January’s Weed of the Month is garlic mustard (Alliaria petiolata). Garlic mustard is an edible, biennial herb that emits a strong garlic odor. It was brought to the United States from Europe and has naturalized in many eastern and Midwestern states. In Minnesota, it is widespread in the southern part of the state and is spreading north.
Garlic mustard is highly invasive. It grows in woodlands, and along trails and waterways. It outcompetes native understory plants, becoming detrimental to biological diversity. Garlic mustard forms rosettes after seed germination in early spring. In its second year, it produces flowers in May and June and spreads by seed. The plant dies after it produces seed.
The plant has distinctive characteristics to distinguish it from other woodland plants. In the rosette stage, the leaves are heart-shaped with toothed margins. When it produces flowers, the leaves are triangular; the flowers are produced in clusters at the tops of the stems and are small, white, and have four petals. The plant produces slender seed capsules that can be spread by water and soil movement on boots and equipment.
Garlic mustard is a restricted noxious weed and cannot be transported, sold, or intentionally propagated in Minnesota. It is recommended that this species be prevented from spreading to new areas and that smaller populations be eradicated.
Managing garlic mustard takes persistence and a focus on preventing flowering, making timing a key component to management.