Cottonwood Tree Guide: Identification of Eastern, Leaves, Seeds & More

Samson Opanda is an environmental engineer overseeing numerous sustainability projects in Kenya.Written by Samson Opanda

Forestry, Trees and Tree Planting | September 20, 2022

Close up image of cottonwood tree that show large green leaves and thick foliage in an oval frame.

The cottonwood tree is one of the most popular tree species in the world. Going by the scientific name Populus Deltoides, the tree originates from and is common in North America, growing in the US, Canada, and Mexico.

Read on to learn more about how to identify this beautiful tree…

The trees come in different varieties and are identified quite easily using their subspecies names. Cottonwood trees growing in southern Canada and the Eastern US come from the subspecies Deltoides, while those growing in the Southern part of Canada and the Central sections of the US go by the subspecies name Monilifera. The Wislizeni subspecies grows in the southern parts of Colorado, Texas, and Mexico.

All these subspecies of the cottonwood tree can grow to a height of up to 60 meters and a diameter of about 3 meters, making it one of the largest hardwood trees in North America.

For optimal growth, the trees grow around rivers and floodplains to access water.

Identifying the Cottonwood Tree

As noted earlier, the cottonwood tree has three different subspecies spread out across North America. The Deltoides subspecies grow in the southern-eastern parts of Canada and the Eastern parts of the US. Some of the notable areas include Ontario, Quebec, North Dakota, and Texas.

In comparison, the Monilifera subspecies grow in south-central Canada, the central US, and New Mexico. Cities in these areas include Manitoba and Alberta.

The final subspecies of the tree is termed Wislizeni. It grows mostly in southern Colorado, Texas, Mexico, and California. Identifying the cottonwood tree and distinguishing each of these tree species is quite a task. Fortunately, we’ve got you covered. In the next sections, we offer a guide on identifying the cottonwood trees and distinguishing their various varieties. We will start by looking at how cottonwood trees germinate and spread.

How Cottonwood Tree Seeds Germinate and Spread

As noted earlier, the eastern cottonwood tree grows mostly in the east side of the US, stretching all the way into Canada. The tree grows in a wide range of soil types. However, for optimal growth, well-drained soils along river banks are recommended.

The tree is also diecious, implying the male and female flowers grow on separate trees.1 Usually, the male flowers and buds grow earlier than female buds. They also tend to bloom much faster than their female counterparts.

The seeds of the tree develop in capsules hosted by short stalks. Under most conditions, the trees start producing seeds at the age of 5 to 10 years. Seed dispersal happens about two months after flowering. Water and wind are the seed’s main dispersal agents. Since most cottonwood trees grow around water bodies, the water medium and winds in such locations carry the seeds, dispersing them in the process. Unfortunately, the viability of the seeds is a bit low. To germinate, they must find moist seedbeds or be immersed in water, conditions that are not always readily available.

Nevertheless, the seeds can enjoy a germination rate of as high as 90 percent under the right conditions.1 These optimal conditions include sufficient sunlight to supply solar energy and soil moisture to supply water for photosynthesis. The growth of the seeds starts slowly.

Once the root zone is developed, the rate of growth is much faster. This fast and steady pace of growth is maintained throughout the tree’s lifetime. One feature of the tree worth noting that affects its growth is its shading tolerance.

In this regard, cottonwood trees are shade intolerant. They are one of the most shade-intolerant hardwood tree species, coming second to only the Black Willow.

Both of these trees grow in the same areas, competing for light and water. However, cottonwood trees tend to outgrow Black Willows, especially in stable water and sunlight levels1 Having discussed how cottonwood trees germinate, let’s now review how the trees look like.

What Do Cottonwood Trees Look Like?

Close up of the cottonwood tree flower resembles natural cotton.

Flowers of Cottonwood Trees

Cottonwood trees are easy to identify from their flowers, leaves, barks, and seeds. The male and female flowers grow on separate trees, a property identified by the term dioecious.2

The flowers are contained in about 3 inches of catkins. Each catkin has about 15 to 40 buds and is uniform in length. The flowers in the catkins appear before the leaves and are usually pollinated by winds.

