The Cottonwood Tree

What Is the Largest Flowering Plant Found in Wetlands Park?                         

Towering to 90 feet or more, the stately Fremont cottonwoods (Populus fremontii) are Clark County Wetlands Park’s tallest trees. Cottonwoods are dioecious, meaning that both male and female trees “flower.” This happens between February and May. Pollination is by wind: mature male catkins “land” on the female trees’ catkins, resulting in fruits that are either rounded or ellipsoid capsules. When mature, the fruits burst, and seeds disperse on cottony hairs in the wind. The tree’s name comes from the fluffy, cotton-ball appearance of groups of seeds found on the ground and other places.

Mature cottonwood trees have rounded tops, triangular or heart-shaped leaves with lobed margins, and thick, gray, furrowed bark. The leaf petioles (leaf stems) are laterally flattened (like a knife blade) rather than round, which allows the leaves to flutter in a breeze. Native Americans have historically revered the cottonwood, attributing the resulting rattling of leaves in the wind to a spiritual power. In the late winter/early spring, fallen twigs feature knobby bud scale scars (spots where leaves grew seasons before). When snapped, the stems reveal reddish-colored star shapes in their center (pith). This “star” adds more symbolism to Native American belief systems, from using cottonwood branches in Sun Dance ceremonies (the tree of life) to calling upon the Wind Spirit to send the stars (found inside the twig stems) to heaven.

Cottonwoods are found in riparian habitats—those lush, highly “green” areas adjoining aquatic habitats. Riparian habitats provide optimal living conditions for a diversity of wildlife. The trees contribute to supporting different groups of animals occupying or using the different layers of vegetation. This multi-story “canopy” arrangement is often present nowhere else in arid landscapes.

Mammals associated with these trees include raccoons, squirrels, ringtails, beavers, and other rodents. Raptors, including eagles, owls, and hawks, use the trees for nesting, protection, and perching while hunting prey. The large trees also provide habitat for cavity-nesting birds, perching birds, and woodpeckers. Great blue heron’s also benefit from these large tree communities. Aphids tap into the cottonwoods’ sweet nectar; worker and farmer-type ants harvest the nectar from the aphids.

As small seedlings, the trees require proximity to water at ground level and as they develop and mature, they need water sources to tap below ground. The cottonwood stand found in the central part of the Park’s Nature Preserve generally has access to both. Canopies of these trees growing on streambanks (such as those in the Pabco Trailhead area) provide shade and  cool stream water, while their roots stabilize and create overhanging banks, providing habitat for fish and other aquatic organisms. In the fall, the cottonwood leaves turn a delightful yellow color before turning brown and falling to the ground.

Native Americans discovered numerous ways to utilize the cottonwood. Its sweet and starchy sap can be consumed raw or cooked. While the bark is bitter, it is edible. It can be scraped off and eaten, cooked in strips like soup noodles, or dried and powdered as a flour substitute. The inner bark of cottonwoods was used to feed man and horse in hard times. Some Indians preferred it because of its sweetness.

A cottonwood tree has also been used a “pharmacy” for people.  Cottonwoods contain two active medicinal constituents: salicin and populin, precursors of aspirin that are helpful for reducing fever or inflammation. The bark is the most effective part for making medicine but is rather bitter; for this reason, a tea made of cottonwood leaves was often preferred for internal use.

Such teas have also been used as diuretics, to assist with indigestion, aid coughs from colds, expel worms and intestinal parasites, and to treat scurvy, heart troubles, back pain, excessive menses, and urinary tract infections.

In the spring the cottonwood’s leaf buds were used to make an excellent ointment for burns and skin irritations. A wash (or tea) of the bark was applied externally for cuts, bruises, abrasions, burns and fetid perspiration, as well as healing chafing sores on horses. A wet compress of the tea can be used for sprains, muscle pain, and swollen joints. A lotion can be made that cleanses and conditions the skin when used regularly.

Next time you’re in the Park in the spring and summer, locate a riparian area and make a visit. There, close your eyes in the cool shade and listen. Do you hear the rustling of the cottonwoods? If you do, I hope you remember the many fine benefits of these remarkable trees.

– By Constance Carlson; photo by Crystalaura Jackson

Please enjoy these YouTube videos:

Fremont Cottonwood (Populus Fremontii) Great Clark County Wetlands Park video on “fluff”

Fremont Cottonwood (Populus Fremontii)

Populus fremontii (rachel spaeth)