What is it?
Garlic mustard (Alliaria petiolata) belongs to the mustard family. Also known as Jack-in-the-bush, sauce-alone, hedge garlic and poor man’s mustard, this plant is a shade-tolerant biennial that can be found thriving in woodlands and along riverbanks. 

Why is it such a problem?

Considered the ‘purple loosestrife’ of woodlands, garlic mustard steals light, moisture and nutrients from other native plants. Its aggressive, rapid growth allows it to form a dense carpet of foliage, blocking light from other low-growing plants, including tree seedlings. 

According to the Committee of the Status of Endangered Wildlife in Canada, garlic mustard has threatened the survival of two species of woodland plants. The wood poppy is classified as endangered and the wood aster’s status is threatened. The plant has also been linked to the decline of the trout lily (dog tooth violet), trilliums and other native wildflowers in Canada.  It also threatens trees by harming beneficial fungi essential for healthy growth.

Biology

•  flowering plant that produces a low rosette of coarsely-toothed leaves in its first year

•  rosette leaves remain green over winter

•  early the next spring the plant develops a tall stem (up to one metre or 3 ft) with terminal clusters of 

   white flowers that mature into many long thin seed pods

•  plant dies after seeds mature

•  vigorous plants produce thousands of seeds

•  seeds remain viable in the soil for six years or more but most germinate in the second year

•  seeds are spread by people and animals

•  no known natural predators in North America

•  not eaten by deer which puts extra pressure on native plants

History in Canada

•  brought to North America in the 1800's by European settlers to use as a potherb and medicinal plant

•  most abundant in southern Ontario and southern Quebec with limited populations in British Columbia 

   and New Brunswick - not reported in British Columbia until 1948 and New Brunswick until 1968

•  first recorded in Toronto in 1879 - by 1900 had been found in Ottawa, Kingston, and Quebec City

Impact on Trees

•  grows mainly in deciduous forests - dense stands 

   suppress native tree seedlings, such as Sugar 

   Maple, Red Maple, and White Ash

• harms mycorrhizal fungi that trees rely on for nutrients

Control