By Craig & Liz Larcom
Come fall, quaking aspen wouldn't be more conspicuous if it were a kid hollering, "Mom, Dad! Look at me!"
Robed in dazzling yellow, these familiar trees of the foothills and mountains are particularly eye-catching this time of year. Known also as trembling aspen, this tree is the most widespread in North America. Yet in the East the aspen tends to blend in with other hardwoods, so much that some folks don't even know it's there. But in the West, where it stands out among the conifers, residents know and cherish it.
Much of its appeal is linked to its unique "quaking." With leaves that dangle from the end of a long, flattened stalk, the aspen's foliage dances in the merest puff of air. The leaves shimmer and murmur whenever a gentle wind passes through. Aspen leaves whisper and rustle, making a lighter sound than the cottonwood's heavier leaves.
In summer the tops of aspen leaves are shiny green; the undersides of the leaves are much paler-perfect for projecting a glittering effect that is all but impossible to ignore. In autumn, the shimmer turns to gold.
Certainly a large part of its magnetism comes from the fact aspen are brushed in the brightest color in the autumn paint box. Placement, too, gives aspen an edge over other trees. Often found in clumps at the edge of a meadow, aspens provide a welcome retreat for hikers looking to picnic out of an Indian summer's sun. The clumping is due to the fact that here in the West, almost all quaking aspen are clones. They change color in lockstep because entire groups are something like identical twins.
In fact, autumn can be one of the best times of year to see whether a stand of trees is a single clone or more than one-just observe how many patches of color make up the group. Whether the group is in different stages of change from green to yellow, or orange and red, differing bunches of color translate to different DNA. If it's a small stand, then it's usually a single clone. Larger stands, however, may be made up of several clones, which will vary not only in color, but also in subtle features like bark whiteness, leaf shape, growth rate, and likelihood of disease. Clones in other states have been known to include as many as 47,000 trees. These have interconnecting root systems, so in a sense, the largest living organism on the planet may be a quaking aspen clone!
But how does an aspen make clones? Loitering on a shallow root, as many as 600 "sucker" buds will crowd into a given 18-inch length, waiting for the moment to sprout. Spring will prompt a few to grow. But let a fire or other source damage the tree's crown and suckers will sprout by the dozens from each aspen. In the first year after a fire suckers sometimes grow four feet. That phenomenon gives aspens a considerable head start on the competition that starts from seed, which some aspen do as well.
In fact, a female tree may produce a million tiny, cottony seeds. In spring these drift on the wind, much like those of their relatives, the cottonwoods. Rarely, though, will they become trees. Aspens seedlings in the West must find a good combination of bare soil, plenty of sunshine and an even supply of moisture to survive. Still, occasionally the conditions will come together in the perfect season, allowing an aspen to start. Once it does, its roots and the additional trees that grow from it may live for 80 to 100 years. That's a short life as far as trees go. But the cycle can continue if a renewing fire damages the older aspen stand and prompts a host of trees to sprout anew from the senior root system. If there is not a fire, new trees probably won't grow because seedlings need plenty of light to thrive. Conifer seedlings, on the other hand, need shade to develop. Thus, aspen stands make the ideal nursery for these evergreens that will eventually surpass the aspen and shade them out.
Until then, fall hikers and other late-season recreationists can enjoy a picnic under these extraordinary trees that shimmer in autumn gold.