Garlic Mustard (Alliaria petiolata)
WEED ALERT

Garlic mustard, a biennial herb in the Mustard Family, is native to Europe and Asia. It is believed that settlers brought this plant to North America for use in cooking and medicine. Six infestations are known in BC; four in the North Okanagan at old homesteads, and two in the Lower Mainland. In Ontario, garlic mustard infestations can be quite dense and advance quickly. Sites within BC have not yet become as aggressive. Garlic mustard is shade tolerant and predominantly found in rich, moist forests and wooded streambanks.

Garlic mustard Photo Credit: Dr. John Meade, Rutgers Cooperative Extension	Garlic mustard seedling

Biology

Garlic mustard is a biennial with dark green, kidney-shaped leaves which remains a rosette the first year. Second year plants grow a stem 0.3 to 1.2 metres high with triangular, alternate, sharply toothed leaves. Small, white, four-petal flowers develop in May in clusters at the end of the stem and occasionally in leaf axils. Seeds are black and form a single row inside slender, erect, pale brown pods (siliques) 2.5 to 6.5 cm long.

Reproduction

Reproduction is by seed, which are produced only by second year plants. Each plant produces hundreds of seeds, which may be scattered long distances by wildlife and human activity. Garlic mustard flowers are either cross-pollinated by insects or can self-fertilize, depending on conditions. Self-fertilized seeds produce identical plants that may enhance its ability to colonize an area.

Habitat 

Garlic mustard is most commonly found in shaded areas, even dense shade, but occasionally grows in locations receiving full sun. It occurs in river floodplains, forests, trail and forest edges, and along roadsides. Garlic mustard prefers moist areas but does not tolerate acidic soils. Disturbed sites are most susceptible to invasion and dominance.

Concern 

Garlic mustard, an early spring competitor, invades forest communities where it monopolizes light, moisture and soil nutrients, resulting in aggressive domination of the ground layer. It is a severe threat to many natural areas where it occurs because of its ability exclude many native herbaceous species.

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