garlic mustard Alliariapetiolata (Bieb.) Cavara & Grande
Appearance
Alliaria petiolata is an herbaceous, biennial forb. First year plants are basal rosettes which bolt and flower in the second year. Plants can be easily recognized by a garlic odor that is present when any part of the plant is crushed.
Foliage
Foliage on first year rosettes is green, heart shaped, 1-6 in. (2.5-15.2 cm) long leaves. Foliage becomes more triangular and strongly toothed as the plant matures.
Flowers
Second year plants produce a 1-4 ft. (0.3-1.2 m) tall flowering stalk. Each flower has four small, white petals in the early spring.
Fruit
Mature seeds are shiny black and produced in erect, slender green pods which turn pale brown when mature.
Ecological Threat
Alliaria petiolata is an aggressive invader of wooded areas throughout the eastern and middle United States. A high shade tolerance allows this plant to invade high quality, mature woodlands, where it can form dense stands. These stands not only shade out native understory flora but also produce allelopathic compounds that inhibit seed germination of other species. Alliaria petiolata is native to Europe and was first introduced during the 1800s for medicinal and culinary purposes.