Diary entry April 14, 2014: "The catkins on the male aspen tree seemed to have appeared overnight."
After a long and cold winter, one welcome sign of spring is the emergence of the male aspen tree's catkins, or flowers. This is a good indication that spring has finally arrived, even though the grayness and dampness of the air might suggest otherwise.
Diary entry April 27, 2014: "I'm now able to look at the mountainside and pick out stands of male aspen trees."
PHOTO COURTESY OF BILL BOWER
On male aspen trees, the catkins emerge before the leaves are cylindrical in shape.
The catkins, which emerge before the leaves, are cylindrical in shape and fuzzy, with feather-like tufts of hair adorning numerous tiny seeds. They hang down from the branches and, from a distance, the bare trees appear to be white.
The male flowers, called staminate, appear long before the leaves.
Diary entry May 5, 2014: "I checked the male aspen trees today and noticed that the leaves are unfurling. I also checked the female aspen trees, and they are still in their winter buds."
In the aspen tree, male and female flowers are produced on different trees. The female catkins, or pistillate, will appear when the male catkins are ready to spread their pollen.
After the wind has blown the male's pollen over the female catkins, the female catkins will ripen.
By the end of May, the male aspen trees have leafed out and will blend in with other trees that have leafed out.
However, at this time, the female aspen trees leaf out. With their leaves showing white, the trees are able to be seen from a distance. The leaves are sometimes referred to as silver dollars.
Young leaves of the large-toothed aspen are white and appear somewhat downy. Those leaves on vigorous sprouts can be 4 to 5 inches broad and will remain the same color and downy beneath.
The condition of a tree when it is either a male or female is known as dioecism. While both male and female aspens produce catkins, only the male catkin has pollen, which is transferred to a female by the wind.
After the right breeze comes along, in early summer, the pollinated female will release her seeds, which are parachuted through the air and swept away to some distant place.
Aspens have a low rate of reproductive success. Each year it takes trillions of seeds dispersed by the wind to ensure that enough seeds are distributed and land in a suitable environment, where they can germinate and sprout.
Reproductive success is limited in part because aspens have strict germination constraints. For example, aspens are shade-intolerant, meaning that a seed needs a sunny spot to grow. Also that spot must be able to retain moisture and be free from seed-eating birds and animals.
The aspen tree also reproduces from suckers sent up from the roots. If a forest fire occurs, the heat of the fire causes dormant buds under the bark of the roots to send up a sprout.
The roots that send up these sprouts extend well over 60 feet away from the tree. When the roots near the surface of the soil, the suckers break through the ground. This type of reproduction is called coppice.
Each individual tree can live from 40 to 100 years above ground; however, the root system of the colony is long-lived and could live for thousands of years, sending up new trunks as the older trunks above ground die off. For this reason, it is considered to be an indicator of ancient woodlands.
One such colony in Utah, which has been given the nickname of Pando (a Latin word meaning "I spread") is estimated to be 80,000 years old, making it possibly the oldest living colony of aspens.
On older trees, the bark of the trembling aspen is a pale white but, when wet, the bark tends to appear green. This is because the aspen tree is able to photosynthesize through its bark. Although the bark resembles that of a white birch tree, it is unlike the birch tree because the aspen's bark does not peel.
On older trees, the bark near the base becomes thick, furrowed and nearly black.
The leaves have ribbon-like leafstalks, which are longer than the leaf and flattened to the plane of the leaf, that cause the leaf to turn in even the slightest breeze.
After moving to Bradford County, in the spring of 1969, my wife, Mary Alice, developed an allergy to something that bloomed in May. I always blamed it on the aspen trees because her allergy coincided with the males spreading their pollen.
Through the years, her body has become accustomed to whatever she was allergic to, and although she still has the sneezing and the red watery eyes, it is not nearly as bad as when we first moved to the area.
Bower retired after 34 years as a wildlife conservation officer for the state Game Commission. He has published several books about his experiences. Questions and comments may be sent to him at 153 Redington Ave., Troy PA 16947.