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Washington State University’s ‘Dr. Christmas Tree’ leads research into trees resistant to climate change

Plant pathologist has noticed 'increased mortality in new Christmas tree planting associated with (the Pacific Northwest’s) hot, dry summers'

By Nathan Gilles, Columbia Insight
Published: December 15, 2023, 3:08pm
4 Photos
Amanita muscaria mushroom grows at the base of a Christmas tree in Puyallup.
Amanita muscaria mushroom grows at the base of a Christmas tree in Puyallup. (Photos by Nathan Gilles/Columbia Insight) Photo Gallery

Washington State University’s Gary Chastagner inspects the tightly packed rows of fir trees that make up his experimental Christmas tree grove.

The moist, dark floor of the grove is covered in red-capped, white-speckled Amanita muscaria mushrooms. The mushrooms surround the firs like so many brightly colored Christmas presents. In fact, these “magic mushrooms” have been heavily implicated in Christmas myths and imagery.

As legend has it, the shamans of the north used to sacramentally ingest the fungi, whose psychoactive compounds are said to have allowed them to fly to the North Star, a yarn that fittingly involves reindeer. This, not Coca-Cola or St. Nicholas, is the origin of Santa Claus, according to some.

All of this is a reminder that Chastagner’s research is blessed with both Christmas and natural magic.

A plant pathologist, Chastagner, aka “Dr. Christmas Tree,” has spent over four decades dispensing the gift of science to Christmas tree growers in Washington and Oregon, using carefully designed experiments to ward off various attacks from Mother Nature.

However, in recent years, Chastagner’s research has converged on a single nagging problem: how to grow a Christmas tree that’s resilient to climate change.

“Over the last decade but in particular over the last five years, we have seen increased mortality in new Christmas tree planting associated with (the Pacific Northwest’s) hot, dry summers,” Chastagner says.

Large numbers of Christmas trees are also believed to have succumbed to direct heat damage during the 2021 heat dome, though exact numbers aren’t available.

But climate change in the Pacific Northwest isn’t just about hot, dry summers and scorching sun.

Chastagner’s research suggests that intense fall, winter and spring rains coupled with warmer soil temperatures creates opportunities for fungi and related pests far less enchanting and significantly more harmful to the region’s Christmas trees than the festive mushrooms in his grove.

This work on climate will be his final gift to Christmas tree growers. Now 75, Chastagner is set to retire next year.

Like a paper chain jumbled at the bottom of a stored holiday box, the compound climate threats facing Christmas tree growers in the Pacific Northwest are obviously linked and frustratingly difficult to unravel.

Wrapped up in the jumble is Chastagner’s biography as a scientist.

Need for new tree species

On a frosty November day, I meet up with Chastagner for a tour of his indoor and outdoor laboratories on the WSU Research and Extension Center in Puyallup.

He is a tall, huskily built man who is clean-shaven and wears bifocals. The top of his head is bald.

He is quick with a smile and a full-bodied laugh. It’s the context of our interview — I know — but I can’t help but think that with a beard and the right red outfit he’d make a top-notch Santa Claus.

His amiable nature has helped make Chastagner a beloved figure among Christmas tree growers.

But what has really endeared him is his science. He knows Christmas trees — what makes them thrive and what makes them die.

From talking with Chastagner, it’s clear. Although Christmas trees might look the same when festooned with ornaments and lights, no two species — indeed, no two individual trees — are genetically identical.

Consider the highly prized North American Christmas tree species: noble fir. While native to the Pacific Northwest, noble fir is a mid-elevation species that tends to grow above 2,500 feet.

The noble firs Chastagner shows me on my tour of his outdoor labs buck that trend, having been selected for their ability to grow well at lower elevations.

“The reason that people can now consistently grow high-quality noble fir is because of genetic trials,” Chastagner says.

Other tree species on the campus include Fraser fir, an eastern North American tree that does best in the Pacific Northwest when irrigated during the dry summer months.

Still more species are even more exotic.

Since the mid-1990s, Chastagner has been experimenting with Nordmann fir. The tree is native to the Caucasus Mountains in Turkey, Georgia and Russia.

He’s also investigating the related Eurasian species Turkish fir and Trojan fir.

The Nordmann, Turkish and Trojan firs that Chastagner shows me come from trips abroad to collect seeds and study genetic traits.

Chal Landgren, professor emeritus for Oregon State University Extension and a longtime collaborator with Chastagner, accompanied him on a seed-collecting trip to Turkey.

“Gary (Chastagner) is a consummate researcher,” Landgren says.

The Turkey trip involved collecting cones from “mother trees” that were then GPS-tagged so future research efforts could find them among the jumble of the forest. The seeds were then shipped back to the Pacific Northwest, where they were planted.

Over the next 10 years, the trees grown from these seeds were tested by Chastagner and colleagues. Branches of top-performing trees were then cut and grafted onto trees in seed orchards around the country, including at an orchard run by Landgren in the Willamette Valley.

