How to Control Garlic Mustard in a Woodlot

Invasive species are often the first plants to leaf through the forest floor in the spring, making this an ideal time to manage your woodlot. Removing invasive plants gives native plants more sun to grow and more room to thrive. Where native plants flourish, wildlife benefits and local ecosystems become healthier and more balanced.

Garlic mustard

Garlic mustard is an invasive species capable of establishing dense colonies in woodlands, crowding out native plant species and displacing wildlife that depends on them.

It was first introduced to the United States from Europe in 1868 and is now distributed throughout the Northeast and Midwest.

Garlic mustard will begin to invade a woodlot from the edges of the tree line, around trails and near streams. It is extremely shade-tolerant and outperforms native plants in spreading quickly via animals, footwear, and off-road vehicles. Once mature, an average plant can easily produce over 100 seeds.

There is also evidence to suggest that the roots of garlic mustard produce a chemical that hinders the growth of nearby plants, according to Ohio State University Extension.

Identification

First-grade garlic mustard grows in a basal rosette. The plant consists of three to eight rounded leaves with wavy toothed margins forming a circle at the base of the stem. The leaves are wrinkled in appearance and stay green all winter.

The plant will then produce two to four large flower stalks in its second year. Plants that have reached maturity are more difficult to eradicate because they produce seeds, but have more identifying characteristics.

Sheets. Garlic mustard greens are heart-shaped to triangular with wavy toothed margins. They are 1 to 3 inches long and 1 to 4 inches wide, arranged alternately on the stem. They give off a garlic smell when crushed.

Flowers. Flowers begin to appear in small clusters at the end of each stem in mid to late spring. They are white with four petals.

Seeds. Pods are produced in early to mid-summer. They are 1 to 2.5 inches long and four-sided. The seeds inside are black, small and grow in a row.

Roots. Garlic mustard has a thin, white taproot.

Controlling Garlic Mustard

Weeding. It sounds odd to weed the woods, but it’s an effective practice for eradicating noxious weeds in the spring before they start to bloom. Garlic mustard can be pulled or dug, but it’s important to remove as much of the root as possible. This plant can sprout from fragments left behind. Plants should be bagged and burned after being uprooted.

This process will need to be done every year for several years because garlic mustard seed can remain viable in the soil for five years or more.

Pulling out plants that have started to flower is not recommended as this can perpetuate the spread of garlic mustard to other areas.

However, once the stalks have sprouted before the flowers open, the garlic mustard stalks can be cut a few inches above the soil surface and removed. If this tactic is used, the plants will need to be checked several times as new stems may grow from the remaining plant.

If seed heads have formed, you can cut them out in a paper bag to collect and burn them.

Weeding torch. A weed torch can also be used to kill newly sprouted seedlings. The advantage of using a weed torch is that it can kill tender seedlings without permanently damaging surrounding plants. However, a weed torch should only be used when conditions are wet and not windy so that flames do not blow away from the intended area.

Herbicides. The herbicide can be applied to foliage early in the growing season before pods form in areas of high plant density. However, be careful not to apply herbicide to desirable plants. It is crucial to spray all plants in the target area, otherwise those that survive will swell in the absence of competition.

First-year rosettes can also be treated in late fall when conditions are dry and temperatures are above 50 F after other plants have gone dormant, reducing the chance of damage from other plant species.

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