Cottonwood Trees

Occasionally we hear someone refer to grain elevators, sometimes rather disparagingly, as the skyscrapers of the prairie. But with the exception of grain elevators, the real skyscrapers of the prairie are cottonwood trees.

I was thinking about that the other day while driving across the state. It seemed that cottonwoods dominated the skyline of most every town I drove through. Out of curiosity I checked with the North Dakota Forest Service’s Champion Tree list for cottonwoods. The tallest tree listed is a cottonwood near Sheldon in Ransom County that tops out at 115 feet. I don’t know about the average height differences between cottonwood and other trees in North Dakota, but the record height for cottonwood is a good 15 feet above that for any other tree species listed.

The native habitat for cottonwood, as most people know, is floodplains, along streams

and shorelines, and wet meadows. The species has also had considerable use in plantings such as shelterbelts and in boulevards and yards.

However cottonwood is not viewed very favorably these days as a lawn or boulevard tree because the cotton can be a nuisance, the great height of the trees, and the characteristic of cottonwood to produce rather weak branches. As some of you may know, when one of those branches break it can do considerable damage to homes and other buildings.

Occasionally a student will ask why some cottonwood trees always produce cotton while others do not. Cottonwood is rather unusual in that they are dioecious, meaning the plant is either a male or female. It is the female trees that produce the cotton. Each little piece of cotton blowing in the summer breeze is attached to a very small seed.

If all goes well the seed will land on the ground where it will be constantly moist for the first few weeks and receive full sunlight. The seedlings are very susceptible to drying out and shading, so it takes quite specific conditions for seedling of cottonwood to become established. As you might surmise, spring flooding of rivers and streams is an important factor influencing the establishment of cottonwoods.

Check your town’s skyline; there is a good chance that it is dominated by cottonwood. Then, as summer commences you can identify the cottonwood Matriarchs from the Patriarchs.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.