Garlic mustard Invasive garlic mustard © TNC

Stories in Indiana

Journey with Nature: Garlic Mustard

Garlic mustard is considered one of the most destructive invasive plants in our state.

Oh, garlic mustard, why must you be so troublesome? This invasive plant can be found all across Indiana and is hard to get rid of, like most invasive species.

According to the Indiana Native Plant Society, garlic mustard is considered one of the ten most destructive invasive species in Indiana today. Fortunately for us, we have options to rid ourselves of this pest of a plant.

The Garlic Mustard's Life Cycle

Garlic mustard (Alliara petiolata) can be found throughout Indiana, invading our lawns, woodlands and other areas with the appropriate shady conditions. A native plant of Europe, garlic mustard is self-fertile and is very difficult to eradicate once it is established in an area. It spreads rapidly and unfortunately, displaces native or other desired plants in a relatively short period of time. Each plant can produce thousands of seeds which can be spread by wildlife, humans, water, or other means.

Garlic mustard has a biennial life cycle, meaning that it completes its life cycle over a two-year period. Seedlings germinate in the spring and form into basal rosettes -a low cluster of heart-shaped leaves – by midsummer. Immature plants will overwinter as rosettes that stay green and continue to photosynthesize during periods when temperatures are above freezing – giving them a head start over native and other desirable plants in the area. Regardless of when it germinates, the plant will remain in the rosette stage most of its first year.

All plants that survive the winter produce flowers in their second year and then die. An average plant produces 400-500 seeds that germinate readily in both well-lit and shaded environments. In the following spring, the garlic mustard will shoot straight up into a tall, slender flower with clusters of small white, four-petal flowers. Since the plant only flowers in the second year, the plants may appear less numerous in some years. This can be misleading, since the plants are just waiting to complete their life cycle.

How to Do Away with Garlic Mustard

Eradicating garlic mustard is easy work, but takes time. Lots of time. Vigilance is key, as garlic mustard can sprout up even when you're sure that you've gotten rid of every last one. The ultimate goal in removing garlic mustard is to prevent seed development and spreading until the existing seed bank is depleted. Unluckily for us, this may take 2- 5 years in any confined area. Cutting the flowering stems at ground level and pulling plants before they set seed is one method that can be done in smaller areas, but may be too labor intensive for large patches.

It's important to know when pulling garlic mustard you should always make sure that the taproot is completely removed or the plant will re-Garlic mustard its sprout. All cutting should be bagged, dried and then burned or buried deep into the ground. Contact your local landfill to see whether or not they will do this for you.

Controlled burns or herbicides may be needed in larger areas as way to lower labor costs. Both methods have potential drawbacks. Fire for instance can be ineffective if too cool or too hot. Fire that is too cool may not have an effect on the plant removal; instead it may just increase the presence of garlic mustard. Fire that is too hot can change the composition of the soil’s top layer. Herbicides have negative impacts on other plant and animal species and could possibly contaminate groundwater if directions are not followed carefully. Herbicide treatments are best left in the spring and fall when plants are actively growing. Always remember to wear protective gear and to read instructions carefully!

The method you choose depends on the size of garlic mustard infestation you have, and the type of environment the plant has invaded. Regardless of method, eradication should always take place before seed development.

Garlic Mustard Pulls

The Nature Conservancy will occasionally have garlic mustard pulls at the nature preserves that need it. Check our event listings for upcoming opportunities.

For More Information

More information and links at the USDA / National Invasive Species Information Center