Brassicaceae: Alliaria petiolata

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Family Name

Brassicaceae

Common Name

Garlic mustard

Description

Alliaria petiolata is a biennial herb with a slender, white taproot with occasional fibrous side roots. In the first year, plants form a basal rosette of kidney- to heart-shaped leaves with scalloped edges, each 5–12 cm wide and attached by long petioles. In the second year, the plant produces an erect, simple or occasionally sparingly branched stem, generally 30–100 cm tall, with sparse, fine pubescence on young stems and leaves. Cauline leaves are alternate, triangular to heart-shaped, coarsely toothed, and decrease in size up the stem. The blades are shiny green, hairless or somewhat hairy. The leaves smell like garlic when crushed. The inflorescences are round clusters of a few to several white flowers. Flowering occurs from April to June, with small, white, four-petaled flowers arranged in terminal racemes. Each flower has 4 sepals (green, 2–3 mm), 4 white petals (5–6 mm, narrowly oblong), 6 stamens (4 long and 2 short), and a single compound pistil with a slender style and capitate stigma. Fruits are slender siliques, 3–6 cm long, linear, and green maturing to brown, containing numerous small, oblong, pale brown seeds (2–3 mm). Garlic mustard is a biennial species introduced to South Dakota and is considered invasive; it inhabits woodlands, forest edges, shaded roadsides, and disturbed soils, and has been reported primarily in the eastern and southeastern regions and along river corridors.

Additional Notes

Garlic mustard is not native to North America and is classified as a noxious weed in many states due to its aggressive spread and suppression of native understory vegetation. While edible and sometimes used as a wild herb or salad green (leaves and roots have a garlic-like odor), it is primarily noted for its negative ecological impact, reducing habitat quality for native insects and small animals by displacing their food plants.