It wasn't unusual for John Peterson to spend a weekend clearing 6,000 buckthorn trees from a patch of his 58 acres in Delano. But after seven years, his work still isn't finished.

"It was everywhere," he said. The infestation ranged from seedlings to trees a foot in diameter. "Once you start, it's like a never-ending project."

Years after the invasive buckthorn alarm was sounded in the Twin Cities area, suburbs — teeming with parks and random woodlands — fear they are losing the battle despite ferocious private and municipal efforts to eradicate it.

Cities are ramping up educational workshops and gathering armies of volunteers. But they barely make a dent.

"You can cut it, but if you're not aggressive then it can come back tenfold," said Chris Lord, district manager for the Anoka Conservation District. "Buckthorn is not something you have the luxury of just treating and walking away."

Buckthorn is an invasive plant from Europe that kills native vegetation by releasing toxins in the soil. It spreads rapidly in the shade and usually looks like a hedge but can mature into a large tree. Some female plants have poisonous berries that can cause cramping and diarrhea when eaten.

Nurseries actually sold people buckthorn until about 2000. The plant appealed to homeowners wanting shrubbery for privacy along their property line. Back then, few understood the implications.

Now, the Minnesota Department of Agriculture classifies buckthorn as a "restricted noxious weed"; it's illegal to import, sell or move it.

'A time bomb'

Burnsville is one suburb that has struggled to contain the spread of buckthorn, which can be identified by its egg-shaped leaves, fine-toothed margin and three to four indented veins branching out from the leaf tip.

Peggy Sears, of Burnsville, who has seen buckthorn's rapid growth in the land behind her townhouse, called the plant a "time bomb," adding: "It's not going away, but we don't know quite what to do."

Caleb Ashling, natural resources technician for Burnsville, said the leafy plant — which has no natural enemies — has invaded almost every shady area within the city that isn't currently treating it.

Several Department of Natural Resources grants allowed the city to begin ramping up efforts to remove the plant about five years ago; in 2009, Burnsville disposed of 41 semitruck loads of wood-chipped buckthorn.

But removal is "not something that happens overnight — or even in one year," he said.

Three years ago, Burnsville created a "Nominate Your Neighborhood" program because it didn't have the funds to support a citywide buckthorn pickup effort.

The program maximizes funds by encouraging homeowners who are active in their communities to work together in removing the pest, which the city would then dispose of.

As of this year, the city has picked up about 2,400 cubic yards of buckthorn from participating neighborhood groups, Ashling said.

Over that same time period, residents have used Burnsville compost site drop-off days to get rid of another 1,100 cubic yards.

Property values affected

Earlier this month, nearly 40 Burnsville residents attended an information meeting to address the problem. Cheryl Culbreth, owner of Landscape Restoration, told the group that everyone should care about the spread of buckthorn because it affects more than one's own back yard.

Buckthorn diminishes property value, she said, as well as the ecosystem.

"I don't think wildlife can adapt to these new plants at a rate rapidly enough to survive," Culbreth said. "Once we start losing species, you don't get them back.

"Some people say it's a losing battle, and I don't know, maybe it is. But there are many tools in the toolbox to help fight it."

Doris Herickhoff attended the meeting with her neighbor to get a better sense of what she's up against in her own back yard.

Herickhoff has been beating back buckthorn for nearly five years on the undeveloped land behind her townhouse in an attempt to build a flower garden. She even bought a small chain saw to keep on top of the problem, but she said her work is cut out for her.

At the meeting, Herickhoff changed her mind-set about how to approach the pest. "Don't go into this thinking you're going to eradicate it; come to learn."

Buckthorn blaster

Most forestry experts agree the cut-stump method is the most effective in combating buckthorn — whether one single bush or an entire forest.

The method involves chopping down the plant as close to its base as possible and then applying herbicide along the outer edges.

Several types of herbicides may work, but Culbreth sells a handheld glyphosate applicator with a foam tip for $6. She adds a dye to the chemical so homeowners can keep track of which plants have been treated.

While applying herbicide once may kill that particular buckthorn plant, years of follow-up are typically required to keep an infested area at bay — which is why it's so hard to control, she said.

Chris Lord, of the Anoka Conservation District, oversees a project at the Anoka Nature Preserve that has cleared buckthorn and other invasives from nearly half of its 200 acres. The effort is part of a pilot program launched in 2008 by the state of Minnesota with the goal of restoring natural habitat and gaining a fuel source in the process.

Until recently, buckthorn was removed almost entirely with hand equipment and burned onsite. This project recycled the mulched brush as fuel at the District Energy plant in St. Paul.

The Anoka project is one of 24 that received $886,000 in state grants over the last five years to remove invasive plant life from hundreds of acres of parks, preserves and other areas.

Sentencing to Service inmates and volunteers applied $30,000 worth of herbicide to buckthorn trunks when the project began last October, Lord said, and now native oaks are starting to return where they were once snuffed out.

But work is far from finished there. This October, another 66 acres will be burned to kill off sprouting buckthorn seedlings and even more herbicide treatment is required, he said.

Lord said he focuses most of his efforts toward scarcely populated regions of buckthorn, because that way you can actually be effective; there's little you can do about a wall-to-wall infestation, he said.

"If we can prevent the loss of high-quality habitats to buckthorn until a biological control is found … then it's worth it."

A success story

Peterson, of Delano, was in denial over a buckthorn problem on his idyllic property.

It wasn't until about 2008 when he and his wife attended a state-sponsored landowners' tour in Eden Prairie that showed some buckthorn infested woodland, that he began to understand. "The thought of [our land] looking like that was a real eye-opener," he said.

Peterson began treating his 58 acres with the cut-stump method and burning the brush in mountainous piles. He spent more than 500 hours a year removing the plant — often ripping out thousands of roots in one weekend — all while keeping meticulous records of where he'd labored.

With a background in statistics, Peterson used skills from work to manage the 100 wheat patches he owns. And seven years later, he notices a real difference. Native plants are coming back and passersby can finally see the forest floor.

He considers himself a success story, but maintaining all his hard work will require frequent checkups.

"It's not an impossible task, but it does take a tremendous amount of time," said Peterson, who's now retired. "If I was still working, we couldn't have done this."