Garlic Mustard

Garlic Mustard

Garlic mustard [Alliaria petiolata (Bieb.) Cavara & Grande] is an aptly named biennial herb; all parts of the plant have a garlic odor. It grows in small-to-extensive colonies under forest canopies. In the first year, the plant appears as a basal rosette of leaves that remain green during winter. In the second year, stems emerge and grow, becoming 2 to 4 feet tall. Leaves are broadly arrow-point shaped with wavy margins. The flowers form in terminal clusters, and each flower has four white petals. The flowers give way to long, thin seed pods (siliques). In late summer or early fall the siliques mature, turn brown, and split open revealing small black seeds (Miller 2003). Garlic mustard grows in characteristic clumps, which are very visible in early spring due to this plant being much taller than most spring plants. First-year rosettes may be confused with violets. Garlic mustard can be distinguished by its strong garlic odor and the S-shaped crook just below the stem base.

High shade tolerance allows this plant to invade high-quality mature woodlands that are usually resistant to invasion by most species. In the southern Appalachians, bottomland forest with rich soils are at most risk of invasion. Garlic mustard disperses quickly due to the seeds being transported on animals fur (often deer), hikers clothing, and bicycle and car tires. Initial invasion usually occurs along forest edges or trails. However, it quickly spreads and can form dense stands throughout the forest which shades and out competes native understory flora. Since it begins growing very early in the season and is tall, it has the potential to restrict light from reaching spring ephemerals (Swearingen and others 2002).

Introduced originally as a medicinal herb from Europe in the 1800s, garlic mustard is displacing native forest understory plants and drastically altering habitat. This species produces prolific seed that can lie dormant in the soil for 2 to 6 years, building large seed banks. Germination occurs only in spring under favorable conditions. A biocontrol program has been started at Cornell University (Blossey and others 2001). Garlic mustard is invading from the Northeast and has yet to arrive in Florida, Alabama, Mississippi, Louisiana, or Texas.

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