Landowner Helpful Tip: Garlic Mustard Control

Garlic mustard (Alliaria petiolata) is a non-native, invasive plant that destroys healthy native forests and rapidly overtakes yard and garden areas. One of the worst invasive plants in Wisconsin, this nasty invader can completely monopolize the forest floor in just a few years. It thrives in a wide range of light conditions including full sun and shade, and will smother native spring plants through its high populations and early germinating abilities. Early spring is a good time to identify and control first-year plants and the mature second-year plants before they produce flowers and seed.  The plants look like ground ivy right after snow melt, but quickly grow to 3’ tall with a white blossom in the next month.  Crush a leaf and you will smell how it got the name Garlic Mustard.

To prevent spreading the plant:

1. Always brush off your shoes, clothes, bike tires, and camping equipment before leaving parks or other natural areas that are infested with garlic mustard to prevent its spread.

If you only have a handful of plants, take care of them before they become a big problem:

1. Hand-pull smaller patches of garlic mustard and bag it immediately for trash disposal. Label the bag "invasive plant for disposal" so no one is tempted to add them to a compost pile.
2. Garlic mustard can be mowed down to the ground before it flowers. However, re-visit the site to follow up on the re-sprouts by either hand pulling them or using a herbicide treatment.
3. Spot treatment with Roundup during the bolting/flowering stage of garlic mustard in the spring will also work effectively on the mature plants and can control the germinated seedlings. However, any drift of the herbicide can affect desired species, and so this treatment is recommended only at the worst sites that have less desirable species.

Garlic mustard plant in early spring 

If you have a larger patch, break the process down into smaller jobs so that you are not overwhelmed:

1. Spray with Roundup before desired plants emerge in spring, and in fall after other plants have gone dormant. Always read the pesticide label before applying the product.
2. Annually look for newly germinated plants every spring and fall. Plants green up first in the spring and stay green longer in the fall than most other vegetation.

Garlic Mustard in early June

This Landowner Helpful Tip is brought to you by the St. Croix – Red Cedar Cooperative Weed Management Area (SC-RC CWMA). This is a group of landowners like you. For more information about the CWMA and invasive species, visit our website: http://scrcinvasives.org/.