The male flowers in the catkins protrude from the tree’s branches in clusters of about 2 to 4 inches. They are typically red and yellow with between 30 and 40 stamens. In comparison, female flowers are green and appear singly. Each female flower has a separate stalk.

Leaves of cottonwood trees

The leaves of cottonwood trees are triangular with a heart-shaped base that tapers to a long-pointed tip. They can grow to about 7 inches long and 5 inches wide and are shiny green on the top and slightly pale on the underside.2

The stalks of the leaves are long and slender, with two glands at the top. The heterophyllous property of the leaf is perhaps its most distinguishing property. Regarding this, cottonwood trees have two types of leaves; those formed during early winter and those produced later in the season.

The trees use the leaves that grow in early winter for early spring growth, while those growing later in the season are for full maturity. The leaves are distinguishable based on their size and number of teeth, with the former having smaller and fewer teeth than the latter.

The leaves of the cottonwood tree close up.

Barks of Cottonwood Trees

The barks of cottonwood trees vary in texture, color, and furrowed depth depending on the tree’s age. Typically, young trees will have smooth, shallow furrowed, light grey to yellow-green bark. 2

As the trees grow and mature, the bark’s color changes to gray and becomes rougher, and deeply furrowed. The twigs from the bark are brown and angled, with large buds of about three-quarter inches long. Green-brown resin scales cover the bark of the tree.

Seeds of Cotton Wood Trees

The seeds of cottonwood trees are formed after the pollination of flowers. Before fertilization, female catkins are about 6 inches long. Once fertilized, they produce elliptical shaped seed capsules that are initially green in color.

With time, the seeds turn brown, and the capsules split, releasing about 7 to 10 seeds. The seeds are usually attached to a white cotton-like thread that is easily dispersed by the wind.

Cottonwood trees start producing seeds at five years old, with their peak productivity coming at fifteen years.2 From that point onward, the trees will continue producing seeds for the rest of their life cycle.

Habitats of Cottonwood Trees

Cottonwoods grow in mostly riparian areas such as streams, rivers, and wetlands. The combined ecosystem of the cottonwood trees and marshlands offers an amazing habitat for different species of animals.

Some animals in this habitat include beavers, which feed on cottonwood’s tree barks, shoots, and stems. They also burrow holes into the trees to form their homes. Raptors, otherwise known as birds of prey, use cottonwoods as nests, while insects feed on the bark and other parts of the tree.

So vast is the biodiversity in cottonwood tree habitats that researchers estimate about 40 different animal species benefit from these trees.4 Other animal species in cottonwood forests include moose, deer, elk, insects, and birds.

The Cottonwood Tree Habitat’s Value to Plants

The Eastern cottonwood tree is by far the most predominant plant species in the flood plains of the US. The floods in these locations create ideal conditions for the growth of trees and other species.

Within these locations, cottonwood trees grow in pure and mixed stands. Other tree species that grow side by side with the cottonwood tree in these habitats include the white oak, black-berry, American hornbeam, and basswood. These riparian habitats that host cottonwood trees are also known to have common shrubs such as the Northern spicebush, black tupelo, and sand oak.8

Graminoid tree species in the habitats include wheatgrass, sand dune, switchgrass, and Indiana grass. These habitats are also known to have forbs (herbaceous flowering plant other than a grass) and vines. Common ones include the Asian bittersweet, poison ivy, trumpet creeper, and Virginia creeper.

Some cottonwood species grow in plains. In such habitats, tree species associated with the cottonwood tree include the green ash, American elm, and Russian olive. Shrubs in plain cottonwood habitats include the rocky mountain marple, douglas hawthorn, and Eastern wahoo. Graminoids in this location include the blue grama, Cheatgrass, and Canada wildrye. Forbs and vines include the Virginia creeper, pepper vine, and long root smartweed.

The Cottonwood Tree Habitat’s Value to Animals

Cottonwood tree habitats are exceedingly important for animal life. Eastern cottonwood trees are classified as having a fair value for most wildlife species, including songbirds, game birds, and game mammals.

