When we think of the sounds of nature like the spine-shivering call of a Canadian loon the idea of the natural noise of plants is not on the radar. Yet plant sounds are part of the fabric of our living landscapes. Imagine the whistling moan of the west coast wind passing through the sky-high branches of Sitka spruces (Picea sitchensis). Perhaps our most conversant and widely-heard plant is the trembling aspen- a plant whose calming rustle is a consequence of its very botanical structure.
Trembling aspens are the arboreal icons of the interior British Columbia landscape. Growing as colony-forming trees they reach from head-high dwarfs to 25 m tall giants. The colonies are clones of a single genetic type, consisting of root sucker shoots of the same plant, connected underground. Some people have suggested that these aspen stands represent the largest individual organisms on earth. Trunks and branches are creamy to greenish white often covered in a thin greyish dust. Ancient trunks turn dark, corky and fissured. The simple deciduous leaves are arranged alternately. They are pointed, broadly egg-shaped to somewhat circular, tending toward a heart-shaped base. Size ranges from about 3-9 cm long by 3-8 cm wide. Leaf margins bear long white hairs and small teeth. The upper leaf surface is medium green, however underneath it is noticeably paler. In the cooling days of fall the leaves turn brilliant gold and light up the mountain sides and valleys, providing a last cheerful burst of colour before the cold frozen winter.
Trembling aspen’s talkative tendency derives from the leafstalks. They range from 2-7.5 cm long and are distinctively flattened. The flattened form allows them to dance or tremble in the wind. Indeed Salish elders of south Vancouver Island called it the dancing plant or tree. Even with the faintest breeze the leaves rustle, and they literally snap at higher wind speeds.
Aspen flowers appear in mid-spring with males and females on separate plants. The male catkins reach 2-3 cm long, the females 4-10 cm long. Each ephemeral male flower is packed with little stamens. The female flowers mature into short-stalked, lance-shaped capsules with fluffy seeds that drift widely upon warming spring and summer winds.
Trembling aspens inhabit many sites from ravines, meadows and swales to forests, upland slopes and ridges. They form distinctive groves or copses in otherwise open terrain. They occur from lowland valley bottoms far up mountain slopes. Widespread from Alaska to Arizona, they nearly dominate the lowland interior landscape of British Columbia. Though absent from most of the coastal zone, a distinctive variety occurs on eastern Vancouver Island and Gulf Islands. Now uncommon, it may have dominated the landscape 12,000 years ago, when now-extinct giant bison roamed widely.
First Nations knew the trees well and had many uses for them. Coast Salish people used it as an important general internal medicine. For this purpose an infusion of the bark was made by pouring hot water on it and then drunk. Mixed with other tree barks it was also a constituent of another powerful medicine and some even recalled it being used for birth control. In the interior, the Ulkatcho People of the west Chilcotin knew trembling aspen as a strong medicine and the bitter bark could be boiled or chewed. Aspen bark like willow bark contains salicylates, the same medically active compounds in willows and the original basis for aspirin (acetosalicylic acid). Externally, medicinal preparations were used for earaches and insect bites. The sweet spring inner bark was eaten, but turned bitter as the weather warmed. The light wood was fashioned into tipi poles, canoe paddles and bowls. Lye made from aspen ashes and animal fat was turned into soap and used to prepare moose hides.
These remarkable trees grow so widely that it is hard to imagine the need to conserve or even plant them. Aspens have enormous ecological values including wildlife benefits such as beaver food, habitat for many animals and the capacity to stabilize soils and generate masses of organic matter. They are widely used in restoration, being best propagated from seed but also from cuttings. Aspen-dominated watersheds produce water of high quality.
Certainly the coastal copses deserve conservation and protection. They are not the same as the widespread inland variety. Many have been destroyed or badly reduced because they occur in now-urbanized zones of Victoria and surrounding communities. Even inland patches provide unusual habitats and the trees themselves are especially important for cavity nesting birds such as woodpeckers because of the easily excavated soft wood.
Next time you see aspens do not dismiss them as some sort of woody weed. Rather think of them as habitat, as remarkable well-adapted natives with an ancient history in BC. Think of them as brilliant golden symbols of the fall and the coming respite of winter. And imagine how silent it might be without the gentle calming rustle of their dancing leaves.