Five years ago, Steve Stanton, Sr. planted two maple trees in his Alexandria yard in memory of his mother- and father-in-law. Now one is thriving and one is dying.
“It leafed out beautifully in the spring,” he said, looking toward the one that looks like it has mange. “Then it turned color and started dropping leaves.”
That was in June.
Across Minnesota, tree experts are hearing from homeowners whose cheery emblems of fall are in trouble. Instead of producing full, vibrant branches, some maple trees appear to be on their way to an early grave.
“Our native maples … as well as the introduced Norway maple and amur maple have been tanking all over the state for several years, but the past two have been particularly hard on them,” said Gary Johnson, a professor who specializes in urban and community forestry for the University of Minnesota’s Urban Forestry Outreach, Research and Extension office.
Douglas County Master Gardener Robin Trott pointed out challenges facing maple trees in a column she wrote for the Echo Press. Megan O’Neill, who works with the DNR’s forest health team in Bemidji, said she received a “handful” of calls about sickly maples in late July and early August, and that her counterparts in Brainerd and the Twin Cities have also taken queries.
One of her colleagues submitted samples to the state’s plant disease clinic which did not find any pathogen during their testing, O’Neill said.
“It was proposed that the symptoms could be due to environmental conditions over the winter, but this is just a theory,” she said.
A scan of news headlines over the past year report maple problems in other states, including Michigan, Washington and Virginia. However, tree experts say those problems could be completely unrelated to what is happening in Minnesota.
“I have received zero reports of maples declining in our natural forests,” said Brian Schwingle, a tree insect and disease specialist for the state. “I think that is highly noteworthy. Having said that, sometimes ornamental tree health concerns are the canary in the coal mine for forest problems.”
He added that he was not convinced that is the case in Minnesota.
If maple problems are isolated to yards, they could well be caused by the hard winter last year, southern seed stock not equipped for northern climates and urban stress, he said.
The issue does warrant further investigation, Schwingle said.
Maple roots also suffocate when soil becomes too soggy.
Tips for growing healthy maples, according to Schwingle and Johnson:
Don’t plant maple trees too deep, and keep them at least 60 feet away from roadways that receive de-icing salt.
Don’t use herbicides around the tree.
Only water mature maples during drought.
Before planting, test how well the soil drains. Dig a hole 24 inches deep. Fill with water and let completely drain. Fill a second time. The second filling should drain completely within 24 hours. If it doesn't drain well, plant silver maples instead of sugar maples.
Test soil for acidity. If the pH is 7.8 or higher, don't plant a maple.