It was a warm, sunny afternoon -- T-shirt and shorts weather. But the volunteers at a Maplewood nature preserve were girded for battle: long pants tucked into their socks, long sleeves with wrists wrapped with tape to protect the sliver of skin between glove and cuff.

Armed with shovels, they set off in pursuit of a noxious foe: wild parsnip, an invasive plant with sap so potent it can cause third-degree burns.

"I have a scar from last year," said leader Carole Gernes, pulling back her glove to reveal a fading reddish mark on her hand. "Watch out, Jan! There's one right by your head," she cautioned, as volunteer Jan Willkom backed dangerously close to a tall plant crowned with an innocent-looking froth of yellow flowers.

The hardy crew at the Applewood Neighborhood Preserve are members of the Invasive Plant Patrol, a pilot program of about 30 trained volunteers who prowl parks and open spaces in Maplewood and a wetland in Ramsey County. Gernes, a naturalist at Maplewood Nature Center and coordinator of the Ramsey County Cooperative Weed Management Area, recruits the volunteers, trains them in how to identify and eradicate new invasive species, sends them e-mail alerts and collects the data they report back to her.

They love plants enough to destroy them -- at least the aggressive ones that threaten to crowd out other species.

"It isn't just aesthetics," said Mary Beth Pottratz, a master naturalist from Minnetonka. "There's a critical need for biodiversity. If we lose the native plants, we lose the insects that used to be supported by native plants, and then we lose the birds and frogs that were supported by the insects."

Growing concern

Invasive plants have been around for a long, long time, but their spread is increasing, according to Gernes.

"People are active -- there's so much recreation." Four-wheelers and mowers on trail networks pick up pieces of plants and spread them far and wide.

Gardeners who are hungry for new landscape plants are another factor, she said. "There's a patch of tall ornamental grass near Hwy. 36 and [Interstate] 694 in Oakdale," she said. "It's covered the hillside and jumped the median. People think it's pretty, so they pull over, dig up a plug and put it in their yard. But it's a monoculture. Nothing else grows."

Many city and county governments try to police invasive plant species, often delegating it to parks, public works or natural resource specialists who have other responsibilities, she said. "But they cannot cover all the acreage. You need an army of people."

That's where the patrol comes in. It was adapted from an invasive-plant volunteer group in the eastern United States, Gernes said, a model that is "just starting to move to the Midwest."

Locally, the National Parks Service and some regional parks also have trained volunteers to help battle invasives. Ramsey County has discussed expanding the Invasive Plant Patrol throughout the county, but so far, "budgets are not allowing that," Gernes said.

So for now, she and her volunteers concentrate on Maplewood.

Protecting biodiversity

The patrol, now in its second year, is after emerging species.

"We target things you can find in small enough pockets that it's still possible to eradicate them," Gernes said.

Like buckthorn? Well, buckthorn is already too prevalent to prevent, she said. "Once it gets past a certain size, you can only manage, not eradicate."

Instead, they focus on plants like Japanese knotweed, a perennial that looks like asparagus when it first comes up in spring, then shoots to 5 to 10 feet tall. Eventually its root system becomes so massive and powerful that it can penetrate asphalt and break the foundations of buildings, Gernes said.

And cutleaf teasel. "There's a pocket of it in Roseville," she said. "It looks thistle-y but it gets much bigger, over 2 feet in diameter with an 8-foot-tall stalk. It's the most prickly thing I've ever handled in my life."

So far, the Twin Cities area has not been invaded by giant hogweed, a federally listed noxious plant. "To remove it, you need to wear a haz-mat suit," Gernes said. "If you cut it and it squirts in your eye, it's been known to cause permanent blindness. It's in Wisconsin. We don't want it here."

Big impact

At the Applewood preserve, Gernes guided volunteers to the parsnip patches, including one where the park adjoined a private back yard. "The guy fertilizes his lawn -- I've never seen 'em so tall," Gernes said. "He has scary parsnip!"

She showed the group how to identify the plant and distinguish it from heartleaf golden alexander (Zizia aptera), a benign native plant with a lookalike flower. Then she demonstrated how to dig a shovel blade under its roots and yank it from the ground. The pulled parsnips were piled and bagged to be taken to the city compost site, where the temperature gets high enough to kill the seeds, Gernes said.

Patrol volunteers fanned out, digging and pulling.

Karen Brooks, a master gardener from Maplewood, participated in the patrol last year, and can already see a big difference at the Applewood preserve. "Last year, it was almost 25 percent wild parsnip here. Now it's down to individual plants.

"What I like about this program is it's forward-thinking," she added. "We get things at the early stage, when it's still manageable and we can make a big impact. I do get a sense of accomplishment -- that I'm doing something very good for the environment and for wildlife. And from a selfish standpoint, I live in this neighborhood. I want them out so they don't spread to my garden."

Gernes said she's motivated by a desire to keep wild areas safe and beautiful for future generations. "I'm an outdoor person," she said. "I'd like my kids to be able to enjoy being outside without getting third-degree burns."

Kim Palmer • 612-673-4784