Perhaps when looking at the hillsides now, you will see a stand of trees off in the distance that appear to be covered with white blossoms. However they are not blossoms. You are looking at a stand of female aspen trees unfurling their leaves.

During the middle of April, the catkins on the male aspen trees seemed to appear overnight. After a long winter, I always welcome the emergence of the male aspen tree’s catkins as a sign that spring is near. The male catkins are a good indication that spring has finally arrived, even though the grayness and dampness of the air might suggest otherwise.

At that time, we were able to look at the mountain side and pick out stands of male aspen trees. This was because the catkins hung down from the branches, and from a distance, the bare trees appeared to be white. The catkins, which emerge before the leaves, are cylindrical in shape and fuzzy, with feather-like tufts of hair adorning numerous tiny seeds.

These male flowers appear long before the leaves. The leaves on the male aspen trees will begin to appear near the first of May while the female aspen trees will still be in their winter buds.

The male and female flowers of the aspen trees are produced on different trees. The female catkins 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 the other trees that have already leafed out. However, at this time, the female aspen trees are leafing out, with their leaves showing white. These trees can 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. The leaves on vigorous sprouts can be four to five 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 located 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 are 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 40-100 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, and for this reason is considered to be an indicator of ancient woodlands.

One such colony in Utah has been given the nickname of Pando (a Latin word meaning, “I spread”) and 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 can photosynthesize through its bark. Although the bark somewhat 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, hence, the name trembling aspen.

The aspen tree has little value except to the beavers which consider it their favorite food.