look like those of several other mustard (Brassicaceae) species. The easiest way to distinguish garlic mustard from these plant families is to crush the leaves. If they emit a strong garlic smell, then the plant is most likely garlic mustard.

What You Can Do

Learn how to identify garlic mustard and other invasive plants, and how to effectively manage these species on your property. See The Landowner’s Guide to Controlling Invasive Woodland Plants. Go to, click on Here’s a list of things you can do to help fight invasive species, and click on the title.

Avoid using invasive plants in gardens and landscaping. Buy native or non-invasive plants from reputable garden suppliers. Native plants provide habitat and food sources for native wildlife. See Grow Me Instead: Beautiful Non-Invasive Plants for Your Garden. Go to, click on Here’s a list of things you can do to help fight invasive species, and click on the title

Dispose of invasive plants in the garbage. Do not put them in the compost or discard them in natural areas. Discarded flowers may produce seeds.

When hiking, prevent the spread of invasive plants by staying on trails and keeping pets on a leash.

If you find garlic mustard or other invasive species in the wild, please contact the Invading Species Hotline at 1-800-563-7711, or report a sighting online.

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About the author

Patti Foley

Having spent 25 years in Bolton, Patti remains an advocate for Caledon. As a former Regional Councillor and a long-time community volunteer she is passionate about communicating information about its issues, news, events, people, non-profits and businesses.

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