6021 Development Drive, Suite 2, Charleston, IL 61920 info@colescountyswcd.org 217-345-3901 ext. 3

Protect Illinois forests by removing invasive garlic mustard this spring

Every spring, early blooming ephemeral flowers are a welcome sign from nature that winter is almost over. But Virginia bluebells, mayapples, spring beauties, and other native plants are fighting against invasive species for a place in Illinois forests. Forest owners, land managers, and natural area visitors can help. Now is the time to scout for and remove garlic mustard.

“Garlic mustard is a high-priority invasive species for Illinois,” says Christopher Evans, Research and Forest Specialist with University of Illinois Extension. “Large infestations limit the growth and productivity of native plants and threaten the long-term health of forests.”

Garlic mustard’s early spring growth can quickly cover the forest understory. Infestations form a monoculture that competes with native plants for light, water, and nutrients. This threatens wildflowers, tree seedlings, insects, wildlife, and future forests. Large populations reduce nutrients in the soil and release allelopathic compounds that slow the growth of other plants.

Infestations impact the ecosystem and reduce the ability to harvest timber, hunt, collect mushrooms, enjoy spring wildflowers, watch birds, and spend quality time in beautiful, healthy forests. 

“The best way to manage garlic mustard is to keep it out of your forest,” Evans says. “Large infestations take a lot of time and effort to control but catching plants before they spread is the easiest way to keep your forest healthy.”

Prevention methods include cleaning boots, tires, and horse hooves to remove seeds after visiting an area. Monitor for garlic mustard along pathways of entry such as forest edges, creeks, trails, and in disturbed areas. Mark plant locations with a map app or flags. Mark the location with a flag or mapping app to relocate it later. Landowners can discuss their concerns about invasives with neighbors and plan to work together to manage them.

Garlic mustard has a two-year, or biennial, growth cycle. First- and second-year plants will grow together and in large infestations will rotate dominance in the landscape every other year. Garlic mustard is easiest to identify in spring when second-year plants are flowering. The flowering stalk is 1-to-4 feet tall with triangular, toothed-edged leaves and its small flowers have four white petals. Those visiting recreational nature areas should report sightings to staff and with the EDDMaps app or online at www.eddmaps.org.

For those who have garlic mustard, Evans says there is a 6- to 8-week window in spring to remove plants before they produce seeds and spread further. Removing garlic mustard is a multi-year process that focuses on preventing at least 90% of plants from producing seeds to prevent spread. Be prepared to manage annually for at least five years to deplete the seed bank and plan for long-term monitoring to prevent reinvasions. Sporadic management can make infestations worse.

Removing garlic mustard is a multi-year process and control options include mowing, cutting, hand pulling, prescribed burns, and herbicides. No management method is entirely effective. Before treatment, develop a long-term strategy that considers available time and labor resources, as well as the infestation size and location. Get help with garlic mustard identification, explore removal options, and consult with an Extension educator at https://extension.illinois.edu/invasives/invasive-garlic-mustard

Adapted from an article by Emily Steele, University of Illinois Extension and information from the Illinois Extension website.