With the snow receding, green vegetation is a welcome sight, but that green may warrant a closer look. For forest and woodlot owners, garlic mustard, Alliaria petiolate, is an early green in need of control before it takes control of the whole forest understory. With its historical roots in Europe, garlic mustard doesn't have any native natural controls here in the U.S. Given its real roots exuding the chemicals that alters the soil and discourages mycorrhizal fungi and native plants, this biennial can quickly become a monoculture. Since each plant is a prolific seed producer and seeds readily stick to shoes and wildlife, it doesn't take long for garlic mustard to spread. By July garlic mustard starts dropping its seeds and continues to do so through early fall.
If you discover garlic mustard, it's important to eradicate it before it spreads. It is easy to pull particularly in moist soil. Schools and young people have successfully pulled garlic mustard as it seems to be enjoyed as a competition of who can pull the most. If they don't get all the roots, the plants may grow back; however, research has suggested that they may not have time to seed out that season. Obviously, it's best to get the roots to avoid the risk of ambitious regrowth and seed production.
Larger patches of garlic mustard may be controlled with herbicide. However, herbicides can do collateral damage to nearby native plants. In garlic mustard monocultures, various herbicides can be effective although it is important to use a selective herbicide to avoid damage to native grasses. Some research has suggested that if large garlic mustard monocultures are left alone, they will in many years decline in numbers. In some areas that may make sense however in West Central Wisconsin where garlic mustard has not spread that widely, "letting the plant go" will allow the plant to spread to other areas. One issue is that there is virtually no way to prevent animals from tracking through a huge area and transporting seeds to other shady or disturbed sunlit areas. Similarly, there is not adequate research to suggest the consistency of response, the length of time necessary for population reduction, and the impact of long-term monocultures.
Several "natural enemies" of garlic mustard have been located in its native lands and researchers starting in 1998 have been studying which insect would specifically need garlic mustard to survive and reproduce. A root mining weevil, named Ceutorhynchus scrobicollis, was found to be specific to garlic mustard. It has gone through considerable testing nevertheless further agency reviews are in process before approval will be given for release of this bio-control option in the United States. This offers future hope for those large monocultures of this invasive plant. In the meantime, we should remove all garlic mustard plants or at least the second-year plants before they set seeds. If second year plants have already created a seed bed in the past, then removing or spraying plants is strongly encouraged for the few years (up to five) to deplete the seed bed. This can seem daunting, but the reward is a diverse native landscape. For help with plant identification and further information about invasive species contact Lower Chippewa Invasive Partnership at 715-539-2766 or email@example.com.