Invasive Plant Species – They Have to Go!

Photos courtesy of the author.

Menard County Trails and Greenways is a not-for-profit organization dedicated to improving conservation, conservation education, and recreation in Menard County. We’re based out of Petersburg, just 2 miles north of Lincoln’s New Salem State Historic Site, where its namesake lived and worked from 1831 to 1837. Several miles of trails wind throughout the nearly 700 acres of rolling hardwood forest above the Sangamon River, giving visitors a glimpse at what the landscape was like in Lincoln’s time. Or does it?

Chris Evans, the Illinois Extension Forester, explained that the forest at New Salem in the mid-1800s “ranged from bottomland species such as sycamore and cottonwoods close to the river, with sugar maple, shellbark hickory, bitternut hickory, black walnut, and northern red oak in the more well-drained portions of the bottomland and up the toe slopes. Ironwood, musclewood and spicebush would have comprised the understory. The side slopes and uplands were dominated by oaks and hickories and had an open nature due to somewhat regular fires that spread from adjacent prairies and savannas. The extra light created from the fires contributed to the establishment of a well-developed understory of grasses and forbs.”

Today, the forest’s understory at New Salem is dominated by invasive bush honeysuckle and garlic mustard. Both plants were intentionally introduced into the U.S.

Honeysuckle species were introduced from eastern Asia as landscape ornamentals as early as the mid-1700s. According to Ryan Pankau, Horticulture Educator for the University of Illinois Extension, “Sometime between the 1920s and the 1950s, bush honeysuckle became naturalized in Illinois, meaning that this non-native bush had spread to natural areas and its reproduction was sufficient to maintain or expand its population. Today, this exotic invasive species is present in every county in Illinois.”

Garlic mustard, a native of Europe, was brought to the U.S. by immigrants as an edible and medicinal herb. It was first recorded in New York in 1868 and in Illinois in 1918. It has since spread to a majority of counties across Illinois.

Both species pose similar threats to our hardwood forests. They leaf out early in spring before native species and spread so quickly and densely that they form monocultures that compete with native plants for light, water and nutrients. They are also allelopathic, meaning they contain chemicals that diminish the viability of other plants growing nearby.

Without the ability to reproduce, our forests are clearly threatened, as are the mammal, bird and insect species that depend on the native forest plants for food and shelter. The loss of native hardwood forest habitat threatens our quality of life by diminishing our ability to enjoy walking/hiking, hunting, looking for spring wildflowers, bird watching and collecting mushrooms. Landowners also risk losing the ability to harvest timber.

Concerned with the profound invasives problem at New Salem, Menard County Trails and Greenways decided that a volunteer project to remove invasives there aligned perfectly with our organizational goal to improve conservation, conservation education and recreation in Menard County.

In 2019 we reached out to the Illinois Department of Natural Resources (IDNR) with the idea for a volunteer project. After struggling for over a year to find the right fit, a call from Ray Geroff one October day in 2020 was a most welcome surprise. Geroff, our District Biologist with the IDNR Division of Natural Heritage, asked if we’d be interested in a project to restore the 65-acre area around the Cardinal Ridge Trail, with its older growth oaks and hickories, to its historic character. Under Geroff’s supervision we would be working as Volunteer Biologist Associates under the parameters of the Division of Natural Heritage Volunteer program, which included developing a 5-year Plan of Work (POW).

The following February, amid COVID-19, we held a project information and volunteer recruitment meeting via Zoom, and by April our 5-year POW was submitted and approved by IDNR. The POW includes five units—Units A through D comprise the portion of the site located on the east side of Route 97. Unit E is a small area behind the Lincoln Statue at the main entrance to New Salem.

We immediately planned the project kickoff event with a garlic mustard pull in late April, followed quickly by two more such events. All together we collected 30 bags of garlic mustard that first spring.

