Whip smart: Cottonwood planting takes root as worries grow

Volunteer Jeanne LaBore moves a tape measure
Volunteer Jeanne LaBore plots where young cottonwoods will be planted in St. Paul's Lilydale Park.
Elizabeth Dunbar/MPR News

When people hear about Maria DeLaundreau's summer cottonwood planting project, they think she's crazy. Plant more of those messy trees? What about the seeds?

"They're clogging up their air conditioners all the time, someone swallowed one on the way to work. The seeds are definitely abundant," she agreed.

They're also vital to the health of the floodplain forests. Cottonwoods provide habitat for eagles and shade for other tree species, and many of the young trees are not surviving. A National Park Service survey a few years ago found no cottonwoods smaller than 6 inches in diameter along the 72-mile Mississippi National River and Recreation Area through the Twin Cities.

It's not clear why the young trees are struggling, but until the answer's known, DeLaundreau decided to plant. On Thursday, she led a group of volunteers from the Mississippi River Fund, where she's working for the summer, and a youth Conservation Corps team in an experiment to find out how to help young cottonwoods sprout.

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Volunteer Ann Drivas of St. Paul
Volunteer Ann Drivas of St. Paul counts cottonwood seeds.
Elizabeth Dunbar/MPR News

In a clearing in woodsy Lilydale Park where Mississippi River floodwaters have recently receded, the group carefully plotted out where to do their planting. They then counted cottonwood seeds, pounded dormant cottonwood branches — called whips — into the ground, and placed delicate cottonwood seedlings into holes in the sandy soil.

Some of the young cottonwoods will be fenced in or protected by tubes to keep deer away.

"It'll be interesting to come back in two years and five years and see, did the seedlings take off? Did the seeds take off? Do we need to do anything else to support their growth?" said volunteer Jeanne LaBore of St. Paul.

LaBore, who in March also helped the Mississippi River Fund cut the cottonwood whips that were planted Thursday, said it's exciting work. "It's the mystery of it. Why are they not regenerating? There could be so many factors," she said.

Deer are probably not the main culprit. The river's lock-and-dam system and changes in precipitation patterns brought on by climate change are the primary suspects, said DeLaundreau, whose work is supported through the federally funded Minnesota GreenCorps program.

Conservation Corps volunteers plant cottonwoods
Conservation Corps volunteers plant cottonwoods at Lilydale Park.
Elizabeth Dunbar/MPR News

Park Service researchers noted that many of the large cottonwood trees — home to 84 percent of the recreation area's bald eagle nests — predate the lock-and-dam system.

Cottonwoods like spring floods that wipe out some vegetation and leave behind sand and sediment where seeds can easily germinate, DeLaundreau said. The lock-and-dam system has kept the river artificially high to allow for navigation. And flooding during the summer or even fall, which used to be unheard of, is happening more frequently, and it's not helping young cottonwoods get established, she said.

The other problem with the unpredictable flooding is timing, said Claudia Nanninga, a visiting research associate in forest resources at the University of Minnesota.

"When seeds are ripe, they're only able to germinate within 7 to 14 days," said Nanninga, who is seeking funding to do further research on cottonwoods in greenhouses, where conditions can be more easily controlled.

"Cottonwood regeneration is a problem in the entire northern Great Plains," she said.

The fact that young cottonwoods aren't growing well here means the forests along the Mississippi River might someday look very different, said Katie Nyberg, the Mississippi River Fund's executive director.

"Many of the cottonwoods we're looking at right now, these majestic, beautiful cottonwoods, are really getting to the end of their lifespan," she said. That means the beautiful, classic view "of the floodplain forest that we all get to enjoy when we're out on the Mississippi River is in jeopardy."​