The invaders put up a formidable defense but buckthorn fighters in Mettawa are employing unique tactics to control the pesky shrubs.
Joined by DePaul University, volunteers not only are nurturing native plants on the former horse pasture at Riverwoods Road and Route 60, but have established the site as an incubator for groundbreaking research.
They hope to pinpoint quicker and less expensive techniques that can be used throughout the region to remove the nasty plant and restore areas to their native state.
"The (buckthorn) density was about one tree per square foot and they were about nine feet tall when we took them down," said Cheryl Pytlarz, president of the Mettawa Open Lands Association.
"Here is a village parcel, seven acres or so, that had maybe the worse stand of buckthorn any of us in the business had ever seen," agreed Keith Gray, secretary of the group and head of Integrated Lakes Management, a firm that specializes in restoration projects. "It was a challenge."
Buckthorn is an invasive species that spreads rapidly choking out native plants in its path. It blooms early, grows virtually anywhere, takes out topsoil and fosters erosion. Its berries are favorites of birds who "deposit" the seeds far and wide.
Professionals and volunteers are making progress in a five-year effort at Whippoorwill Farm, considered a gateway preserve by the open space group.
They'll be back to begin a third growing season from 9 a.m. to noon today to spread seeds, burn brush and eat hot dogs and s'mores. Volunteers, including kids, are welcome. Gloves and long pants are encouraged.
Removing the dreaded invasive species is one struggle. Getting native plants to return in their place is another.
In this case, the former horse pasture has presented researchers with a laboratory to see what method will work best.
"What we want to have at the end of this is having best management practices for anyone who wants to do restoration," explained Lauren Umek, urban ecology coordinator for the Institute for Nature and Culture at DePaul University. "It's (for) everybody from for-profit contractors to people in their backyards."
DePaul is employing variations of 10 methods on about two acres under its care. One finding is soil where buckthorn has been prevalent is loaded with nitrogen.
"That seems like a good thing but when it comes to natural ecosystems, that fertilizer favors weedy plants," Umek said. Planting corn is one strategy to remove the nitrogen.
"We're restoring the ecosystem, not just gardening," she said.
On the remaining land, Integrated Lake Management did the traditional method of cutting the buckthorn, applying herbicide and repeating as needed.
Another contractor, Tallgrass Restoration, shredded the buckthorn and tilled it into the soil. Techniques are being monitored and evaluated, and the program has created a buzz in the restoration community.
Eventually, the site will become an oak and hickory savanna with native flowers and grasses, available for passive recreational use. Notable results are a few years off as native plants first develop 12-foot root systems before flourishing on the surface.