Control Those Weeds: Garlic Mustard

The majority of the information comes from various extension services and contacts that I have made in the 15 years that I have been a Master Gardener. This is not to mean that some of these weeds are not found in other regions of the U.S. I hope this information helps you to eliminate every gardener’s enemy, the lowly weed.

What it does:
Garlic mustard poses a severe threat to native plants and animals in the forests of much of the U.S.  Many native wildflowers that complete their life cycles in the springtime (e.g., spring beauty, wild ginger, bloodroot, Dutchman's breeches, hepatica, toothworts, and trilliums) occur in the same habitat as garlic mustard. Once introduced to an area, garlic mustard out-competes native plants by aggressively monopolizing light, moisture, nutrients, soil and space. Wildlife species that depend on these early plants for their foliage, pollen, nectar, fruits, seeds and roots, are deprived of these food sources when garlic mustard replaces them. Humans are also deprived of the vibrant display of beautiful spring wildflowers.

Where is it?
Garlic mustard is found in about 80% of U.S. states and several Canadian provinces.

Where did it come from?
Garlic mustard was first recorded in the United States about 1868, from Europe. It was likely introduced by settlers for food or medicinal purposes.

What Does it Look Like?

Leaves are roughly triangular and sharply toothed, a little over one to three inches wide and long becoming gradually smaller towards the top of the stem.
Flowers are continuously produced at the top of the long stalk. The flowers are white with four petals that form a cross. The flower is similar to others in the mustard family.

How Does it Spread?
Garlic mustard reproduces only by seed. Most seeds germinate within the first or second year after being produced but can remain viable in the soil for up to five years. Seeds require prolonged exposure to cold before they can germinate. Seeds germinate in the spring and form low growing flowers of dark purple to green, and kidney-shaped leaves. Leaves grow on stalks that are a half to 2 inches long called petioles. Young leaves smell of garlic or onion when crushed, although the odor becomes less intense as plants grow older. Seedling density in infested areas can reach nearly 17,000 per square yard

It spreads rapidly

Can It Be Stopped?
Because of the large area it can infect, control can be difficult. Here in Michigan the Department of Natural Resources each year asks volunteers to help pull plants before they produce seed in heavily infested areas. Besides pulling or cutting,  burning is effective if there is enough fuel to carry the flames. This is a limited measure however in dry areas where the fire spreading to other areas is a threat. We sure don’t want a repeat of the large fires in the western U.S.
Applying glyphosate (Roundup) in early spring or late fall when native plants are dormant can help. This is a non-selective herbicide which kills any plant that it touches; that is why it needs to be applied before native plants leaf out.
Please be especially on watch for this plant, if you see it, report it to your county extension, state department of agriculture, or department of natural resources. Once it gets a foothold it is EXTREMELY hard to kill.