Door to Nature: Aspens Make Their Own Music

This time of year we enjoy lingering at the top of the Hibbard’s Creek valley near our home and drinking in the brilliant yellows of the trembling aspens that do so well in the creek bottom. We look at their beautiful late fall show as the quiet subtle “afterglow” following the more vibrant mid-October colors of the maples.

A part of our fun recently, as we hiked along the base of the Niagara Escarpment through adjacent fields and thornapple thickets at the top, was enjoying both of the aspen species native to this region. Many of the one- to two-inch thin, papery leaves of the trembling or quaking aspens still clung tightly to the twigs, producing a gentle rustling “conversation” on this pleasant sun-drenched afternoon.

Large-toothed aspen leaves can be quite colorful in autumn.

I especially like the name trembling aspen because it speaks of its scientific name, Populus tremuloides (trem-you-low-EYE-dees). Populus is the classical Latin name of this large group of related trees while the tremulous action of its leaves brought about its species name.

How well I can recall our family trip around 1935 to visit my mom’s Aunt Inga and her son Russell in the Upper Peninsula of Michigan where he made a living cutting and selling what they called “popple” to the paper mill. Most people of our general region refer to this common tree as either the quaking aspen or popple.

One of the reasons so many people enjoy the trembling aspens is because they retain their bright yellow leaves so late into the fall. However, a hard rain or stiff wind often causes an earlier than usual drop of some of the leaves. Such is the case in the small aspen grove west of our house. The path through this grove, leading to our garden, is liberally decorated with bright yellow leaves, round like fallen gold coins.

Many people look down upon the lowly aspens as just plain good-for-nothing. However, don’t tell that to the beavers. The bark, especially the nutritious inner bark, makes up much of their winter food, and the twigs, branches and trunks are also used in the construction of their lodges or dams.

Ruffed grouse, snowshoe hares, porcupines, moose and deer all depend upon either the buds, bark or leaves for food. The grouse favor the more nutritious buds on male trees that are around 40 years or older. Yes, aspens are either male or female and are said to be dioecious (dye-EE-shus).

Leaves of the large-toothed aspen, Populus grandidentata (gran-di-den-TAY-ta), are about twice the size of those of the trembling aspen and have very coarse teeth along their margins compared to the very small and fine teeth of the trembling aspen. Outwardly the trees appear similar.

Once leaves of both trembling and large-toothed aspens have fallen the trees can be easily identified by their buds. Those on the trembling aspen are dark and shiny while the buds of the large-toothed aspen appear frosted with tiny hairs.

Here you can see the difference in size and leaf edge of the two species.

The geographic range of the trembling aspen is perhaps the greatest of all trees on the North American continent, stretching westward into the mountains and northward practically to the edge of the tree line. There they are capable of enduring intensely cold winters. Large-toothed aspens are incapable of putting up with temperatures lower than 40 degrees below zero Fahrenheit.

One of the most important features of aspens is their role as nurse trees in the natural succession of plants. One can accurately call them pioneer trees as they spring up quickly along shores, in burned-out areas and where the soil has been disturbed and depleted.

They demand open sunlight as they grow very rapidly. Their crowns form an intermingled canopy providing temporary shelter for other trees such as pines. Eventually the aspens, whose lifespan is rarely more than 100 years, give way to the pines, oaks or maples which will predominate in what is referred to as the climax forest.

In examining and marveling at the beauty of some fallen aspen leaves, notice their unusually flat leaf-stems, better known as petioles (PET-e-oles). Hold the very end of one of the petioles and then carefully “wind up” the leaf by turning the leaf blade round and round. Still grasping the petiole, quickly let go of the leaf blade to see it rapidly “unwind.” Naturally it is these flattened leaf petioles that enable the leaves to tremble in the slightest breeze and to carry on that wonderful “whispering conversation.”

One activity we enjoyed doing with students in our nature classes was holding a younger, perhaps four- or five-inch diameter tree trunk, and placing your ear tightly against the tree. The motion of the trembling leaves sounded like a rushing waterfall.

Most of the aspen trees end up in the paper mills, where many people are employed and where a considerable amount of the pulp is transformed into newsprint, magazine and book paper. I look at the number of periodical magazines and books in our own library, then multiply that by millions to represent others like us and flatly admit that the trembling aspen is the most important tree in our lives. Maybe that’s what they’re whispering about!

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