Garlic Mustard

Alliaria petiolata
Brassicaceae (mustards)

Garlic mustard produces a characteristic fragrance of garlic from all parts of the plant. Plants flower and fruit when 2-4 feet high. Blooms May through June. Plants usually produce 1 flowering stem but may have as many as 10 stems from a single root. Flowers are numerous, small, white, 1/4 inch across, and are borne in a terminal raceme at the apex of the stem and also at some leaf axils. Each flower has 4 white petals that narrow abruptly at the base. Basal rosettes have dark green, kidney-shaped leaves. Stem leaves are sharply toothed, triangular, alternate, and have petioles (leaf stems). The leaves also have large teeth around the margins and are 2-3 inches wide. Seeds are black and produced in narrow podlike capsules (siliques) 3/4 to 3 1/4 inch long.

Height: 2 to 4 feet.
Habitat and conservation: 
This species occurs most frequently in upland and floodplain forests, savannas, and along roadsides. It invades shaded areas, especially disturbed sites, and open woodland. It is capable of growing in dense shade and occasionally occurs in areas receiving full sun. It prefers soils with an abundance of calcium and does not do well in acidic substrates.
Distribution in Missouri: 
Scattered in at least 19 Missouri counties; most prevalent near the Missouri, Current, and Jacks Fork rivers.
Invasive. A native of Europe and Asia that was brought to the northeastern states by immigrants, who used it as a potherb, in salads, as a flavoring, and medicinally. It escaped their gardens in the early 1800s and has become a serious threat to native ecosystems throughout the eastern United States, but it has only been found in Missouri since the 1970s. Since its arrival in our state, it has spread rapidly.
Life cycle: 
Garlic mustard is a biennial herb. Seeds germinate in early spring, young plants overwinter as basal rosettes, and adults bloom from May to June the following year. Each plant dies after producing seed. Seeds disperse when the siliques (pods) split at maturity in August. Seeds have a 20-month dormancy period and do not germinate until the second spring after ripening. The species reproduces readily from its numerous seeds.
Human connections: 
This plant has a long history in Europe as a potherb and salad green. The seeds have been used for their oils. The plant has been used medicinally, too. Unfortunately, the insects and fungi that keep this plant in check in Europe don’t live in the Americas, setting the stage for trouble.
Ecosystem connections: 
Garlic mustard crowds out native plants and degrades wildlife habitat. High tannin levels in this plant make it unpalatable to deer, giving it a competitive edge in areas of deer browse. Garlic mustard also produces chemicals that inhibit other plants, allowing the invasive population to expand.
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