Garlic Mustard — A Nasty Little Invader

Garlic Mustard forms a monoculture in an Eastern woodland.

Early spring is prime-time to eradicate one of our most relentless local invasive plants: garlic mustard. Here’s what you need to know to ensure this nasty little invader doesn’t overtake your property or surrounding public lands.

Background

Garlic mustard (Alliaria petiolata) is a European herb that’s considered among the most destructive invasive species in the eastern United States. It spreads rapidly and is very difficult to eradicate once it becomes established. It can readily displace native plants in a very short period of time. Each plant can produce thousands of seeds which can be spread by wildlife, humans, water, or other means. If that’s not bad enough, garlic mustard is allelopathic, meaning it releases chemicals that hinder the growth of other plant species.

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In its first year, garlic mustard forms low-growing rosettes of kidney-shaped leaves.

Identification

Garlic mustard has a biennial life cycle, that is, it takes two years to fully mature and produce seeds. The first year it forms low-growing rosettes with rounded, kidney-shaped leaves, scalloped on the edges.  The second year (see picture lower right), it sends-up flowering stalks that range from 6 inches to about 3 feet. The upper leaves on mature plants are somewhat triangular in shape. The four-petaled flowers are small and white and form in clusters at the top of the stems. After a short flowering period they give-way to seed pods. A vigorous plant may produce as many as 8000 seeds, so it’s imperative that plants are eradicated before their seeds are disbursed.

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Second year plants produce stalks topped with four-petaled white flowers.

 

Eradication

The best method for controlling garlic mustard, or any other invasive plant, is to prevent its establishment. Learn to recognize garlic mustard and monitor your property regularly. If you find any plants, remove them immediately before they can spread.

Small pockets of infestation can easily be controlled by hand-pulling. This is best accomplished in the early spring when the ground is soft. Pull slowly and be sure to remove the entire root to prevent a new stalk from forming. Hand-pulling should be performed before seeds are formed and needs to be continued for up to five years in order to deplete any established seed bank. Garlic mustard plants can produce and distribute seeds even after they’ve been pulled, so it’s important to place plants in a trash bag and discard with your regular garbage. Or try one of these recipes to put this plant pest to good use.

For larger invasions, you might have to rely on applications of chemical herbicide. In dense stands where other plant species are not present, a glyphosate-based herbicide such as Roundup® can be an effective method for removal. It’s important to understand that Glyphosate herbicides are non-selective, meaning they will kill all vegetation they come in contact. Chemical applications are most effective during the spring (March-April) when garlic mustard is one of the few plants actively growing. Fall applications may be used; however other plant species still in their growing season may be harmed. In all cases, be sure to read the herbicide label carefully and apply only in the directed manner.

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