The Christmas tree doctor is in.

When Gary Chastagner was a kid in the 1950s, his parents typically displayed their Christmas tree for about a week. The tree went up on December 24—often after he went to bed—and came down after New Year’s Day.

Now, consumers want fresh-cut trees that can be displayed for weeks without losing their needles. Chastagner, a professor emeritus of plant pathology at Washington State University, has spent more than 40 years helping Northwest Christmas tree growers improve their product. For his work, Chastagner earned the nickname “Dr. Christmas Tree.” 

In this episode, Chastagner talks about working on solutions to Swiss needle cast disease in Douglas fir and visiting tree lots in the Southwest to improve the hydration of displayed trees. He’s also visited other countries to scout out new Christmas tree varieties. 

Chastagner was honored with a lifetime achievement award from the National Christmas Tree Association in 2018.

He retired in April 2025 from the WSU Research and Extension Center in Puyallup, where he also worked on ornamental flower bulb, cut flower, and nursery stock research. 

The Dr. Gary Chastagner Endowed Chair in Plant Pathology has been created and is raising money to continue research with the Christmas tree and horticultural industries. 

Read more

Northwest growers test new tree varieties as droughts threaten Christmas crop (NWPB, Dec. 2, 2025)

Oh, Christmas trees! (Washington State Magazine, Winter 2022)

Talkin’ around the Christmas tree: Stories, history and tips (Washington State Magazine, Winter 2022)

Ask Mr. Christmas Tree (Washington State Magazine, Winter 2013)

Transcript

Washington State Magazine webisodes

Episode 43: The Christmas tree doctor is in.

Larry Clark:

Picking the right tree for Christmas is an art, but it's made easier thanks to decades of work by one man. Gary Chastagner is widely known as Doctor Christmas Tree. For more than forty years, the Washington State University professor emeritus has helped Northwest Christmas tree growers improve their product. [music] Welcome to the Washington State Magazine podcast. We bring you WSU stories from all corners of Washington and beyond. I'm Larry Clark, editor of the magazine. Oregon and Washington are large producers of fresh cut Christmas trees. A plant pathologist, Chastagner has worked on issues related to disease, needle loss and genetics, and Christmas tree varieties. He also contributed knowledge about how fresh cut Christmas trees can be displayed indoors for weeks, retaining their beauty and their needles. In this episode, Chastagner talks with Washington State Magazine science writer Becky Kramer about working on solutions to tree disease, visiting tree lots in the southwest to improve hydration of displayed trees, scouting new Christmas tree varieties around the world, and his own Christmas tree traditions. [music]

Becky Kramer:

Gary, welcome to the Washington State Magazine podcast. 

Gary Chastagner: 

Oh, thank you very much, Becky. 

Becky Kramer:

So you've spent more than forty years working with the Christmas tree industry. What issues were northwest growers facing when you started this work? 

Gary Chastagner:

Well, I'd just been hired in nineteen seventy eight. I wasn't hired to work on Christmas trees. I was hired to work on ornamental bulb crops and turfgrass. But the Christmas tree industry in the Pacific Northwest, which is the largest producer of Christmas trees in the United States, they were having issues with a disease called Swiss needle cast. This is caused by a fungus This fungal pathogen and it attacks Douglas fir and Douglas fir was the most common species that the growers were using, and it caused a premature casting of needles. They would go to harvest trees, and if they had a lot of Swiss needle cast, there'd be very few needles, except for the current season of needles on the trees. So the legislature basically requested that WSU assign someone to help the industry work on this problem. I was sort of the new kid on the block, was working on ornamentals, and so I was requested to start working on this. WSU contributed thirty thousand dollars to start the Christmas Tree Research program in nineteen seventy nine. 

Becky Kramer:

You've mentioned in the nineteen fifties that people kept their Christmas trees for about a week. How has the expected shelf life of fresh cut trees changed over time? 