Over the summer two volunteers took the Illinois Department of Agriculture pesticide training and were licensed, and we were officially ready to get busy with honeysuckle removal. Before embarking on our primary area of focus, Unit A on Cardinal Ridge, we tackled Unit E. The father of Karen, one of our volunteers, had been a regular volunteer at the site years before. After he passed, family members started sending memorial donations with requests to have trees planted in his honor. Karen chose the Lincoln Statue area (Unit E) because that had been her dad’s favorite place. Karen did most of the work removing the honeysuckle and planting native trees July through September.

Honeysuckle removal within Unit A on Cardinal Ridge began with five volunteers joining our Natural Heritage supervisor, Ray Geroff, on November 5, 2021. Geroff worked with a 14-inch battery powered Stihl chainsaw. Another volunteer lugged about a heavy gas-powered chainsaw, while another used a gas-powered string trimmer with a blade attachment. The other three used loppers. After seeing how efficient Geroff’s chainsaw operated, within a week at least five volunteers had purchased their own lightweight and relatively quiet battery powered chainsaws. Since then, those saws and heavy-duty loppers have been the mainstay of our work, which consists of cutting each plant about 4 inches from the ground and immediately spraying the stump with glyphosate solution.

Larger tops are reduced in size with loppers and all brush is stacked in piles throughout the area. Because one of the desired outcomes of the future prescribed fires is for the brush piles to burn up, we are careful to make sure the piles aren’t too close to surrounding trees. We also orient the stems in the same direction, as it aids in the airflow needed to ignite the brush.

On February 27, 2022, four months after our first honeysuckle workday, we had cleared the interior section of the Cardinal Ridge Trail loop—just over 7 acres. On April 15, a few of us joined Geroff and his burn crew to conduct a prescribed fire in the areas we had cleared. A couple weeks later we held the first of eight garlic mustard pulls. Altogether, we removed 78 bags of garlic mustard from the site. The areas where the prescribed fire was most successful had the least amount of garlic mustard. We also observed that in the areas that didn’t burn, but were now receiving more light on the forest floor, we saw so many more spring ephemeral wildflowers than we’d ever noticed before.

Honeysuckle removal commenced again in mid-November 2022 and continued through February 2023. To date, volunteers have worked 792 hours clearing approximately 32 acres, or about half of our target area. On April 10, 2023 volunteers assisted Geroff and his burn crew with a prescribed fire. All but the greenest areas burned well, including the older brush piles. As this goes to press we’ll be scheduling garlic mustard pulls.

As we’ve improved the environment at New Salem, project interest within the community continues to grow. We’ve attracted many new members and volunteers and receive lots of favorable comments from passersby and social media about how much they enjoy hiking the Cardinal Ridge Trail where they now have open views of the forest.

A testament to the growing community awareness about the invasive species problem, were the 70 people who attended a Battling Invasive Plant Species: Why it’s important and what you can do! presentation by Chris Evans, the Illinois Extension Forester and Ray Geroff, the IDNR Natural Heritage Biologist.

“Our end goal for the open oak/hickory woodland is to restore it to a point where it would qualify to be listed on the Illinois Natural Area Inventory,” Geroff noted.

The Menard County Trails and Greenways volunteers are working to build community awareness and encourage action. If we want healthy forests to thrive and survive, we must all do our part to tackle the invasives problem on our own properties, on conservation lands and on public lands. Whether you live in town or have property in the country; whether you do the work yourself, help a neighbor, or hire a crew; honeysuckle, autumn olive, tree of heaven, multiflora rose, burning bush, garlic mustard and wintercreeper, to name some of the worst, must go!

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For 12 years (2002-2014) Terri Treacy was the caretaker of the Illinois Audubon Society’s War Bluff Valley Sanctuary and a member of the Board of Directors. In 2001, she began a 16-year tenure with the Illinois Chapter of the Sierra Club as an organizer, conservation field representative and legislative liaison. In retirement, she continues as a conservation advocate and currently serves as President of Menard County Trails and Greenways.