For example, the northern Great Plains, which hosts eastern cottonwood trees, provides about 50 percent of deer habitats and 70 percent of the habitats for the sharp tailed grouse. Palin cottonwood regions support about 82 percent of the bird species in Colorado.8

More Cottonwood Tree Identification Tips: Identification Based on Local Names

As noted earlier, cottonwoods have three subspecies. In more casual terminology, these subspecies are termed Eastern Cottonwood, Black Cottonwood, and Fremont Cottonwood. Each of these tree types has a unique set of characteristics that sets it apart from the others.

The Eastern Cottonwood Tree

This subspecies is most popular in North America. The tree grows in riparian areas and is considered one of the softest hardwood trees in the region.

The Black Cottonwood

This subspecies grows mostly in rocky mountains. Also called the Western Balsam poplar of the California poplar, this tree is the largest type of Western Cottonwood.

The Fremont Cottonwood

This subspecies grows in California, Utah, Arizona, and Mexico. The tree is quite like the Eastern Cottonwood, save for the larger and fewer leaves and differences in flower and seed pod appearance.

Identification Based on Location

Another way to identify cottonwood trees is by looking at the ecological characteristics of the location of the trees. As noted before, cottonwood trees grow well in areas with sufficient light. The trees are the second most shade-intolerant species in North America.

They also require a lot of water. So much water that most cottonwood trees are grown in riparian areas such as rivers, lakes, and marshlands. Knowing these prerequisite conditions for the growth of the trees makes it easy to locate them.

For instance, in North America, the US’s Central, Eastern and Southwestern states have these conditions. It is therefore not surprising that most of the cottonwood in the country grows in these regions. Similarly, in Canada, cottonwood trees grow along the lakes and rivers in Ontario. Again, these conditions are favorable for the trees. Finding them in such locations is therefore predictable. By knowing the optimal conditions for the growth of the trees, identifying them is as simple as matching the conditions to a corresponding ecosystem.

Identification Based on Nearby Tree Species

Another way to identify cottonwood trees is by looking at the nearby tree species. A limited number of tree species can grow under the conditions favored for cottonwood trees. Therefore, by knowing which trees can grow under similar conditions to cottonwood trees and identifying them, locating cottonwood trees growing nearby is fairly easy.

For example, the black willow tree grows under fairly the same environmental conditions as cottonwood trees. In many locations, the two tree species compete for sun and water. Thus, by identifying black willows in a given site, one is also likely to find cottonwood trees nearby.

Historical Value of Cottonwood Tree: How the Kansas State Tree Got Its Name

Notably, cottonwood trees have more than just ecological value. They are also historical monuments. The story of the Kansas State Capitol – Cottonwood Tree illustrates the historical importance of the tree.

The cottonwood tree is one of the state symbols of Kansas, and is visible in old photos of the capital and the story of how a cottonwood tree became a city symbol is quite an interesting one.

One account provides that the cottonwood tree in the old photos of the Capitol grew in the east wing of the Capitol. It offered a much-appreciated shade for dignitaries of the city, including Benjamin Harrison and Vice President Curtis.

The Kansas Historical Society shares a much more reliable account. The story goes that T.J. Anderson moved to the city in 1865 and bought a house that faced the Capitol. At one point, he noticed a small tree of about three feet growing between some of the building’s stone. He and a fellow professor decided to preserve the tree even during the Capitol’s construction, and that is how it came to appear in the photos.

Fire would later ravage the Capitol’s cottonwood tree in 1882. In 1966 the tree experienced more damage, from the Topeka Tornado that happened that year. In 1983, the Secretary of State, Jack Brier, made several attempts to prevent the tree from collapsing.3 Despite all efforts, the tree finally collapsed at the end of that year.

Ancient Uses of Cottonwood Trees

As one of the native trees in North America, the Cottonwood tree delivered several benefits to the ancient communities of the region.5 Most native communities used the tree for religious practices. In particular, the native tribes of Pueblo and Navajo used the tree extensively in their spiritual practices.

Its roots were sometimes used to make Kachina dolls and other objects of worship used in traditional religious ceremonies. Other ancient tribes used the tree as a source of medicine. The community doctors would use the bark and leaves of the trees to make concoctions that many believed to have healing properties.

