Denver’s fall colors are exceptional this year thanks to spring moisture

When Cheryl Spector goes for an afternoon walk on the tree-lined streets of her Park Hill neighborhood, she is moved by the stunning array of yellow, gold and dark crimson leaves that have made for an unusually beautiful fall color season along the Front Range.

“The late afternoon sun is weaving its way in between the leaves, highlighting and illuminating the yellows, the golds, and it’s almost like shining a bright light on the reds,” said Spector, an architect. “It feels like the trees are embracing you. Not only do you have the canopy above, but the leaves that have been released and are on the ground tickle your feet as you walk through them.”

Experts agree with what Spector and other tree lovers have observed anecdotally, that this is shaping up as an exceptional year for fall colors along the Front Range. They cite two reasons: good moisture when trees were leafing out in the spring — including a cool, moist June — and the mild temperatures of recent weeks.

“We’re actually having a very good year,” said Jeff Meyer, forestry inspections supervisor for Denver Parks and Recreation. “It’s one of the better years I’ve seen in awhile. I think it does have to do with the moisture we got earlier in the year. It was better for the trees than in recent years.”

Fall weather also has cooperated. On Sept. 8 last year, Denver saw a 50-degree temperature drop from the previous day with accumulations of snow. That adversely affected fall colors in the weeks that followed.

“We’ve lucked out this year with no early freezes,” said Kendra Boot, the city forester for Fort Collins. “We’ve had some normal drops in temperature, but they’ve been very gradual. In previous years when we’ve had less of a nice fall color season, we’ve had some pretty extreme temperature fluctuations, which shortened the amount of time the leaves stay on the trees.”

Extreme cold causes cells in leaves to freeze. “The leaves abscise (shed) from the tree,” Boot said, “and the wind helps to blow them off.”

That hasn’t been a problem this fall. Park Hill is flaunting glorious colors across an assortment of species. The cottonwoods along the Highline Canal in Cherry Hills Village are spectacular. Yet in some places, the change is just beginning.

“I was in Parker this weekend, and I live in Littleton,” said Meyer, for whom a white oak at Sixth Avenue and Holly that turns a dark crimson in the fall is his favorite tree in all of Denver. “I think we’re in the peak in some suburbs. Due to the heat island downtown, we are still looking forward to seeing a peak in the downtown area. Looking out over Civic Center, the oak trees are just now starting to turn yellow. But Parker was definitely in a peak. Autumn purple ashes are looking amazing.”

The timing of color changes is species-dependent, and almost all of the trees in Colorado’s urban areas are non-native species. Before the Front Range was settled, Meyer said, cottonwoods and perhaps some willows were the only trees in the area.

“Our native trees have definitely kicked in to the fall color,” Boot said of the cottonwoods that tend to line creeks, rivers and lakes. “They’re the ‘smart’ trees. They’re used to Colorado weather. Then we have a lot of non-native species in Colorado that we plant in our urban landscapes. Some of them take a little bit longer to deal with those temperature fluctuations.”

Boot says if gradual changes continue with fairly warm days but temperatures in the 30s at night, there may be several more weeks of fall colors. “We have a lot of trees that still look like it’s the middle of summer, pretty green,” Boot said.

In Park Hill, Spector said, the big change commenced with last week’s cold snap.

“It’s been warm,” Spector said. “Generally it’s the combination of the cold and the change in sunlight that gets those leaves starting to go. I think they’ve been a little bit slower to initiate their change. Then last week, we finally had some cold weather. That was like, ‘boom!’ They’re like, ‘OK, it’s time.’ ”

Spector is a specialist in biomimicry, a practice that takes inspiration from nature to solve human problems. When she admires fall colors, she feels a connection to the trees transitioning into dormancy.

“You feel embraced,” Spector said. “I think that gets to the turning of the season. We feel the change in the sunlight, whether we are conscious of it or not. It’s this turning within, just like the trees that are releasing their outward canopies, dropping their leaves and turning within to build up their reserves through the winter.”

“Late afternoon, the light is just perfect,” said Sara Lemmon, another Park Hill resident. “It reflects off of the trees creating vibrant hues of reds, yellows and purples. Walking through the neighborhood at this time gives me a sense of calm — like no matter what happened during the day, the world is still full of magic and beauty. Just look at the trees.”

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