An unusually cool and wet start to the summer pushed much of Colorado out of drought – and has also created conditions that could lead to some of the most vibrant mountain fall colors in years.
“We’re going into this season looking really good; the aspen stands are greener than I’ve seen in quite some time, and it looks like everything’s setting up perfectly to have a really good aspen show across much of the state,” said Dan West, an entomologist for the Colorado State Forest Service.
Sometimes, excess moisture might actually lead to below-average leaf seasons since it allows the fungal spores that infect aspens to germinate once it gets warmer. However, West said this year there was never enough sustained heat for these pathogens to thrive, which means that the leaves in the mountains are going into the fall healthier than they’ve been in years past.
West said the leaf season depends on conditions staying sunny during the day, and nights staying crisp and cool – but without frost that kills the leaves.
“Here’s how it works: the bright sunlight burns off the green colors, and then those underlying yellow and orange hues start to really show through as the nights get longer and colder,” West said. “The factors that really can impact the aspens are frost, wind and those early mountain snows.”
The team at the Colorado Climate Center says early fall conditions are trending toward warm and dry, which bodes well for leaf season.
“It’s shaping up to be a wonderful year to go out for a drive or a bike ride or anything else where you get to enjoy the fall season,” West said.
When will the leaves peak?
The leaf season typically happens in Northern Colorado in mid-to-late September, with the southern parts of the state peaking in late September to early October. However, West said this year, there could be some variation in the timing in the southwestern corner of the state, which remains in a drought.
West said this could cause the aspens to delay the onset of color, but he predicts they could also turn a little bit earlier because of the lack of precipitation.
“We’ll have to wait and see what the situation looks like in the coming weeks,” West said. “For the rest of the state, I anticipate that we’re going to have a relatively average year in terms of our timing.”
The Front Range did have sustained hot conditions this summer, allowing pathogens that affect cottonwoods to thrive and leaving some leaves dry ahead of the fall season.
But West emphasized that the aspen groves in the mountains should put on a good show – as long as there are no powerful wind storms or sustained frosty nights. He also said that drought conditions in the past may have given leaf-peepers different expectations, so he encourages people to be flexible.
“If you always go to the same area and it’s not as great as the year before, continue on, because looking at the state as a whole, the aspens are looking really, really good,” West said. “I don’t think anyone will be disappointed.”