Smoke will rise this spring from the oak forests of Battle Creek Regional Park, as Ramsey County continues its quixotic battle against the invasive buckthorn that has taken over much of the forest floor.

The county has received two grants totaling more than $200,000 from the Minnesota Department of Natural Resources to conduct a series of controlled burns at the park, along with mowing down, piling up and setting fire to the buckthorn that has decimated native shrubs across 100 acres of forest.

Once the buckthorn is removed, the hope is that sunlight will reach the seeds of native plants, which can lie dormant for years but still sprout when conditions are right, said Mike Goodnature, Ramsey County natural resource director.

"We usually give it a season to determine what kind of native growth made it," Goodnature said. "If it's good growth, we can save some of our funding."

If the native plants aren't growing back on their own, then the county will need to buy seeds and broadcast them in the woods, which can quickly get expensive.

A major challenge to restoration efforts is that buckthorn seeds also can lie dormant, waiting as long as five years to catch the right amount of sunlight and aggressively take back the understory of the forest.

Buckthorn is so prevalent throughout the region that even when Battle Creek is restored, the weeds could creep back in from every direction. Once re-established, buckthorn roots and berries are mildly toxic, causing the soil below to become bare and vulnerable to erosion, Goodnature said.

"Maintenance is a constant battle," he said. "Once you initially restore an area, you know that over the next 10 years the maintenance is going to be pretty heavy."

But Battle Creek has some advantages in fighting buckthorn. Its hills are steep enough that the sun-loving invasive struggles to spread on the shadier north sides of the slopes, Goodnature said.

"The goal is to get some very fast-growing natives in there that could then out-compete the buckthorn," he said.

If native shrubs thrive at the park, the county will only need to go back in to remove buckthorn every other year or so.

The county will send out notices to nearby homeowners once it has selected dates in the spring for the controlled burns, which officials intend to mimic natural wildfires that occurred before settlement, Goodnature said.