Cottonwood trees a water indicator in arid Colorado

A ribbon of water and adjacent land—known as a riparian ecosystem—is the lifeblood for many species of wildlife and flora. Cottonwoods are some of the most important riparian trees, and several species grow along the Arkansas River. They are members of the Willow family, along with aspen and the infamous willows that plague cross-country wetland hikers. Like all willows, cottonwoods are indicators of water—specifically riparian ecosystems.

High above Leadville, the Arkansas River starts its downward journey. Narrow-leaf cottonwood (Populus angustifolia) is found in places where the river flows down through montane and foothills life zones from about 10,000 feet to 6,000 feet. Narrow-leaf cottonwoods are medium-sized trees with lance-shaped leaves. They grow to a maximum of sixty feet, unlike their towering cousins on the plains.

Plains cottonwood (Populus deltoides) grows in the plains life zones below 6,000 feet or so. These huge trees, with their thick, furrowed bark and triangular shiny leaves, are familiar sights along the river.

The seeds and pollen of all cottonwood trees form in catkins, which are actually flower structures without petals. Male and female catkins are produced on different trees. The trees are named for the white fluff attached to their seeds and carried by the wind. Like the dandelion, this type of seed distribution, known as anemopholus, is extremely effective. Springtime brings a shower of cottonwood seeds—like an unexpected snowfall. Because the male trees have no seeds, they are popular among urban landscape designers. As a backup method of reproduction, cottonwoods can also sprout new shoots from stumps or branches.

The wood is soft, suitable for a wide variety of uses. Cottonwood artifacts from Navajo, Ute, and Arapaho Indians include many household items, among which are drums, weaving loom frames, bows, roof beams, and even snowshoes.

A variety of wildlife also use cottonwoods. It is reported in Canada that bees collect the sticky resin from cottonwood buds and young leaves to use in cementing and waterproofing their hives.