Lack of moisture turns leaves early
Fall isn’t here yet but the season’s hues have raced ahead, dotting Bigfork’s green canopies with reds and yellows. Trees around the area have started to turn color and the summer’s lack of moisture may be the reason.
Melissa Jenkins is a silviculturist with the Flathead National Forest. While several things could be responsible for color change, Jenkins said spotting the same effect across species narrows the list.
“When something is happening to lots of different species of trees in a wide area, it’s typically not an insect or disease, it’s environmental,” Jenkins said.
She pointed to below-average precipitation as a strong possibility. Jenkins explained many trees have tiny openings, called stomata, on the bottoms of their leaves. While the openings allow trees to gather material for photosynthesis, she said they also allow water to evaporate.
The summer’s lack of rain left trees dry but Jenkins said heat compounded the problem by increasing evaporation. This means trees need even more water while having access to less. One solution, Jenkins said, is to lose what’s losing water: leaves.
Most trees have already made their winter food so losing the leaves, their food makers, would be the better than going thirsty. The color change comes when the plant stops producing chlorophyll.
“It’s their way of dealing with it,” Jenkins said.
“It’s really a good thing in the end because they’re more likely to survive this dry period.”
Northwest Montana is currently listed at a D3 drought level by the United States Drought Monitor. Also known as extreme drought, the classification is based on several measures of moisture in the area.
Jeff Kitsmiller, meteorologist with the Missoula National Weather Service, said numbers showcase how dry it is. On Aug. 11, the Kalispell weather station had recorded 6.72 inches of moisture in 2015, well behind the yearly average of 10.9 inches. The month of June was two inches behind its average and July was one inch behind.
Mary Thompson doesn’t know if she can make up for all that missing rain at Swan River Gardens.
“Sometimes I wonder if you can throw enough water at these plants,” she laughed.
As nursery manager, Thompson bumped watering from once to twice a day and hand watering from once a week to every other day. It was a big increase but with low precipitation and humidity, Thompson said there wasn’t a choice if they wanted to keep leaves from drying out.
Brad Brown has fought the same drought stress in his trees. Brown is owner of Glacier Nursery, Inc., a wholesale business that grows a variety of trees as part of its stock.
“I saw the very first signs of it on the Fourth of July in the field,” he said.
Brown has noticed that stress compounding on his trees and now sees leaves turning three weeks ahead of time. He explained the process, usually dictated by decreasing daylight, is now being dictated by a lack of moisture.
“It’s a natural process you just kind of roll with,” he said.
Brown knew his trees would survive but advised anyone experiencing the color change to do one last deep watering mid-October. He said extra moisture before the first freeze would help plants survive winter.
Pat McGlynn, Flathead County MSU extension agent, also recommended a good watering but added people should be careful how they water. She said lawn irrigation only reaches two or three inches down, not deep enough for a tree.
McGlynn said the best way to water is to place a soaker hose on a tree’s “drip line” for several hours.
She clarified that a drip line is not irrigation hose but a horticultural term. It refers to the ground area under the outer circle of a tree’s branches. This is where the feeder roots that can absorb water are.
To find a drip line, McGlynn said to imagine the canopy as an umbrella and the circle made by that umbrella’s edge as the drip line.
Even with water, a tree may change color early but McGlynn stressed the change wasn’t a bad indicator.
“If they were to shut down now, they would be okay,” she said.