Garlic Mustard – Alliaria petiolata 

What is it? 

Garlic mustard, sometimes called hedge garlic, poor man’s mustard, garlic root, and many other names, is an invasive biennial herb native to Europe. As expected from its name, all parts of this plant give off a distinctive garlic scent. It was introduced to North America during the 1800s as a culinary herb due to its availability in early spring, high nutrient value, particularly in vitamins A & C, and was sometimes planted to control erosion as well. It was used as a medicinal herb for disinfecting wounds, or as a diuretic. While no longer popular, its seeds and chopped leaves can be used as a flavouring for salads and sauces. It has since escaped into the wild and can be found in southeastern Ontario, and parts of Quebec, with smaller populations in British Columbia, Nova Scotia, Prince Edward Island, and New Brunswick. 

Why you should care

Garlic mustard is one of the most aggressive invasive species in Ontario, due to its ability to double the size of its stands every four years and needing only half that to mature. Following their first wintering, surviving garlic mustard stands can produce thousands of seeds per square metre to be spread by people and animals (but not by wind!) that can still grow even 30 years after dispersal. 

Like many other invasive species, garlic mustard can grow in a wide range of habitats, including riverbanks, roadsides, and forest clearings, both sunny and shaded, disturbed and undisturbed. Its ability to grow earlier in the season allows it to outcompete many other native plants through their ability to release chemicals that hinder competitors. garlic mustard can aggressively overtake any available space and soil nutrients leaving little to no room for native plants. Worst of all, despite its nutritious leaves, garlic mustard is rarely a good food source for native fauna and is poisonous to some species like butterflies. As a result, even when removed, it leaves behind a nutritionally starved landscape unable to support salamanders, ground nesting birds, and other small herbivores.   

Unless quickly removed, garlic mustard can take over an ecosystem within 5 – 7 years and weaken its ability to resist other invasive species. This ability to undo decades of conservation work in only a handful of years is what makes it so threatening to the Canadian landscape. Here in Ontario, our famed trilliums are especially at risk because of the spread of garlic mustard, including the drooping trillium (Trillium flexipes). Other wildflowers and plants that are at risk include the eastern false rue-anemone (Enemion biternatum), hoary mountain mint (Pycnanthemum incanum), trout lily (Erythronium americanum), white wood aster (Eurybia divaricate), wild hyacinth (Camassia scilloides), wood poppy (Stylophorum diphyllum), and american ginseng (Panax quinquefolius).  

What can we do?

Although garlic mustard is not a significant source of food to local wildlife, it is also not poisonous or dangerous in any way for humans to handle and can and should be removed wherever you can find it before it spreads too far. 

Those with hobbies in foraging can try their hand at including it in some way in their cuisine if they’re brave enough! However, never consume weeds from public parks without washing to avoid accidentally consuming herbicides. Additionally, avoid young garlic mustard plants, and either cook thoroughly or chop them up to reduce the chances of food poisoning. 

Of course, to help fight back against garlic mustard, readers will first need to know what garlic mustard looks like right?

How to identify Garlic Mustard

Although garlic mustard can be easily identified up close by the garlic smell it releases when any parts are crushed, it can also appear very similar to many other native plants at a distance, like carrots, daisies, violets, and mustards, especially when not in bloom. Before removing any plants that seem like garlic mustard, check for these characteristics to be sure you are really removing garlic mustard.

• Height
  • First year plants can be herb like plants less than 0.3 meters high
  • Mature second year plants can be up to 1.3 meters high
• Stem
  • First year plants look almost like a small bush, with each purplish green stem bearing a leaf, arranged in a basal rosette 
  • Mature second year plants have non-wooded hairy stiff stems emerging from a white taproot smelling of horseradish
• Leaves
  • First year plants have one small (2 – 3 cm) dark green, deep veined leaf per stem, each a circular kidney shape with rounded scalloped teeth, with dozens arranged in a bush like rosette 
  • Second year plants have large (3 – 8 cm) triangular deep veined leaves with jagged teeth arranged in an alternative pattern around the central stem 
  • When crushed, a strong garlic smell is released 
• Flowers
  • Appear only at the top of the stem in small clusters of multiple cross-shaped white flowers, 
  • Bloom in May to early June for second year plants  
• Fruit
  • By mid summer, second year plants can have barren looking branched stems at the top – these are seed pods, 2.5 – 6 cm long, each carrying 10 – 20 small black seeds 

Can you remove Garlic Mustard? 

Absolutely! Many local conservancies, including the Nature Conservancy of Canada (NCC) often host volunteer programs to help remove local infestations of garlic mustard on public land so try applying to your local conservancy to participate on family friendly garlic mustard removal expeditions. Stay on designated trails to avoid picking up stray seeds, and clean clothing and shoes to prevent spreading more garlic mustard. 

Of course, readers are welcome to remove any they find on their own property. Due to its resilient roots, it can be difficult to remove garlic mustard, so infestations have to be found and treated early for easy management. Some environmentally safe techniques include:

• Hand Pulling – most effective in April/May, or September/October, however this can also stimulate the growth or release of seeds. Make sure you’ve pulled up the s-shaped root to prevent resprouting of plants, repeat until the infestation is gone, and follow up with replanting native species in their place
• Mowing/clipping – most effective in early May with second year plants that flowered but have yet to produce seeds. Like hand pulling, mowing or clipping may need to be repeated especially if the root is not removed.
• Disposal
  • Once your garlic mustard crop has been obtained, if you do not intend to consume them, you have to dispose of them safely. Never compost garlic mustard, and always seal your harvest in waste bags tightly in direct sunlight. Flowered plants can still produce seeds, so they should either be dried or burned. 

Consider other ways to prevent garlic mustard from growing in your backyard. Avoid planting garlic mustard and other invasive plants, and buy native plants from reputable suppliers. Always stay on the lookout for this outlaw of a plant!  

If you see any plants that look like the garlic mustard, please contact the Invading Species Hotline at 1-800-563-7711 or the Natural Resources Information Support Centre at 1-800-667-1940 or 1-800-387-7011 to submit your observations! Also consider visiting the EDDMapS Ontario which has partnered with both organizations above to report sightings!

Interested in learning more? See also:

• Nature Conservancy of Canada – Garlic Mustard
• Invasive Species Centre – Garlic Mustard 
• Ontario.ca – Garlic mustard  
• Ontario’s Invading Species Awareness Program – Garlic Mustard – Alliaria petiolata