Gary Chastagner:

It's changed tremendously. So when I was a young kid in the early fifties, I can vividly remember going to bed on Christmas Eve. No Christmas tree set up yet, no presents, and then waking up in the morning. And my mom and dad had set up a Christmas tree, decorated it with presents underneath and stuff. So we generally displayed trees for about a week from Christmas to New Year's. And I think that was the case in many situations. The trees were set up closer to Christmas and generally taken down right after New Year's. Now there are people who are opening their retail lots, choosing cut farms the weekend before Thanksgiving. Traditionally, it's always been the weekend after Thanksgiving. The pressure now is that there's a lot of people who are looking for trees before Thanksgiving. So that creates a tremendous challenge to have a tree that will last that long if you bring it in and display it immediately when you buy it. You're asking a tree to to last for four to six weeks, which many species will not do even if they're properly cared for. 

So there's been a big change. You see a change in an increased utilization of species like noble fir, Fraser fir and other areas that have much better post-harvest capability, moisture retention, needle retention characteristics than some of the species that used to be grown. 

Becky Kramer:

So that four to six week display time. Is that a realistic expectation? 

Gary Chastagner:

Yes, we we have some very unique facilities here that have allowed us over the years to do post-harvest trials. The first post-harvest trial we did was with Swiss needle cast infected trees. We were able to solve that problem for the industry by them making one or two applications of a fungicide two to three years. So there were many trees that were being grown at that time that were not severely impacted, but they had needles that were colonized by this pathogen that causes Swiss needle cast. I wanted to know what effect the presence of those infected needles had on the postharvest quality of those Douglas fir trees. So we did a series of trials and showed that if you had Douglas fir that had Swiss needle cast needles, those trees dried out twice as fast. So the control not only eliminated the loss at the time of harvest from trees that wouldn't make grade, but it also improved the postharvest quality.

 So if you look at Douglas fir, which is a very common species still grown in the Pacific Northwest. If you display it in water, you can expect those trees to last about three to four weeks. If you take a noble fir and display it under the same conditions, making sure that it's displayed continually in water, doing all the things that are recommended, that tree can easily last six to eight weeks. And so potentially, if the tree is properly cared for when it's set up and displayed, you can expect them to last for a very long period of time. 

Becky Kramer:

You've taken some road trips to lots where people are selling fresh cut trees. Tell me about some of those trips and what you were looking for and and what you found. 

Gary Chastagner:

Sure. The Pacific Northwest, as I indicated, is the number one producer of Christmas trees in the United States, but these trees are shipped throughout the United States. The major markets for northwest trees are usually are down into California, particularly Southern California, Arizona, Texas areas like this. So there were always questions about, well, what's the moisture status on these trees? Are they being harvested too early? The growers start harvesting them in maybe early November, store them for a period of time as they're working to build up inventory, and then they're shipping them to these markets. 

Part of our post-harvest work with Swiss Needle Cast, we had shipped a set of trees to California, to UC Davis, where I graduated from, and I had a collaborator down there who set trees up. Well, we also set some of the same trees harvested from the same fields up in Puyallup here at the research center. And there were two trees that were shipped to Davis. They lost a significant amount of green needles shortly after being set up. Well, this is a common concern of consumers about messiness and loss of needles. So when we went back and checked what was different about those trees, those trees had dried more than any of the other trees by the time they had set up. 

So that led us to ask the question, how far can we dry down a tree? Is there a critical moisture level that you can dry it to that shifts it from not shedding to shedding? And with Douglas fir, it was it would be drying it down to a moisture level. We measure this with a pressure chamber what's known as in bars. So minus thirty five bars a fresh tree would have a moisture level of water potential level of about minus five to minus ten bars. So what happened is we did a lot of research to look at how far you could drive trees down after harvest. What effects storage had. And under our cool, moist conditions that we have in the Pacific Northwest, most of the drying is not occurring during after harvest and storage in the Pacific Northwest. It's too cool. It's too moist. Where we do see drying is when they're on the retail lots, particularly in warm weather markets. So that led us to understand that Douglas-fir had a threshold water potential of about minus thirty five bars. If you harvested that tree and didn't allow it to dry below that, you could recut that base. 

And these trees are phenomenal. They'll rehydrate back up to the moisture level of a fresh cut tree. 

