The Free Press, Mankato, MN

December 4, 2012

Mice, drought foil Million Tree effort

By Dan Linehan
Free Press Staff Writer

MANKATO — In 2008, Malda Farnham and a team of volunteers planted about 4,000 tree saplings along a Mankato hillside overlooking Highway 14.

“I wanted to see a forest there, but it just didn’t do it,” she said.

It’s difficult to count how many trees have survived three and a half difficult years, but it’s probably on the scale of 100 — there are surely more than 10 and far fewer than 1,000. And most of the trees that have survived have failed to thrive.

The 500 or so trees planted along County Road 90 south of Mankato fared little better. 

Perhaps a few dozen red cedars look relatively healthy, but most of the maples and basswoods are dead and the remainder are struggling.

“Pretty grim,” said Tom Hagen, of North Mankato.

The Million Tree Project, born from the planning process Envision 2020, had an ambitious goal that has been largely thwarted by mice and drought.

“I haven’t given up, but it’s very disheartening,” Hagen said.

The drought is well-documented; Mankato is 19 inches of rain below average since this August, said Mark Tarello, chief meteorologist at KEYC-TV. May was the most recent month with above-average rainfall.

In a walk around the County Road 90 site, Hagen demonstrates how most of the shoots are so dry they snap at a light pressure. These shoots are dead, but some are flexible and have some life in them.

“I think the real story here is the drought,” Hagen said.

The fact that only the red cedars have thrived makes sense to Scott Moeller, the director and interpretive naturalist for the Linnaeus Arboretum at Gustavus Adolphus College.

“Eastern red cedars are just really tough native trees,” he said. “Secondly, generally speaking, coniferous trees are better adapted for extreme conditions like this.”

Partially submerged mouse burrows criss-cross both sites.

Many of the trees on both sites have been girdled, their bark removed in a full circle around the tree, near the bottom, by mice. This either kills the trees or forces them to shoot up new stems, which they can only do so many times.

“The mice are the big culprits,” said Farnham, a Mankatoan.

Farnham has tried to keep the mice away by wrapping a sort of tape around the trunk of trees at a Highway 14 site, along Good Counsel Hill. It works, but it would be far too time-consuming for Farnham to wrap hundreds of trees. She has already spent many hours on this hill removing invasive species like buckthorn to give the trees a chance.

Hagen said mice do well in drought, which helps to explain their numbers.

The Million Tree Project was always an experiment to learn what sort of plantings worked best in each place, Hagen said. And some of the trees have survived. If they grab a foothold, nature may take over and expand the forest.

Hagen said it would be best to wait until the drought is over before trying again.

Farnham said the mice could perhaps be counter-acted with barriers, but that, again, would take a lot of work.