Cottonwood Trees

Cottonwood Trees

Cottonwood trees are the largest living things in Colorado, and the oldest living things on the Rocky Mountain’s Front Range. Only the bristlecone pines of Western Colorado are older, and they are the some of the oldest trees in the world. Our cottonwoods are such a familiar part of our landscape, that we often hardly notice them as we pass by them every day. They can get our attention though, such as in the spring when they release their seeds wrapped in “cotton”, or when a large limb falls unexpectedly. More often than not though, we rest in their shade in our parks, or on a hike on a hot day. 

There are three or four varieties of cottonwoods in North America. Here in Colorado, our native variety is known as Plains Cottonwood (Populus Sargentii). American cottonwoods appeared on this continent during the advance and retreat of the glaciers between 2.5 million, and 11,000 years ago, so the first people that walked here from Asia probably saw cottonwood trees much as they are today. Cottonwood seeds float far on the spring breezes, and float very well on the lakes and streams where they land. The seeds sprout and take root almost anywhere they can find enough moisture, such as along our lake shores and streams. Their roots go deep, and wide to find the water and nutrients to support their rapid growth.  Cottonwoods are closely related to poplars, aspen, and birch. 

The first people to arrive in North America had it rough. Much of the land may have been a cold desert, as much of the earth’s water was locked up in the glaciers. The habit of cottonwoods to grow very tall along waterways and lake shores may have helped these first arrivals to find water while walking across dry areas. You may have noticed that you can see a tall cottonwood from very far away. The only things taller than cottonwoods in Colorado are the mountains. 

Cottonwood leaves are rich in sugars and other carbohydrates. The leaves are good food for deer, elk, buffalo, and moose to eat. This means that when the First Americans spotted a line of cottonwood trees in the distance, it meant not only water, but also game, shelter from the sun, and fish in the stream or lake. In a pinch, when food is scarce, humans can eat the leaves or inner bark of cottonwoods. It does not taste very good, but it can keep you alive if there is nothing else. 

When Europeans arrived and began migrating west, the Great Plains and the Desert Southwest were challenging places to cross on foot, or by horse and wagon. Cottonwoods provided a beacon to show where there was water for themselves and their horses, shade from the sun, and dry wood for their fires. People who settled in the Great Plains used cottonwood lumber to build their houses and barns. Apparently, cottonwood lumber is very good for building barns and wagons, as it has a flavor that horses do not like, so that they do not “crib”, or chew on the wood as is their habit with other types of lumber. 

Building things with cottonwood lumber is not without its challenges though. When first cut, cottonwood is extremely wet. Leaving milled lumber out in the sun to dry causes more rapid drying on the sunny side than the shaded side, and the nice straight lumber quickly turns into something resembling a pretzel. The builders of Ft. Fremont discovered that the hard way when after cutting and milling the lumber to build the fort one spring, they left the lumber to season over the summer. When they came back in the fall to begin construction, they discovered that the nice timbers they had milled (using only axes, adzes, and other hand tools!) had bent and twisted in the sun so much that it could not be used. Cottonwood also decays very quickly when in contact with the earth, so that cottonwood fence posts rot and fall down within a few years. The settlers of the Great Plains and the Desert Southwest discovered that cottonwood lumber is much like any other lumber; it is great for some things, and not so great for others. 

People in Colorado today seem to appreciate cottonwoods much less than the First People to arrive, or the European settlers who came later. Our lives do not depend on the local environment as much as in previous times, and we tend to focus on the more annoying aspects of cottonwoods: The “cotton” from them clogs filters, gets in our noses, and is generally untidy. Cottonwoods often drop branches and limbs unexpectedly, causing damage to houses, cars, and even people. It is not used commercially any more for lumber, and it is not very popular even for firewood. These days, when our most ancient and majestic cottonwoods are cut down to make way for development, they are simply cut up into small pieces, and taken to the dump to rot.