Wyoming State Tree: Plains Cottonwood

Wyoming recognizes the Plains Cottonwood as its official state tree. This deciduous hardwood typically grows 50 to 80 feet tall along Wyoming rivers and streams, though protected specimens near permanent water can exceed 100 feet. The trunk measures two to four feet in diameter at maturity. Wyoming's cottonwoods grow rapidly when young, sometimes adding five feet of height annually. This fast growth made cottonwood valuable to Wyoming pioneers who needed building materials and shade quickly. The tree provided lumber for cabins, barns, and corrals across Wyoming when other timber required hauling from distant mountains.

Cottonwood grows exclusively near water in Wyoming's arid landscape. The species lines the North Platte, Green, Snake, Powder, Bighorn, and Yellowstone rivers along with countless smaller streams. These riparian corridors create green ribbons of vegetation through Wyoming's otherwise brown plains and sagebrush basins. Cottonwood groves mark water sources visible for miles across Wyoming's open country. The trees require permanent groundwater, making them indicators of reliable water—information that guided Wyoming settlement patterns. Where cottonwoods grew, pioneers knew they could find water for themselves and livestock.

Wyoming contains relatively few tree species compared to forested eastern states. Most of Wyoming consists of high plains, sagebrush basins, and mountain ranges where conifers dominate above 7,000 feet. Cottonwood is one of the only large deciduous trees that thrives at Wyoming's lower elevations. The species tolerates Wyoming's temperature extremes, surviving winter lows below -40°F and summer highs above 100°F. Its adaptation to Wyoming's harsh continental climate and its prominence along every major river made cottonwood the obvious choice for state tree in a largely treeless landscape.

The common name is Plains Cottonwood, though many Wyomingites simply call it cottonwood. The scientific name is Populus deltoides. Populus is Latin for poplar, the tree family to which cottonwood belongs. Deltoides refers to the delta-shaped or triangular leaves. The subspecies found in Wyoming is typically monilifera, the plains form that grows throughout the Great Plains and Rocky Mountain region. This species belongs to the Salicaceae family, the willow family.

The name cottonwood derives from the cottony seeds that fill Wyoming air each June. Female trees produce capsules that split open, releasing thousands of tiny seeds attached to white cottony fibers. These fibers help seeds float on wind and water, dispersing far from parent trees. The cotton accumulates in drifts along Wyoming streets and buildings, creating snowlike conditions during peak seed release. Early Wyoming settlers called this tree sweet cottonwood to distinguish it from the bitter cottonwood or black cottonwood found in Wyoming's mountains.

Wyoming named the Plains Cottonwood as its official state tree on January 31, 1947. The Wyoming Legislature passed House Bill No. 56 during the 1947 legislative session. Governor Lester C. Hunt signed the legislation establishing the cottonwood designation. The bill passed with broad support from legislators across Wyoming's rural counties. These representatives understood the cottonwood's importance to their constituents who lived and worked along Wyoming's rivers where the trees grew.

Wyoming picked plains cottonwood because it represented survival and settlement in harsh conditions. The tree provided pioneers with essential resources in a landscape lacking forests. Cottonwood logs built the first cabins along Wyoming rivers. The wood, though soft and prone to warping, served when nothing else was available. Cottonwood shade offered relief from Wyoming's intense summer sun on the open plains. Livestock gathered beneath cottonwood groves during hot afternoons. The trees marked reliable water sources and good camping spots along emigrant trails. Oregon Trail travelers carved their names in cottonwood bark at Fort Laramie and other Wyoming landmarks. These historical associations made cottonwood meaningful to Wyoming residents.

The tree's native status and adaptability influenced the selection. Plains cottonwood evolved in Wyoming's environment and required no human assistance to thrive. Unlike ornamental trees that needed irrigation and care, cottonwood flourished naturally wherever groundwater reached near the surface. The species already grew along every significant Wyoming river before white settlement. Native Americans used cottonwood bark to feed horses during winter when grass was unavailable. The inner bark provided emergency food for humans during harsh times. By 1947, cottonwood had supported life in Wyoming for thousands of years. The designation honored this long history of service to people living in Wyoming's challenging landscape.

Wyoming's state flower is the Indian Paintbrush (Castilleja linariifolia), designated in 1917. The state adopted its floral symbol three decades before selecting the plains cottonwood. Both the Plains Cottonwood and Indian Paintbrush represent Wyoming's native flora adapted to harsh conditions. The bright red-orange paintbrush blooms across Wyoming's sagebrush plains and mountain meadows each summer. Cottonwoods grow in valley bottoms along rivers while paintbrush covers the higher plains and slopes above. These species occupy different Wyoming habitats but share the toughness required to survive the state's extreme climate. Together they represent Wyoming's diverse landscapes—riverside oases and windswept uplands.

The bark provides clear identification on mature trees. Young cottonwood bark appears smooth and yellowish-green to light gray. As trees age, the bark develops deep furrows creating thick, rough ridges. Mature bark is gray to gray-brown with a deeply fissured texture. The ridges form a distinctive diamond or rectangular pattern. Old cottonwoods display very thick bark with deep crevices—bark thickness protects against prairie fires that historically swept Wyoming grasslands adjacent to river corridors.

The leaves offer definitive identification during Wyoming's growing season from May through September. Each leaf has a distinctive triangular or delta shape with a pointed tip. Leaves measure two to four inches long with coarsely toothed edges. The leaf stalk or petiole is flattened, causing leaves to flutter and shimmer in Wyoming's constant wind. This movement creates the rustling sound characteristic of cottonwood groves. Upper leaf surfaces appear shiny bright green while lower surfaces show lighter, paler green. In autumn, cottonwood leaves turn clear yellow, creating brilliant displays along Wyoming rivers before falling in late September or October.

The overall form shows a broad, spreading crown with massive horizontal branches when growing in open riverside locations. Trees develop thick trunks that often lean at angles, reflecting Wyoming's persistent winds and periodic flooding. The bark frequently shows deep scars and wounds from ice damage during spring breakup when ice floes batter trees along riverbanks. In June, female trees become covered with cottony seed masses that drift through Wyoming air like snow. This cotton provides an unmistakable identification feature, though it appears only on female trees. Male trees produce reddish catkins in spring but no cotton.

The Plains Cottonwood symbolizes water, life, and survival in Wyoming's arid landscape. The tree represents the essential connection between water and existence in the high plains. Its presence marks reliable water sources that determined where people and animals could survive. For Wyoming pioneers, cottonwood groves meant shelter, shade, and hope in a harsh environment. The tree's ability to thrive despite Wyoming's extreme temperatures, wind, and drought embodies the resilience required to prosper in challenging conditions. Modern Wyomingites view cottonwood forests as precious riparian corridors that support biodiversity in otherwise sparse landscapes. Conservation of these riverside groves reflects Wyoming's understanding that water, trees, and life remain inseparably linked across the state's plains and basins.