Garlic mustard is likely to be one of the worst invasive species in the Door peninsula area. It invades forests and forms dense populations that displace most native species. It is the only serious threat (to date) for the popular ephemeral species which are characteristic of spring in our sugar maple forests. It appears to do best in areas where the soil is underlain by limestone bedrock and will grow in both shaded and sunny sites, although it does best in forests.

Garlic Mustard has been very destructive in northern Illinois and southern Wisconsinand is rapidly spreading into northeastern Wisconsin. It is already present in Brown, Manitowoc, Kewaunee and Door counties, and is established in at least one major site as far north as Florence County.

Garlic mustard is a biennial species which does not flower in its first year, but produces basal leaves which overwinter. In the second year it flowers ,as shown in the photo, and after producing numerous small seeds, it dies. The seeds will quickly produce numerous new plants and after the first year both the basal leaves and flowering plants will be present.

If you suspect a plant is Garlic Mustard, you can crush a leaf and smell it. It is the only leaf of the type shown that will smell like onion or garlic. The numerous small flowers have 4 white petals, as do many other members of this family, which is the mustard family (it is not really a garlic, inspite of the name). Garlic mustard flowers very early in the spring and leaves should be visible year round, if not coverd by snow or leaves.