Crested Butte is the wildflower capital of Colorado – Why here? 

Wildflower bloom near Crested butte last summer. (Photo by Bella Bionidni)

What role does the town of Mancos in southwestern Colorado play in our wonderful wildflower displays here in the Crested Butte area? A big one, it turns out. That’s because it matters what kind of soil the flowers have to grow in, and Mancos lends its name to a particularly rich bed in our mountains.

The town of Mancos contains what geologists refer to as a “type location,” where a particular rock formation (such as Mancos shale) has a consistent set of physical characteristics that distinguishes it from adjacent layers of rock and occupies a particular position in the layers of rock in a geographical region. A type location is where a rock formation was named, described, examined and often first mapped. 

Mancos shale can be found throughout the Intermountain West. To an untrained eye, it can look like a pile of dirt — not a particularly attractive layer of rock. Its outcrops often make up badlands in lower elevations where it typically is found. 

A relatively widespread and thick shale formation, the Mancos was deposited during the Cretaceous Period in a shallow interior seaway between 80 and 95 million years ago. It is approximately 4,000 feet thick in the upper Gunnison Valley. 

It is clay rich, soft, friable and breaks down very easily. It also weathers and decomposes into a very productive soil that can hold water and nutrients and with just the right amount of drainage. 

The Elk Mountains, where Crested Butte lies, contain an abundance of sedimentary rock, largely dominated by Mancos shale compared to other Colorado mountain ranges. 

These sedimentary rocks play a sizable role in why wildflowers are so diverse and exceptional here. Many other parts of the Colorado Rockies are dominated by soils sourced from granite and other hard rocks. These break down much more slowly and produce acidic soils of poor nutritional value. 

In the Crested Butte area, we have a high concentration of relatively young mountains which are igneous intrusions called laccoliths — Mount Crested Butte, Gothic Mountain and Whetstone, for example. Softer and less stable Mancos shale surrounds these laccoliths, forming the ideal locations for open meadows where wildflowers flourish.  

Aspens also thrive in the Mancos shale-derived soils. By contrast, conifers don’t have root systems that adequately support them in the Mancos shale, and they prefer the more stable granitic soils of the laccoliths and other igneous rocks in the Colorado Rockies. 

Aspen groves, with interspersed meadows provide desired sunlight for wildflowers to flourish and provide dappled light for other species such as columbines, geraniums, mariposa lilies and many others in their understories that prefer indirect sunlight. 

Another attribute of the Crested Butte area that supports our prolific wildflowers is the south and south-westerly exposure that dominates the Elk Mountains at the head of the Gunnison Valley. This aspect provides for the much-needed sunlight that wildflowers crave.

Why is Crested Butte the wildflower capital of Colorado? The answer lies beneath your feet.

(Jeff Delaney is a member of the Crested Butte Wildflower Festival board)