Garlic mustard belongs to the Mustard family (Brassicaceae). It is native to Europe, but has naturalized in many other parts of the world besides North America. The plant is a biennial (2-year life cycle), which self-pollinates and cross-pollinates (by insects). It can grow to about 1 to 1.5 metres in height. Found in forests, edge habitats, along trails, roadsides, and just about any disturbed area. Prefers shade but can grow in sun. Tolerates damp conditions but prefers drier sites.

The problems caused by this plant are similar to those caused by any invasive plant species, in that it displaces native plants and disrupts native ecosystems. Studies have also shown that it "Suppresses native plant growth by disrupting mutualistic associations between native canopy tree seedlings and below-ground arbuscular mycorrhizal fungi (AMF)." High concentrations of cyanide compounds in GM have been discovered in recent years, and these compounds may contribute to the reduction in mychorrhizal fungi abundance. Studies on the impacts of garlic mustard and methods of control are ongoing.

For more information we have some fact sheets here, in English and in French: http://www.ofnc.ca/fletcher/invasives/garlic-mustard/fact-sheet_e.pdf
http://www.ofnc.ca/fletcher/invasives/garlic-mustard/fact-sheet_f.pdf