“Gary has tested those trees, and only the trees that have the best ‘keepability’ are the ones that are to be put into our seed orchards,” Landgren says. (“Keepability” is industry jargon denoting a tree’s ability to stay hydrated and retain its needles following harvest.)

This work is part of the Collaborative Fir Germplasm Evaluation Project (aka the CoFirGE Project), an ongoing effort involving scientists in Washington, Oregon, North Carolina, Michigan and elsewhere to locate Christmas trees capable of withstanding future climate change.

The conclusion reached by CoFirGE Project participants: Nordmann, Turkish and Trojan fir could have the climate resilience that growers in the Pacific Northwest have been looking for. Research suggests the trees are highly resistant to heat and drought.

“The Turkish, Trojan and Nordmann (firs) we have been working with tend to handle the summer heat we’ve been having in Oregon and Washington better than some of our native species,” Landgren says.

From diseased trees to climate change

The path that led Chastagner to the CoFirGE Project began in 1978.

Chastagner had recently graduated from the University of California Davis and quickly landed a job at WSU, where he would stay for the next 46 years.

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His first research subjects were turf grass and ornamental bulbs — tulips, daffodils and lilies. Christmas trees would enter his life the following year.

In the mid-1970s and early 1980s, Christmas tree growers in Washington and Oregon were dealing with an ongoing epidemic of Swiss needle cast on their Douglas fir trees, then the mostly commonly grown Christmas tree in the two states.

Swiss needle cast is caused by a fungus that attacks conifer needles, causing the trees to dry and prematurely shed, or “cast” off, their needles.

Fed up with the fungus, in 1979 Christmas tree growers in Washington asked for help.

Washington lawmakers responded by mandating WSU to investigate. Chastagner — being, in his words, “the new kid on the block” — was assigned the task.

Chastagner determined that the pathogenic fungus that caused Swiss needle cast was present in 84 percent of the Christmas trees in Washington and Oregon. And although only about 16 percent of the trees had infections severe enough to make them unsellable, this was still 600,000 unsellable trees, amounting to $3.4 million in lost sales.

After determining the extent of the outbreak, Chastagner went on to tackle the disease.

“In managing diseases, it is so important to know the disease cycle and when infection is taking place. And there really wasn’t much information known on when (Swiss needle cast) infection took place,” Chastagner says.

In a series of follow-up studies, Chastagner would describe the disease cycle of Nothophaeocryptopus gaeumannii, the fungus behind the disease.

Knowing the cycle allowed Chastagner to demonstrate that farmers could control the disease by applying a common fungicide at the right time in the cycle. This meant farmers could use far less fungicide than had been previously estimated.

Chastagner’s recommendations were later widely adopted, and Swiss needle cast became a manageable illness rather than an outbreak.

But Chastagner wasn’t entirely convinced that the remaining 84 percent of asymptomatic Douglas firs would remain asymptomatic when subjected to the stress of being shipped and displayed in people’s homes.

Chastagner’s suspicions led to a 1984 study in which he showed that the infected Douglas firs dried out twice as fast and lost more needles than uninfected trees.

This was the beginning of his search for a climate-resilient Christmas tree, work he carries on in his “dungeon.”

Dr. Christmas Tree’s workshop

Chastagner’s “dungeon” lab looks like a cross between a bomb shelter and a clandestine grow house. The building is old, somewhat derelict in appearance and partially embedded in a hillside. It is, in fact, an old cistern.

As Chastagner’s research ambitions expanded, so did his need for lab space. Forced to make do on a slim budget, he helped renovate the building himself, a process that involved excavating a spot for a door, the opening for which was cut through one of the thick, rebar-reinforced concrete walls.

Inside the climate-controlled dungeon, bathed in the preternatural hues of artificial grow lights, it’s a pleasant 68 degrees. Always frugal, Chastagner got his first set of dungeon lights cheap, via a police donation following a drug bust in the Seattle area.

The lights reveal row after row of white tables on which sit vial after vial of tiny Trojan and Turkish fir branch cuttings. The cuttings look identical, but looks can be deceiving.

Chastagner grabs one of the cuttings and, in a swiping motion, proceeds to gently brush off its needles. The cutting is dry as a bone, and the needles flake off easily, falling to the table below.

“Obviously, this one is not a keeper,” he says.

The tree cuttings have been intentionally deprived of water for three weeks. It’s a stress test.

Chastagner then grabs another fir cutting and tries to remove its needles. While some fall off, most don’t.

“Those needles are still very pliable. That’s three weeks as a branch with excellent needle retention,” he says.

Each cutting came from a single tree.

This simple test is designed to identify which tree species and which individuals within those species will retain their needles the longest after being cut.

New cuttings from resilient trees will then be made and shipped to seed orchards where they will be grafted onto rootstock, ensuring the trees’ genes can be used again and again.

