Catherine W. Idzerda" />

It's time to tackle the herb nobody likes: Garlic mustard

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Catherine W. Idzerda
Monday, April 4, 2011
— Why do we write about garlic mustard every year?

Because it matters.

Garlic mustard is the bane of the greenbelt, the blight of every woodlot, the bęte noire of gardeners and the sworn enemy of hunters, ecologists and parks department officials.

Need another reason? Just let us get our thesaurus for the adjectives and consult our list of affected people, animals and outdoor areas.

Garlic mustard, or alliaria petiolata to give the plant its Latin name, is an invasive species that has been taking over forests and other natural areas throughout the upper Midwest. A biennial herb, meaning it has a two-year life cycle, garlic mustard flourishes in the shade and has been furiously out-competing native plants.

Here's the worst part: In its second year, the plant produces hundreds of seeds that can remain viable for five years.

Garlic mustard is so productive and successful it can replace almost all native species in a healthy forest within 10 years, according to the Department of Natural Resources. It also is considered a "major threat to the survival of Wisconsin's woodland herbaceous flora and the wild life that depend on it," according to the DNR.

"As is the case with many invasive species, garlic mustard starts growing earlier in the season than the native species, and it can take over and shade out native species," said Joleen Stinson, community coordinator for the Rock County Parks Department. "Diversity equals stability—stability of soil, stability of the plant community."

That translates into healthier woodlands, which, in turn, translates to a better environment for everyone from hikers and bird watchers to snowmobiliers and hunters.

In Rock County, officials have been battling the spread of the plant for years.

So, how bad is it?

"It depends on which park we're talking about," said Stinson. "It's a significant program. In Carver-Roehl, Gibbs Lake and Happy Hollow, we have more serious infestations."

Friends groups and volunteers are the first line of defense. Every spring they come out in force, spraying and handpicking plants.

Beckman Mill and Magnolia Bluff parks have benefited from thousands of hours of work from friends groups, and not just in the war against garlic mustard. At Magnolia Bluff, volunteers have spent hundreds of hours removing garlic mustard and other invasive species such as buckthorn, multiflora rose and spotted knapweed.

The Rock County Parks Department helps by coordinating the county conservation grants that come from the DNR. The grants, which come to nearly $2,000 each year, must be matched by the county.

Stinson works with the Rock County Sheriff's Office's Workenders program, which allows people to work off jail time on weekends by doing community service work.

Workenders, under supervision from the sheriff's department, pull garlic mustard in the parks.

Designation could help protect parks from invasive species

Carver-Roehl and Magnolia county parks are two of Rock County's secret beauty spots.

Both parks have active friends groups who treasure their parks, but they are far out-numbered by county residents who haven't visited either spot.

In November, both parks were named "state natural areas," a distinction that will help preserve their unique features.

State natural areas "protect outstanding examples of Wisconsin's native landscape, significant geological formations and archeological site," according to the Department of Natural Resources.

-- Carver-Roehl was chosen because of its "outstanding southern dry-mesic forest and moist cliffs." Moist cliffs are shaded cliffs that are most often on north- and east-facing slopes. The shade provides a cool microclimate for ferns and mosses.

Spring Brook Creek created the park's limestone cliffs. Those cliffs support a variety of unusual species including bulblet fern, purple cliff, brake and liverworts.

The forest contains a healthy mix of basswood, sugar maple and red oak.

The park also is home to the graves of two of the county's oldest settlers, members of the William C. Chase families.

-- Magnolia was chosen as a state natural area because of its unexpected topography. It's strikingly different from the flat or slightly rolling farmland of the surrounding countryside, and it appears as though the glacier decided to leave a rocky and lush jewel behind for us to discover, thousands of years later.

The combination of limestone and sandstone bluffs, old growth trees, native forest floor and savanna plant species and the park's small patch of kitten tails—a threatened plant—make it especially important to protect.

More than 90 percent of the plants and 75 percent of the animals on the state's endangered and threatened species are protected in state natural areas, according to the DNR.

The parks' designation as state natural areas means every effort must be made to protect them from invasive species such as garlic mustard and buckthorn, said Joleen Stinson, Rock County Parks community coordinator.

From a practical standpoint, the designation sometimes makes it easier to obtain grant money for garlic mustard eradication and other projects.

Understanding Garlic Mustard

Ecologist and former Rock County Parks Department employee Rob Ballar was considered the garlic mustard guru. He spearheaded eradication drives and created an extremely clear overview of the plant, its habits and how to get rid of it.

Ballar's experience led him to formulate four rules:

-- All treatments must be aimed at reducing seed output. This is the highest priority.

-- All treatments should promote native flora.

-- All treatments should consider small-scale control such as hand-pulling of satellite infestations and large-scale control such as herbicide, string trimming and controlled burns.

-- Herbicide is strongly discouraged during the growing season because it kills native plants and creates more habitat for garlic mustard.

Listed here are the basics from Ballar and UW Extension sources. For more detailed information, visit, use the "County Directory" and go to the parks department page.

-- After snow melts in spring, second-year garlic mustard plants often are the only green to be spotted in the woods. About April 1, first-year seedlings emerge, creating small green patches often found next to the larger, second-year plants.

Recommendation: Since most of Wisconsin's native plants haven't yet emerged, now is a good time to spray herbicide. Remember, focus your attention on second-year plants, as they produce the seeds.

-- Second-year plants begin to bloom May 1.

At this stage, first-year plants have formed groups of leaves in a "basal rosette" pattern. Basal means the leaves form at the base of the plant in a circle around it. Leaves extend out from the central stem.

While first-year plants are creating those rosettes, second-year plants send up a stalk. Stalks are usually 1 to 2 feet tall and form clusters of white flowers. Be forewarned, however: Stalk height is no indication of health or age. A short plant can produce as many seedpods as its larger siblings.

Recommendation: April 25 to May 15 is the optimal window for hand-pulling, according to Ballar.

-- The middle of May: Flowers lowest on the stalks form viable seeds. As summer continues, flowers continue to bloom and form seeds.

Seeds and seed pods can fall to the ground at any time. In the plant's natural life cycle, however, seeds stay in their pods until late June or July, when they are fully formed.

In August and September, seed pods dry out and either fall to the ground or are carried off by wind or animals.

Recommendation: After May 15, plants should be bagged and tied. In the city of Janesville, invasive species should be put in clear plastic bags, labeled and placed a short distance away from regular trash.

Ballar described garlic mustard as the "Frankenstein" of the plant world. Even after being pulled up, the plant has been known to live long enough to form viable seeds. Plants pulled after May 15 should be bagged immediately.

Do not, under any circumstances, put them in your home compost bin.

Last updated: 5:04 pm Thursday, December 13, 2012

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