Outside my windows, an aspen tree seems to be generating its own sunlight filling the room where I stand with a brilliant yellow shimmer. I glance across the valley where a stand of aspen is vibrating with deep orange, gold and scarlet red as if it were on fire. I cannot remember ever experiencing an autumn so breathtakingly beautiful. I proclaim this out loud, and my husband reminds me that I say this every year. But this year is truly the best. I am sure of it.

Feeling incredibly lucky to be alive in Colorado on this October morning, I reach for the newspaper. An article declares "A symbol of the American West, the aspen tree, is dying quickly and mysteriously.

Scientists are scrambling to get to the causes of this epidemic." As a retired environmental scientist and a lifelong naturalist, I have been following these stories for some time. However, in recent weeks there has been much coverage of the aspens plight by local and national media. Perhaps, aware that this iconic fixture of the Colorado landscape may be in trouble, am I more appreciative of the magnificence of Populus tremuloides this fall?

But I have always been an advocate of our native aspen, having risen to its defense many times in horticulture classrooms when instructors - prominent arborists - call it a trash tree and a weed tree not worthy to be a landscape tree! In their defense, in the landscaping world, the aspen is known to be an invasive tree, with a short life span prone to insect infestation and disease. I've protested that its autumn magnificence alone outweighs all of the potential problems. And, moreover, the species has immense value to our native wildlife.

If you, too, are an aspen advocate, please read on.

Some facts about Aspen
The aspen is the most widely distributed tree in North America. It is a member of the willow family. Aspen grow in many soil types and are quick to venture into disturbed sites and unstable habitats such as areas that have been made bare by fire, logging, avalanches or mudslides. Looking up at a mountain slope you can often discern where these events have taken place by looking for the stands of aspen. Driving along I-70 and other roads through Clear Creek County, you can even identify sites of old mines by the small groups of aspen that have taken over the cleared areas near the mineshaft.

Although aspen do reproduce by seed, here in the dry west, most reproduction is done vegetatively by sending out shoots called suckers. Aspens joined by interconnected root systems are called stands or clones. All of the trees within the same stand have identical genetic make up.

Thus, they are considered to be one living organism. Although the life span of the individual aspen tree is relatively short by tree standards, each clone system can live several hundred years. A tree may die, but beneath the soil, the root sends out fresh shoots thus continuing the life of the stand.

Throughout the Rocky Mountains, there are stands of quaking aspens that stretch for miles. One of the largest has been identified in Utah, south of the Wasatch Mountains, Scientists have named it Pando. Pando, a male stand, is often said to be the world's largest living organism. (This may now be in doubt, as genetic analyses of aspen stands are now revealing that trees that were once considered to be part of a single clone system do not have the same genetic make up and therefore must be parts of multiple stands. Or, perhaps these trees are part of the same stand, but, over time, mutations in its genetic makeup have occurred.

Either scenario may be instrumental in finding a way to ensure aspen survival throughout the West. If you think this is as interesting as I do, you will need to read far beyond the boundaries of this article.)

Eventually, many aspen stands are replaced by longer growing species. Conifers gradually invade the stands and begin to shade out young aspen sprouts. Aspen cannot survive in low levels of light. As a participant in the Colorado State Forest Service Forest Stewardship program, my husband and I strive to clear back conifers that are creeping into the aspen stands that dot our forest property.

Aspen as a wildlife habitat
Aspens benefit our native wildlife. Along with many other species of birds, the pine siskin, black-headed grosbeak, yellow rumped warbler, mountain chickadee, northern flicker, hairy and downy woodpecker, ruby-crowned and golden-crowned kinglet, and red naped sapsucker frequent the aspen trees in my garden as well as the "wild aspens" beyond on my property.

Aspen buds and catkins are said to be a preferred food for grouse. Red naped sapsuckers (see photo) forage on healthy aspen trees, unlike most woodpeckers who choose those trees which are diseased or dead. The red naped sapsucker's drilling, identified by its distinct checkerboard pattern, can be extensive, but rarely causes a tree to die. When trees do die, the snags are used for protective cover and the dead trees for nesting cavities.

Aspen is a host plant for the western tiger swallowtail, the red-spotted purple, and Weidemeyer's admiral butterflies. Aspen forests are also excellent habitat for deer and elk who like to browse young aspen and rub their antlers against the trunks, especially in fall and winter. Beaver, pika, black bear, tree squirrels, rabbits, porcupine all partake in dining on Populus tremuloides.

Aspen as a landscape tree
Aspen are commonly available in nurseries and very inexpensive as nursery trees go. Because of their relatively small size, they are perfect as a foundation plant serving to bring the autumn glory "up close and personal". They also provide a wonderful backdrop when planted on the outskirts of your garden.

Aspen do so well here in our Zone 3-5 gardens at elevations between 7,000 to 10,000'. After all, they are our local native deciduous tree so they must like living here! They can be planted in either fall or spring. I've planted all of mine in October or early November and they have survived just fine. Remember that they require fall and winter especially during the first years after planting. Common insects and diseases include aphids, ink spot disease, aspen leaf minors, Marssonina blight and trunk rot. However, some of these diseases occur only when planted at lower elevations, most are not fatal and some do not even impact the health of the tree. Aphids and trunk rot actually are beneficial to the birds that frequent your garden, either as food or for nesting. (Look on the bright side!) As with any other tree, you need to learn how to prevent and how to recognize and treat problems if they occur.

The reason aspens are able to take over a disturbed area in the wild is that they are, by nature, invasive. In your garden or landscape, their powerful root systems will push up suckers throughout your garden and lawn. As a frugal, but patient, gardener, I rejoice in the fact that having planted several aspen five years ago, I may never have to buy or plant another. Some the oldest suckers are now over ten feet in height and ready to face life unprotected by the elk and deer cages they have outgrown. However, I do have to deal with the suckers that sprout up prolifically where they will not survive or where I do not want them to survive. Since using a weed killer will harm the mother plant and is against my gardening ethics, I remove unwanted sprouts by inserting a shovel into the ground and severing the root connecting the sucker to the mother tree. You can also mow any suckers that sprout in your lawn.

Providing good habitat for elk and deer in the wild is one thing, but setting out an all-you-can-eat aspen buffet in your garden is another. Therefore, protect your young aspens from unwanted garden visitors as you would any young tree or shrub. Also, surround the trunks of older trees with chicken wire or heavy plastic mesh at browse height. Keep in mind what creature you are trying to deter. Protect the lower portions of the trunk from gnawing by small mammals. Along creeks and streams, you may also need to protect all of your aspens from beaver.

The future of Aspen
The plight of aspen is cause of current concern especially in Utah, Arizona, Colorado and parts of Canada. A conservative estimate is that ten percent of the aspens in Colorado have died or have become afflicted in the past decade -- slightly less than 600 square miles of dead or dying trees. Although disease in aspens have been observed in the past, it is only in recent years, that massive die offs have been observed. Scientists speculate that drought, disease, global warming, insects or a combination of these factors may be the cause. This widespread root death could mean that the aspen will not come back in the affected areas. As biologists and forestry experts gather to determine why there has been such a rapid die off, some of the research and remedies being presented does give reason for hope.

As a an environmentalist, a naturalist, a gardener and as an ardent "leaf peeper," I will cling to that hope as I watch the last golden leaves fall from the trees in these final days of autumn glory. This autumn the aspen put on the best show ever and next year will be even better.

Nan Spence is president of the Evergreen Garden Club. Please visit the club's website at www.evergreengardenclub.org for more gardening information.