The aspen tree (Populus tremuloides) has long dominated much of the American West with its glowing white bark and brilliant yellow fall colors. The trees' average life span ranges between 100 to 200 years when planted in its wild habitat, but when utilized as a landscape tree, most quickly pass away before they turn 25. The tree averages 120 feet in height with a diameter of 54 inches when fully grown. The wood is often harvested for flakeboard, fiberboard, animal feed, biofuel and sawtimber.
The aspen tree is dioecious, which means it is self-fertile. The tree produces both male and female flowers. Despite the ability to produce both sexes, most trees appear to be either predominately female or male with a more abundant flower production of one sexual flower. Each spring, from April to May, 2-inch-long catkins appear on the tree. The temperature must remain above 54 degrees F for at least six days in a row in order for flower production to commence.
Every four or five years the aspen produces abundant seeds but other years seed production is sparse. Seed crops begin when a tree is between 2 to 3 years of age. The production increases over the years. Maximum production normally occurs between 50 to 70 years of age. The seeds are dispersed by the wind. It is believed that at least 95 percent of all the seeds are viable according to the U.S. Forest Service. Unfortunately, the viability only lasts two to four weeks.
The aspen tree also produces suckers which grow into seedlings. This accounts for the relatively large groves of aspen trees that are found clustered together. The soil must retain a temperature of 74 degrees F for sucker growth to flourish. Forest fires often destroy parent trees but the sucker growth survives. In areas of clear-cut the suckers also grow with added vigor.
Pests and Disease
Aspen trees suffer from numerous pests and diseases. Animals also cause ongoing damage. Beavers, dear, meadow mice, elk and moose all girdle trees which often results in its death. Both Venturia macularis and Colletotrichum gloeosporioides cause leaf damage to young stands. Rust fungi also pose a serious problem to aspens. Numerous canker diseases are prevalent. More then 300 species of insects are common pests of the aspen tree according to the U.S. Forest Service. Most do minimal damage.
Aspen Tree Death
In 2006, aspen trees across many Western states began to die. The demise of entire groves has become widespread and scientists are still studying the reason why the deaths are occurring. Many believe that drought conditions have made the stands of older trees more vulnerable; others point to climate changes as a cause and many believe that it's a natural cycle, according to Colorado State University.