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The science behind the fall colors in Missoula

Fall Foilage Missoula
Fall Foilage Missoula
Fall Foilage Missoula
Posted at 9:48 AM, Oct 05, 2022
and last updated 2022-10-05 11:48:09-04

MISSOULA - The greens, the reds, the oranges and yellows are all an indication that autumn is here — but as a Missoula arborist explained, there are a few factors that determine when and into what color these leaves will change.

“Right now I’m leaning up against the Montana state tree, the ponderosa pine,” City of Missoula Urban Forestry Program Specialist Marie Boggess said. ”Really cool thing about these, when the sun shines on their bark they smell just like butterscotch cookies.”

Similar to the state tree, Montana has some sweet views during the fall and a few factors give trees the green light to change the color of their leaves.

Fall Foilage Missoula

“It’s really going to be a factor of daytime temperatures, in the 60s and overnight when it drops down into the low 40s and starting in the 30s, that’s when we’re really going to see the chlorophyll dying off in the leaves and those yellow, orange and red pigments shining through,” explained Boggess who has been a certified arborist with the City of Missoula for 16 years.

If you’re seeing the leaves change before temperatures drop, Boggess says that may be the sign of a problem.

“A lot of the trees that we’re starting to see turning earlier in the fall, it’s really not a function of the tree’s natural process of going dormant. It’s trying to save itself because it’s not getting enough water.”

Boggess says a lot of trees are seeing drought partly as a result of climate change and because soils in Missoula don’t have a high-water holding capacity.

“You know the flooding, as it took away all that soil, it left behind a lot of rock and cobble and so the trees don’t really have enough resources.”

Fall Foilage Missoula
A Missoula arborist explains there are a few factors that determine when and into what color the leaves will change.

And if smokey conditions are “extraordinary,” Boggess says it can impact fall conditions as we know it.

“If we’re getting a lot of smoke, that actually can make the leaves change quicker. Just because they’re not getting as much sunlight filtering through”

She said we really dodged a bullet this year because the smoke wasn’t that bad. But even in smokey conditions, the trees are still clearing the air.

“It doesn’t really have that much of an impact on leaves other than the leaves filter that air for us, so they really do help reduce some of that particular load in the air,” Boggess told MTN News.

Boggess says you don't have to be an arborist to help the environment.

Marie Boggess
City of Missoula Urban Forestry Program Specialist Marie Boggess

“Another way when [people] are cleaning up their leaves in the fall, to mulch them and keep them on site, so those nutrients can go back into the soil profile and will be available for the tree as those leaves break down.”

Her favorite place to view the leaves changing colors is the M trail, but there’s another trail that’s just as highly recommended and now more accessible.

“Through the 2018 open space bond, we were able to do an ADA-accessible trail on Waterworks Hill where it has a new parking lot. It has new drinking fountain features and it’s accessible to anyone. It’s another great place to see the leaves turn,” Boggess concluded.