The Lake County Forest Preserves are at war. It’s a conflict with frontlines across the county, likely invisible to most residents who don’t know about the infestation that plagues the landscape: buckthorn.
While visually unremarkable to the layman, the plant is the bane of people like Matt Ueltzen, the manager of restoration ecology with the forest preserves, who is one of dozens of staffers and teams of volunteers that work year-round to combat the invasive species that has detrimental impacts on local ecosystems.
Today, more than 50% of Lake County’s trees are buckthorn. At the Edward L. Ryerson Conservation Area, Ueltzen pointed out a few small buckthorn shrubs, maybe a few feet high. The tips of their trunks have a pair of buds resembling deer hooves.
While they may seem small and mundane, Ueltzen noted the area is heavily managed. Elsewhere, the plant can grow as high as 25 feet, most often along transportation corridors that lack plant management.
According to Andrea Kramer, senior director of restoration ecology at the Chicago Botanic Garden, Lake County, and the North Shore in general, are considered by some to be “ground zero” for the buckthorn’s introduction, where it was brought over from Europe in the 1800s for hedges.
But its competitive advantages have allowed it to outperform native plants. Ueltzen said it spreads seeds at a young age, leaves out earlier in the spring than native plants and remains green into the fall.
That means it can rob resources like sunlight and water from native plants, he said. While it’s been around for centuries, he said it’s exploded in the last 50 years, becoming “ubiquitous” and almost guaranteed in any areas that have been previously disturbed.
In Lake County, with its agricultural history, that’s just about everywhere.
“It’s spread like wildfire across most of the country,” Ueltzen said.
Fighting it is difficult. Buckthorn is something of the plant equivalent of the mythical hydra. Kramer said simply cutting the plant isn’t enough, since it can regrow with an even denser sprouting of limbs. It needs to be treated with herbicides or, if the native plant population in the area is healthy enough, destroyed as part of a prescribed burn.
According to Ueltzen, fall is a good time to identify buckthorn, since it remains green longer than native plants and visually stands out. The forest preserves offer various resources online about how to remove buckthorn, including herbicides. It’s part of a broader effort to drastically reduce the plant throughout the county.
Since the seeds are spread by birds who eat their berries, simply managing them within the preserves’ borders isn’t a solution, he said. The forest preserves think “about how we can work with our neighbors and outside of our boundaries,” Ueltzen said.
“If we only think about clearing our borders, we’ll never win this war because we’ll constantly have that seed ring coming in from birds from our neighboring properties and outside of the preserve,” he said.
And for him and others, it really is a war.
“Lots of people hate this,” Ueltzen said with a smile, gesturing at a buckthorn plant.
Upsetting an ecosystem
Buckthorn “doesn’t share well” with native plants and animals, Kramer said, stealing water and sun from other plants.
It kills diversity in the ground layer, including flowers and grasses that support wildlife. Kramer said it also hurts microfungi that have a symbiotic relationship with the area’s oak trees.
Buckthorn’s shade also kills the younger generation of oak trees. Ueltzen said Lake County’s oak woodlands face a generational challenge — the centuries-old trees are dying out, and there’s a lack of younger trees to take their place.
Ueltzen said when buckthorn plants die, they increase the nitrogen on the ground, leading to a jump in arthropod populations that eat away the leaf litter, literally eating themselves “out of house and home.” That means overwintering bugs lose their shelter, and buckthorn gets even more space to grow.
The plant also contains a chemical called emodin, which prevents bugs and animals from eating it. That chemical seeps into groundwater, which can kill native amphibians like frogs and salamanders. While Ueltzen doesn’t consider it a risk to people, very small amounts of emodin in the water can have serious effects on developing frogs and salamanders.
“It upsets the whole ecosystem,” he said.
But public awareness about the invasive plant has been growing, both Ueltzen and Kramer said, as has interest in stewardship. Dealing with such a challenge requires consistent work and resources, Kramer said, and even restored areas with healthy native plant populations require human intervention, such as prescribed burns.
“You can’t just do it and let the system take care of itself. Humans have always interacted with these systems,” Kramer said.
