Prevent Garlic Mustard from Setting Seeds

Garlic mustard plants flower throughout the spring and summer and then spread seeds by the thousands. Anyone with undisturbed, natural areas around their home probably already knows how invasive this weed can be to more desirable plants. Garlic mustard has spread throughout most of northern Illinois in the last few years. It can be found in most places that are somewhat shady, whether in a home lawn area, woodland, fencerow, or wherever conditions are appropriate. It spreads rapidly and can displace native or other desired plants in a relatively short time. Each plant can produce thousands of seed which can be spread by wildlife, humans, water, or other means.

In Illinois, the plant has mainly a biennial life cycle, completing its life over a two-year period. After germinating in the spring, the plant usually stays in the rosette stage for the first year, appearing as a low plant of heart-shaped leaves, each about two to eight inches in length. The leaves also have irregular tooth margins on them. The next spring, the plant sends up a straight, rather slender flower stalk with small white, four-petaled flower clusters which will eventually develop seeds. The flower stalks usually are about one to two feet in height. Since the plant only flowers in the second year, the plants may appear less numerous in some years. That can be deceiving, since the plants are just waiting to complete their life cycle.

The goal is to prevent seed development and spread until the existing seed bank is exhausted. This may take several years in a confined area. Cutting and pulling plants before they set seed is one method that can be done in smaller areas, but can be too labor intensive for large patches. Controlled burns or herbicides may be needed in larger areas. Both should be used in a timely manner so to prevent seed development. Herbicide treatments work best in the spring and fall when the plants are actively growing.

For further information, contact the local University of Illinois Extension office. Also many offices of the Illinois Department of Natural Resources, Soil and Water Conservation Districts or other local park or forest preserve district will have related information.

June/July 2004: Prevent Garlic Mustard from Setting Seeds | Gypsy Moth: Know the Facts | Wetlands and Mosquitoes | Understanding Herbicides | Choosing Home Lawn Care Services