Prevent Garlic Mustard from Setting Seed

Garlic mustard plants are now or soon will be in flower. They then will spread seeds by the thousands later this season. 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.

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 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, though, since the plants are just waiting to complete their life cycle.

Each plant can produce thousands of seeds which are spread by wildlife, humans, water, or other means. 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. For a herbicide treatment, glyphosate, sold as Roundup and other trade names, works best in the spring and fall when the plants are actively growing. Since glyphosate will kill most green living tissue, be sure to read and follow all label directions and precautions before using it or any other chemical.

Offices of the Illinois Department of Natural Resources, Soil and Water Conservation Districts or other local park or forest preserve district may have related information.

April-May 2003: Planting Trees | Prevent Garlic Mustard from Setting Seed | The Roses Are Coming | Unusual Vegetables