Aspens in Santa Fe National Forest. Sarah Baldwin/For The New Mexican
When we bought our house in Casa Solana 16 years ago, I inherited an expansive yard and someone’s fantasy of a Western garden. Aspens and roses were scattered among boulders surrounding a small pond. It was winter, and I was not yet a gardener.
In the spring, I realized the aspens were largely fried, having been placed against south- and west-facing cinderblock walls, and the plastic-lined pond was leaking into the dry, sandy soil. Other trees and shrubs whose names I did not know were among the casualties of drought. A couple of the aspens, in more protected areas of the yard, survived. I’ve nursed them along over the years; recently one has all but died and the other is afflicted with various ailments. I treasure it and will mourn it when it goes.
But it’s time to rethink our relationship with this beautiful, iconic tree. Ongoing drought and higher temperatures have created new stresses for an already stress-prone species, and even in their native habitats many are suffering.
Let’s start by acknowledging that they are not lone trees that happen to show up in large groups. A stand of aspens represents a single organism, with each tree genetically identical to the others, having sprouted from the same widespread root system. For this reason, an aspen grove is called a clone. The largest clones are wild, ancient, massive beings, whose spindly, short-lived trunks encompass a fraction of their life force, most of which is underground. The oldest known clone, named Pando, spreads across 107 acres in Utah’s Fishlake National Forest and is estimated to have lived for more than 80,000 years. Like many other clones throughout the West, it is now in danger of dying.
Why would this be? Aspens are aggressive pioneers of disturbed sites and are adaptive to diverse conditions. According to the National Forest Foundation, quaking aspen (Populus tremuloides) is the most widespread tree in North America. Usually found at elevations from 5,000 to 12,000 feet on sandy or gravelly slopes, it likes abundant sunshine (even its trunks can photosynthesize) and moisture, though it can survive dryer conditions.
Except for the preference for moisture, you would think these tendencies would make them well suited to our time and place. Yet we have an apt new name for the extremely fast die-off that is happening in various parts of the West: Sudden Aspen Decline, or SAD. Local experts I spoke with say Santa Fe’s aspens have been in decline since the mid-1990s, and especially in the last 15 years.
Aspens are natural hosts to many pests and pathogens, but according to arborist Tracy Neal, the poplar twig gall fly (Hexomyza schineri) population has exploded since the drought of 2000-03. This pest is difficult to control and spreads easily to nearby aspens.
Even those on the campus of St. John’s College, in a higher and cooler setting than much of Santa Fe, have been exhibiting symptoms of black spot (the Marssonina fungus), among other problems. Mysteriously, says Jeff Clark, horticulturist and head of landscaping for the college, lab tests for pathogens have been coming back negative. He said that more water does not make a noticeable difference. The aspens planted in a lawn and getting more irrigation are just as stressed as those in drier locations.
Santa Fe County Extension Agent Tom Dominguez reports he gets repeated calls about ailing aspens and now strongly recommends against planting them in town. He notes that even at higher elevations they are at risk.
Like other experts, Bob Pennington of Agua Fría Nursery believes the underlying culprit is climate change. Santa Fe’s aspens are adapted to a relatively short and predictable growing season. Warmer temperatures have stretched this growing season by many weeks. Additionally, the winter snowpack that keeps them happy and healthy is, if not a thing of the past, at least highly unreliable.
As long as the demand is there, Agua Fría and other nurseries will continue to sell aspens. But in my yard I’ve been planting trees and shrubs acclimated to hotter and drier times. Depending on the location, plausible alternatives include New Mexico olive, Gambel oak, bigtooth maple, serviceberry and curl-leaf mountain mahogany. Talk to staff at local nurseries about what might work best for your situation.
Sarah Baldwin is a freelance editor and writer. She recently completed the Santa Fe Native Plant Project (SNaPP) training offered by the Santa Fe Master Gardener Association.