Garlic Mustard

Garlic Mustard is a non-native herb. It is a strong, invasive competitor with the ability to grow in low light conditions, produce many seeds, and spread rapidly. It thrives in both disturbed and undisturbed areas, and can become the dominant forest groundcover within five to seven years of being introduced to an area. It is also common to find this invasive species in your own garden.

How Does Garlic Mustard Impact and Invade an Area?

  • Garlic Mustard reduces forest ecosystem biodiversity;
  • It begins growing in early spring and gets a head start on other flowering plants and tree seedlings;
  • It takes resources away from native spring woodland plants such as Spring Beauty, White Trillium, Trout Lily, Sweet Cicely, and many others; 
  • Garlic Mustard appears to reduce habitat quality for several species of salamanders and molluscs by changing the composition and depth of the plants that decompose on the forest floor, which these species rely on; 
  • Garlic Mustard changes the soil and impacts important natural associations between plants and fungi by destroying the fungi; 
  • Insect communities are also impacted by its presence; 
  • Deer do not eat it, but will still graze on the remaining native plants (as is natural) and contribute to the spread of Garlic Mustard by disturbing the soil and carrying seeds from one location to another;
  • Seeds can remain alive in the soil for five years or more; 
  • Seeds sprout quickly in disturbed soil; disturbing soil that has Garlic Mustard seeds in it will cause more seeds to sprout;
  • Roads and trails are prime passageways for Garlic Mustard invasion; transportation corridors, trails, parking areas, and recreation sites are known areas of early infestation;
  • Further distribution is mostly by humans, pets, and other animals that accidentally carry seeds in shoe treads, or bike treads, or paws;
  • Populations spread an average of 6,400 square kilometres per year in North America! 

Appearance and Growth

  • It is a cool-season plant with a two-year growth cycle; first-year plants appear only as a cluster of green leaves close to the ground. Clusters remain green through the winter and develop into flowering plants the following spring;
  • Its leaves, which radiate from a main stem, are coarsely toothed and triangular to heart shaped; when crushed, particularly when new, the leaves give off an odour of garlic; 
  • Flowering plants of Garlic Mustard reach from 0.6 to 1 metre in height and produce button-like clusters of small white flowers, each with four petals in the shape of a cross;
  • Beginning in May, tiny seeds are produced in erect, slender pods, and become shiny black when mature; when mature, the capsules burst open and can throw seeds several metres;
  • In dense woodland stands, seed production can range from 9,500 to over 100,000 seeds per square metre per year. 

Control and Removal 

  • The best approach is to limit the spread of garlic mustard in the first place; 
  • Awareness is key so help to spread the word about this invasive species;
  • Restrain pets in invaded areas, and brush off any bits of mud or vegetation from clothing, boots, and paws before leaving infested areas;
  • Never buy this plant at a nursery or plant it in your garden; 
  • Join an organized team to help remove this plant; the Biodiversity Education and Awareness Network advises against removing this plant on your own (except from your own yard);
  • On International Biodiversity Day, May 22, approved groups follow strict protocols to be sure they are removing and disposing the right plants and in the right manner to control and eliminate the spread of Garlic Mustard;
  • There are a number of approaches to removal and control, including cutting, pulling, and mulching Garlic Mustard, and planting native species;
  • In controlled situations, experts may use fire or herbicides;
  • Visit the Ontario Invasive Plant Council’s website for more information on control and removal of this and other invasive plants found in Ontario.