Illustration by Adelaide Tyrol
In late March or the beginning of April, trembling aspen flowers, like those of the familiar pussy willow, are among the early signs of spring. The gray-green catkins open well before the leaves come out, and seed production is finished just four to six weeks later.
Usually called popple in northern New England and quaking aspen in other parts of the country, this tree’s light green leaves ceaselessly rustle, even when the air seems to be still. The leaf stalks are flattened at right angles to the leaf blades, and it takes next to nothing to get the leaves shimmering and whispering to one another.
One closely watched 23-year-old aspen made approximately 1.6 million seeds, seeds so light that 200,000 of them weigh about an ounce. Each tiny seed has long silky hairs that help keep it aloft to be carried, sometimes for miles, on just the faintest breeze.
If the landing pad is acceptably moist, the seed will germinate within a day or two. The hairs both help anchor the seed and absorb water from the soil until the seedling develops an adequate root system.
Yet, in spite of the multi-purpose hairs and the prodigious seed output, most of the aspens you see have not grown from seeds, but have sprouted from their parent’s long lateral cordlike roots to form a genetically identical group or clone. Aspens can keep producing new shoots this way indefinitely, and one clone in Utah – spanning 107 acres – was found to have approximately 47,000 stems.
When the parent tree dies, the hormone that represses the growth of root sprouts, also called ramets, is no longer produced, and the sprouts grow vigorously, helped initially by the food reserves stored in the roots. High soil temperatures also repress this same hormone, which is why aspens can aggressively invade abandoned fields, even when the parent tree is alive and well.
Still, the best way to propagate aspen is not to heat the roots but to cut the large trees down. Aspen is such a choice tree for so many wildlife species that patch cuts or small clearcuts are often recommended when there is an aspen component in a forest. If aspens are left to die of old age, they are likely to be replaced by longer-lived trees that have grown up in aspen shade, producing in turn more shade than the root sprouts can tolerate.
If you cut about a third of your aspen stand every 15 years, you will eventually have trees of many different ages, which will benefit many species of wildlife. Ruffed grouse require aspen in all sizes. They brood their young in sapling stands, overwinter and breed in pole-sized stands, and use older stands for winter food.
Under the right conditions, aspens are fast-growing, heavy feeders, and the roots are well adapted to seek out and extract nutrients as well as to produce offspring. The cordlike roots meander two to four inches below the surface a long way from the trunk without tapering. Sinker roots with a brush of fine feeding roots at the tip drop from the horizontal roots, sometimes to great depths. Seedlings a mere one year old have already developed the capacity to reproduce from root sprouts. As is often the case with those who live in the fast lane, life is relatively short for the aspen. In the East, decline by age 60 is the norm.
As life nears its end, aspen afflictions are numerous and larger trees almost invariably show signs of decay. A stem canker, Hypoxylon mammatum, is probably the most destructive aspen disease in New England. The tunnels of a woodboring beetle, Saperda calcarata, weaken the wood, and the female of this species deposits her eggs in tiny holes drilled into the bark. These seem to be entry points for the Hypoxylon fungus.
Although Vermont and New Hampshire are in the southern part of the range of trembling aspen, the range extends so far to the north and west that it is the most widely distributed tree in North America.
Not only does aspen spring to life early but also it hangs on late, and the leaves, which are a green foil to maples’ reds, turn a clear yellow only after the rest of the forest is in grays and browns. Aspen clones shine like golden islands on the hillsides of late autumn.
Virginia Barlow is the editor of Northern Woodlands magazine in Corinth, VT.