Colorado Aspen Leaf Change - Autumn 2023
For most any Coloradan, aspen trees conjure up images of crisp fall days walking through groves of black and white bark and golden to red leaves that delicately rattle in the wind (hence the name quaking aspen). Here in the Southern Rocky Mountains of Colorado, aspens usually start to change their leaves beginning in September, with peak colors being observed in the middle of the month and continuing into early October (1). Besides the time of the year, latitude, elevation, local weather patterns (including drought or above average precipitation), and tree health also impact the timing of fall color changes (1).
This year, Colorado received more precipitation than usual so vegetation really took off. In fact, the snow this past winter and spring was enough to pull Colorado out of drought for the first time in four years (2). That’s pretty exciting! Experts with the Colorado State Forest say this contributes to better than average fall colors this year! In particular, if the growing season is wet (lots of snow and rain, which happened in Colorado this year), and autumn is sunny with cool, frost-free nights, then colors can be expected to be brighter (1).
So, going forward, how is climate change going to affect aspen trees and fall colors in the Rockies? It’s complicated, because this year’s conditions don’t align with the projected trend of Colorado becoming warmer and drier in the future, which stresses and kills aspen groves, but in general it seems that we can expect fall foliage to come at a later time in the year and stick around for a shorter period of time (3). However, brighter colors may also result, due to the warming temperatures which may equate to sunnier days in the fall (3).
In any case, I can confirm based off my sightings while camping and hiking this September and October, that the fall colors in Colorado are alive and well this year. Enjoy these photos of aspens (and some cottonwoods too) in Northern Colorado (Kremmling, North Park, State Forest State Park) and Golden Gate Canyon State Park.
On September 23, 2023, driving north of I-70 around Silverthorne, Dillon, and Frisco, I followed CO-9 north towards Kremmling. The valley here was full of aspens and also cottonwoods that were in their full gold regalia.
From Kremmling I continued north through Rabbit Ear's Pass and into North Park. This is also a beautiful area with lots of aspens, willows and other deciduous trees that were turning very yellow.
Finally, at the end of the day I reached my destination of State Forest State Park, and this is where the most spectacular color show was taking place (in my opinion at least). The finale was the sunset on the aspen trees facing the Never Summer Mountains in the distance (including the Crags).
Further south the following Saturday (September 30th), I ended up in Golden Gate State Park (west of Golden, near the Indian Peaks Wilderness). Aspen trees here were much further along, which speaks to how quickly the leaf changing season is in the Rocky Mountains.
References
- Aspen Fall Colors. Colorado State Forest Service https://csfs.colostate.edu/aspen-fall-colors/.
- Colorado’s fall leaf-peeping season could be one of the best in years. RMPBS https://www.rmpbs.org/blogs/news/colorado-fall-leaves/.
- As Colorado continues to warm, what happens to its famous fall foliage? RMPBS https://www.rmpbs.org/blogs/news/what-could-global-warming-mean-for-fall-foliage/.
To celebrate the fall colors this year in Colorado, and elsewhere in North America, I'm going to make a plug for the launch of a new iNaturalist project that I created: the Quaking Aspen Phenology & Fall Colors Project. If you love aspen trees or just enjoy observing changes throughout the year, join the project! Right now it is pretty casual but in the future I plan to add data fields for recording phenology pertaining to bud burst, leaf change, and leaf loss. (If anybody knows how to add additional project data fields on an iNaturalist project, let me know in the comments section).
Click on the link to join the project!
https://www.inaturalist.org/projects/quaking-aspen-phenology-fall-colors-project
