Garlic mustard, an invasive plant that deploys brute force and chemical warfare to take over the understory of hardwood forests, was the topic of the Chequamegon-Nicolet National Forest’s first virtual invasive species ID day Friday, June 5.

To date, only three pockets of the white-flowered plant have been found in Douglas County, according to Ramona Shackleford, coordinator of the Northwoods Cooperative Weed Management Area, which includes Douglas, Bayfield, Ashland and Iron counties. All three are in Superior and none are out of control. Shackleford said the largest is an acre.

“I went to Superior last week and met up with the Douglas County conservationist, Ashley VandeVoort, and Jane Anklam from the UW-Extension to hand pull the sites,” she said. “We did them in a day.”

Northern Minnesota is also battling garlic mustard.

"We have about 94 sites mapped just in the Duluth area," said Lori Seele, coordinator of the Duluth Collaborative Invasive Species Management Area (CISMA), which covers south St. Louis County.

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The top of a garlic mustard plant includes four-petaled white flowers with long, narrow seed pods below. (Photo courtesy of Lori Seele)
The top of a garlic mustard plant includes four-petaled white flowers with long, narrow seed pods below. (Photo courtesy of Lori Seele)

The invader has been found in private yards, parks, along Tischer Creek and has begun to pop up on trails. CISMA members pull it in public areas and leave brochures about the invader on doorknobs when it's spotted on private property. It's not one of the top three terrestrial invaders the collaborative is targeting, but it's in the top five.

Early detection and action is key to halting garlic mustard's advance, Seele said.

"This is the time when it's most important to act," she said.

Along the Montreal River in Hurley, the invader has infested a 40-acre site that straddles the border between Wisconsin and Michigan. For 10 years, Hurley volunteers and elementary students have been hand-pulling the invasive plants. Some years, they’ve collected as much as 800 pounds of garlic mustard.

Stopping the invasive species is important work.

"In the end, invasive species affect our health," Seele said. "Just like COVID, they affect our health and our economics."

The plant has a two-year life cycle. The first year, it comes up as a carpet of ground-hugging rosettes. The second year, the plants can grow up to 4 feet tall with four-petaled white flowers and narrow seed pods jutting from the stem. Each plant produces hundreds of seeds that are viable for up to seven years.

“It can spread very fast,” Shackleford said, pushing native foliage out and producing chemicals that inhibit the growth of other plants.

She encouraged people in the area to watch for garlic mustard. The plants stay green throughout the winter and start growing early in spring. It’s one of the first white-flowered plants to emerge in Wisconsin in the spring, said UW-Extension specialist Mark Renz, and has an S-shaped taproot. If crushed, the plant produces a distinctive garlicky smell.

The plants can be hand-pulled in the spring (early May to early June) before the seed pods open. Seele said it's not too late this year, due to the cool spring.

However, people shouldn't compost it. Instead, bag it tightly until it becomes slimy. At that point, it can be brought to WLSSD for disposal.

Shackleford also recommended that people wash off their shoes or tires after hitting a trail.

“You never know what invasive plants could get on your shoes or tires, so this is a good habitat to prevent the spread of invasive plants," she said.

Seele put it another way: Play, clean, go.

People can report garlic mustard sightings in Douglas County to the Northwoods Cooperative Weed Management Area, info@northwoodscwma.org or 715-373-6167; in the Duluth area, contact Seele at lori@stewardshipnetwork.org or (218) 393-9581.

UW-Extension offers a video on how to identify the plant. Videos on identification and hand-pulling can also be found on the Duluth CISMA website or Facebook page and the Northwoods Cooperative Weed Management Area website.