Chastagner began doing exactly these kinds of stress tests decades earlier as a way to ensure a better product for consumers. The idea was to test how long cut and displayed trees could retain their needles without having access to water.

But while doing this research, Chastagner had an insight: Because moisture is an important climate factor that determines where plants can grow, he reasoned that what he was really studying was climate stress.

His research with the CoFirGE Project takes both climate and display stress into account.

But the search for a climate-resilient Christmas tree goes beyond this. That’s because climate change isn’t just about hot and dry conditions; it can also be about conditions that are too wet and warm, conditions that lead to another threat to Christmas trees: diseases.

Emerging fungal threat?

In an article published this fall in the Christmas Tree Lookout, the trade magazine of the Pacific Northwest Christmas Tree Association, Chastagner describes the “unprecedented levels of mortality” observed last year in noble and Fraser fir trees.

Chastagner believes the die-off is due to the double whammy of climate — namely wet and warm conditions — and a group of fungal-like pathogens called Phytophthora, water molds that cause “root rot” on firs.

“We saw thousands of trees being killed by Phytophthora root rot by the end of the summer of 2022,” Chastagner says. “And in some cases, it wasn’t heat stress that was killing the trees; it was all that moisture.”

Chastagner says “more aggressive warm-weather” species of Phytophthora could become more common due to climate change. This includes Phytophthora cinnamomi, a species that is currently rare in the region, though Chastagner has found it on Christmas trees in Oregon.

Last year, Chastagner also recorded an outbreak in Fraser fir likely caused by Armillaria, a fungal pathogen that preys on trees weakened by drought.

Chastagner says the continued impact of drought-weakened trees and aggressive warm-weather fungi could limit where Fraser and noble firs can be grown in the future.

Here’s where Nordmann and Turkish fir might also be the Christmas trees for climate change.

According to testing done by Chastagner and others, the Eurasian trees appear to be resistant to the common species of Phytophthora and Armillaria found in the Pacific Northwest.

The jury is still out on Trojan fir, though the species’ fungus and mold resistance is something Chastagner is currently investigating.

Chastagner’s legacy

But with Chastagner’s retirement looming, his part in the story could be ending … maybe.

“We won the lottery when we got Gary interested in our industry,” Christmas tree grower Betty Malone says.

Malone has spent the last 50 years growing Christmas trees north of Corvallis, Ore. She’s known Chastagner for nearly as long and has worked with him on multiple projects.

She’s also unafraid to use the words “climate change,” which she sees as just another reality of being a tree farmer. She credits Chastagner with helping her understand its impacts on her industry.

“He is one of the most careful, thought-provoking persons. Gary retiring is just a huge loss,” Malone says.

Kristi Scholz-O’Leary also knows the climate threats facing the Christmas tree industry. Once a full-time lawyer, Scholz-O’Leary now runs Snowshoe Evergreen Inc., her family’s Christmas tree farm in Washington.

Her family’s trees have seen drought and disease outbreaks, and been helped along the way by Chastagner, whom she considers a friend of the family.

“What I say to everyone about Gary is he is a master collaborator. He is the person who brings everyone together to the table for the benefit of the industries he does research for,” Scholz-O’Leary says.

To ensure that Chastagner’s work continues, Scholz-O’Leary is leading an effort by the Pacific Northwest Christmas Tree Association and Washington State Nursery & Landscape Association to create the Dr. Gary Chastagner Endowed Chair position at Washington State University.

So far, the endowment has raised $250,000 of the total $1.5 million expected to fund the position, according to Scholz-O’Leary.

She says climate change poses a threat to the Pacific Northwest Christmas tree industry, but it’s not one that tree farmers can’t handle with a little help from science.

“I don’t see (climate change) holding anyone back, because if anything, farmers are resilient. We dance with Mother Nature all the time. But you’re going to have to have the science partnered with the grower and the farmer to do that work,” Scholz-O’Leary says.

Not everyone is convinced that Chastagner will actually retire.

“I don’t know that Gary will ever totally retire. He’s a workaholic,” Oregon State University’s Landgren says. “With Gary, I will believe he’s retired when he signs on the dotted line.”

Landgren might be correct. As Chastagner is wrapping up our tour, he tells me of a new research effort to test what is, in effect, sunblock for trees to help them avoid direct sun damage like what occurred during the 2021 heat dome.

But the last thing he says really gets my attention.

It’s just before Thanksgiving. Chastagner says he plans to spend the long holiday weekend in Arizona with his family, or at least most of it. He does plan to sneak off for a bit, infrared sensor in hand, to measure heat stress in Christmas trees.

“My family expects me to be gone part of the time after Thanksgiving, because I’m going to go around and look at Christmas tree lots,” Chastagner says.

Columbia Insight, based in Hood River, Ore., is nonprofit news site focused on environmental issues of the Pacific Northwest.