The uses of the tree went beyond religious and medicinal applications. Some native communities used the trees to make toys and dugout canoes for sea traveling. The large size of the tree’s trunk makes it possible to create such canoes, while the leaf’s shape makes it suitable for making toy whistles.

Others used the tree to make yellow dyes. The dye comes from the tree’s buds, which have chemicals that, once dried, produce the yellow pigment.

Some communities would even consume the seeds of the trees. The seeds have a sticky feel that gives a gum-like sensation that was a delicacy back in those days.5 Cottonwood trees continue to deliver these benefits and more today.

Modern Uses of Cottonwood Trees

The uses of cottonwood trees have since increased from their native applications. Presently, the tree is used primarily for making lumber and related products.6 The tree is suitable for such applications due to its moisture content and density.

In that regard, cottonwood trees have a very low moisture content of about 12 percent measured on a wet basis, and a light density of about 28 pounds per cubic foot.7 These properties make the tree light, but very strong… exactly what is needed for interior furniture applications.

Consequently, most lumber uses of the tree are limited to interior décor. The mentioned properties of the tree also make it exceedingly suitable for making wood pulp. Wood pulp has been increasing in popularity over the past few years. Cottonwood trees are used to make this pulp that is then used to produce high-quality papers for magazines and books. Important to note here is that the uses of cottonwood are limited to light applications, which, as stated earlier, are due to its low moisture content and light density.

In exterior furniture applications, using this tree is not recommended. Its light properties make it too fragile to carry the immense loads that exterior furniture typically carries. Other modern applications of the tree include usage in making food containers and packaging.

The Legacy of Cottonwood Trees in North America

Cottonwood trees are one of the most popular hardwoods in North America. The tree has several ancient uses, including making carvings used in religious festivals. Modern uses of the tree include mostly lumber and related products, where the tree’s low moisture content and light density is highly desired.

The trees are easy to identify by looking at their flowers, leaves, barks, and seeds, the details of which are covered extensively in this guide. Cottonwood trees also offer a habitat for various animal and plant species, some of which have been listed.

Beyond the mentioned benefits, cottonwood trees have historical value, too. Kansas uses the tree as one of its symbols, a metaphor for strength and longevity. With these tips for how to identify the trees based on their local names, location, and nearby tree species, you can start searching for these trees, and impress your friends with the subspecies.

These trees do more than all of this, though. As hardwood trees, they act as carbon sinks, meaning they suck a large amount of pre-existing carbon dioxide (CO2) out of the air. So, these trees actually have the power to not just slow down climate change, but actually reverse it with their carbon removal capabilities. It’s for this reason that the world needs to conserve these trees, to help them aid the Earth as a whole.


References

1Bottomland and Hardwoods. 2010. Web forest management guide. Accessed September 6, 2021. https://www.nrs.fs.fed.us/fmg/nfmg/bl_hardwood/eco/spechar/cottonwood_east.html.

2Friends of the Wild Flower Garden. 2013. Cottonwood (Plains Cottonwood). Accessed September 6, 2021. https://www.friendsofthewildflowergarden.org/pages/plants/cottonwood.html.

3Kansas Historical Society. 2021. Kansas State Capitol – Cottonwood Tree. Accessed September 6, 2021. https://www.kshs.org/kansapedia/kansas-state-capitol-cottonwood-tree/11746.

4National Wildlife Federation. 2020. Fremont Cottonwood. Accessed September 6, 2021. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Plants-and-Fungi/Fremont-Cottonwood.

5Nature at the Confluence . 2021. Learn About Our Amazing Cottonwood Trees . Accessed September 6, 2021. https://natureattheconfluence.com/learn-about-our-amazing-cottonwood-trees/.

6Pratima, Bajpai. 2018. Biermann’s Handbook of Pulp and Paper. Third Edition. Elsevier. https://www.sciencedirect.com/topics/engineering/cottonwood.

7Purdue. 2021. Cottonwood. Purdue University. Accessed September 6, 2021. https://www.extension.purdue.edu/extmedia/FNR/FNR-282-W.pdf.

8US Govt. 2021. Populus deltoides. Accessed September 7, 2021. https://www.fs.fed.us/database/feis/plants/tree/popdel/all.html.