In March and April, park staff observe signs that spring is on the way. Aspen, one of the park's signature species, is blooming at lower elevations in the park. Many people do not recognize the blooms because they are catkins- the same type of fuzzy blooms as one sees on pussy willows. It appears the air temperature must be above 54° F for a period of about six days for flowers to appear. Flowers are wind pollinated. Aspen have male and female reproductive structures in separate flowers. The catkin is the female flower. Aspen, also known as quaking aspen, are a species of poplar (Populus tremuloides) and a member of the willow family.
Spring may be in the air as indicated by the aspen bloom, but winter took its toll on the trees as well. One of the first things visitors to Rocky Mountain National Park see when viewing some of the park's aspen stands is the large number of black scars on the lower portion of many trees. These are not signs of a disease, but rather are marks caused by elk eating the bark. Elk are not the only park wildlife that eat aspen. Beavers also enjoy them as a snack. Aspen have evolved with beaver and elk in the Rocky Mountains and can usually withstand a normal amount of wear and tear from these species. Aspen survival is usually threatened only in situations where there is an abnormally high concentration of these plant predators over a period of years. It is very common to see many new aspen sprouts popping up around trees that have been cut by beavers.
If you are interested in learning more about quaking aspen in general, or specific information about aspen flowers, we invite you to view the Forest Service's description of quaking aspen.