Garlic mustard may be Michigan’s worst woodland weed

This invasive weed is rapidly taking over the forest floor, replacing important habitat for plants and animals alike.

Garlic mustard is rapidly becoming one of Michigan’s worst woodland weeds. Its thrifty, biennial habit allows the plant to optimize growth before native vegetation greens up while sewing thousands of seeds with each mother plant. A native to Europe, it was originally introduced in North America by settlers for its “proclaimed” medicinal properties and use in cooking. (Just break a root or leaf and take a whiff.) Unfortunately, because of its invasive habit, garlic mustard is rapidly dominating the forest floor, changing woodland habitat for plants and animals alike. Given the chance, it will also invade the home landscape and even take over patches of existing groundcover.

Garlic mustard can be very aggressive and easily invade landscape beds.
Garlic mustard can be very aggressive and easily invade
landscape beds.

Garlic mustard (close-up) just before bloom.
Garlic mustard (close-up) just before bloom.

Understanding the life cycle

Garlic mustard is a biennial, meaning it completes its lifecycle in just two years. The first year it is a diminutive, even attractive little plant with clusters of 3 to 4 rounded- to kidney-shaped leaves with scalloped edges. At first glance, it may be mistaken for a wild violet. These first-year plants remain green throughout the summer season and into the winter, making it easy to check for invasion throughout the year.

Early the next spring, robustly growing garlic mustard plants send up a 20 to 40-inch bloom stalk bearing tiny white flower clusters. Leaves at this point, tend to lose their scalloped edges giving way to a more “toothed” appearance. Flowers pollinate quickly and become viable seeds within a few days after flowering begins. Seeds mature and disperse as the slender seed capsules dry out and flip around in the wind. By the end of August, the plant actually disappears. At this time, unsuspecting gardeners and woodlot owners forget about garlic mustard, thinking it has gone away until the thousands of seeds germinate and begin their aggressive march through the forest. Seeing a forest woodlot that has been completely taken over by garlic mustard is a strikingly disturbing scene.

Control measures

Any control method selected must be repeated for several years until residual seed from previous year’s plants has germinated. To a gardener, this could be a long time. Smaller garlic mustard infestations can be controlled with a watchful eye and rigorous hand pulling during spring before other vegetation greens up. (Now, late March, is a great time!)

The plants are relatively easy to pull but brittle, so be sure you are lifting the entire plant out of the ground and not just breaking off the top. If the plants have begun to flower and set seed, be careful to take the entire plant and not drop off any of those seed capsules.

Plants should be and bagged or burned (with permission) since research has shown that composting is not a consistently good option. A large percentage of seeds can withstand the compost heating process and may not be destroyed.

For larger stands, mowing or cutting has not proven to be the best solution either. If you can cut the plants before the flower buds have opened this is the best option to avoid future seed production. Herbicides can be used in the early spring or again in late fall when native vegetation will not absorb the product. The very nature of the forest floor is a very delicate so please read the label carefully before applying.

The bottom line is that people who appreciate the native beauty of their woodlands and would not like to see this aggressive weed move into their landscape beds should keep a vigilant eye and remove it as soon as it appears. You can also get involved in a local “garlic mustard pull” to help park lands and other valuable areas tackle the problem.

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