Scientific Name: Populus angustifolia
This tree in Colorado Narrowleaf cottonwood is large shade tree native to the high plains and higher elevations (up to 10,000') of the Colorado and other Rocky Mountain states. It is not encouraged as an "urban" planting, however, in many of our higher communities, it is one of the more popular shade trees.
Hardiness Zones 3 to 9. A very hardy plant for the mountains and valleys of Colorado.
Growth rate Medium to fast growth rate depending on growing period. It can reach 50 feet in a 20 year period. Crown spread is around 30'. Branching habit is more upright than spreading. Pyrimidal at first and then developing a somewhat broader look.
Foliage Leaves are alternate; simple; ovate-lanceolate; 2"-3" long and 1/2" to 1" wide. Some think it is a willow leaf because of its slenderness and the fine serrated edges. Leaves turn a nice brilliant yellow in the fall. Petiole is not flattened laterally, a distinquishing characteristic. Winter buds are long and pointed and very gummy.
Flowers Short stalked catkins. Not showy.
Bark Smooth and light yellow-green when young, becoming shallowly furrowed on older trunks.
Insects and diseases The most common would be cytospera and bacterial wetwood.
Landscape value Best suited for open park areas. If planted along streets, a wide landscape strip or tree-lawn is needed. Narrowleaf cottonwood should only be used if no other large shade tree is available for the climatic condition. It is often used in high elevation or high plains windbreaks. Grow in areas where the crown will have adequate space. Mature crown diameter can reach 30-50 feet.
Michael Dirr, Manual of Woody Landscape Plants (University of Georgia, 1990)
Michael Kuhns, Trees of Utah and the Intermountain West (Utah State University Press, 1998)