So I did my first retail lot surveys all the way from Washington, Oregon, down into Southern California, You just visiting retail? Lots. I took a pressure chamber with me and we're measuring water potentials on these. And at the time most trees on retail lots were displayed in wooden stands. They were not taken care of like they are today. There are very few trees that are dried below the threshold moisture in Washington. But when we got to Southern California, about sixty percent of the trees on the retail lots had dried below the threshold moisture content, indicating that those consumers, if they purchased those trees from those lots, they were likely to have trees that would not either rehydrate very well or might show needle loss problems. 

So subsequent to that, we've done a lot of retail sampling. Arizona, Texas, Boston, Wisconsin, Chicago area, Michigan, Florida. I've even gone to Alaska looking at the moisture status of trees. And because I got these comments all the time, well, you're sampling into the these warm weather markets. We don't have this problem in the Northeast in Boston. We don't have this problem in Michigan. Well, it turns out they do. They have cold conditions, which are also very dry, and the trees can desiccate. 

So we've done a lot of work as it relates to understanding where moisture stress is coming in. And largely it's related to how the trees are handled and cared for in these market conditions. So that's led to some changes then in terms of how retailers display trees. Oh, very much so. We actually set up a retail lot. An experimental retail lot at Arizona State University on their campus, had access to a facility there where we shipped trees. We set trees up and looked at the standard practice of just displaying them without being in a water stand, displaying them in a water stand, or like if you think about your vegetables, if you go in the produce section in a grocery store. Now there's a micro mister there that comes on. So we even had those set up where we would micro mist the trees going into the evening. That would result in free moisture on them all through the evening and into the morning. Of course, if you displayed the trees in water, they did fine. They had excellent moisture retention. If you displayed them in water and micro, they were even better. But if you just micro mist the trees without displaying them in water, you also had trees that did not drop below these thresholds. That resulted in a significant change in how retailers display their trees. 

And we've done a lot of training with industry groups on how to properly care for trees and ways to improve the quality of the trees that they're selling. 

Becky Kramer:

I was also curious how you got the nickname Doctor Christmas Tree. 

Gary Chastagner:

[laughs] Well, I don't know exactly, but there's a lot of media attention about Christmas trees during the Christmas season, we would always have media people coming and wanting to know what was going on. We've had television crews, radio, TV crews, print crews here doing all kinds of things over the years. One of the reporters, I think it was probably one of the Seattle newspapers at the time, wrote an article and referred to me as Doctor Christmas Tree. 

I remember another reporter from the Seattle Times. They did a big story here, and the reporter called me up the day the story was coming out, and it was a front page story. And she says, Gary, I hope you're not going to be offended by the story because I refer to you as a scientific Santa Claus. [laughs]

So it's really interesting and interacting with the reporters, and they're looking for ways to make people want to read their stories and stuff. So that title is sort of stuck. And a lot of people refer to me as Doctor Christmas Tree. 

Becky Kramer:

It's definitely a tagline that you're known by. So you have a test site at the Puyallup Research and Extension Center, where researchers look at different Christmas tree varieties from other parts of the world. Have you had any success with some of those other varieties? 

Gary Chastagner:

Yeah, one of the things we're very fortunate here at Puyallup is that we have facilities that we've developed over the years to do post-harvest work, but we also have a land base here that allows us to plant trees fairly close to the center. I've been very fortunate in my career to be able to travel and visit a lot of research people, and I would say that when people come and visit here, they're amazed that I can go from my office, walk across the street, out into one of the fields, and there's five acres, ten acres of Christmas trees, experimental Christmas trees, because we have that land base and it's close by, which allows us to take a lot more detailed data because we're not having to travel three hours, four hours or whatever. And so we can collect data. 

Currently, we're evaluating a number of Eurasian species of true Firs. And by Eurasian I'm talking about countries around the Black Sea, the Caucasus Mountains and the Republic of Georgia going down into Turkey. And some of these. The reason we got interested in them is because they had fairly good tolerance to Phytophthora root rot, which can limit where growers can produce noble fir, which is probably sort of a Cadillac or one of the premium types of Christmas trees. But if you have soils that have poor drainage, high moisture levels, Phytophthora is favored by those conditions. And noble fir, even Fraser fir back in North Carolina and elsewhere, are very susceptible to that disease. Well, we were working on trying to identify species that were more resistant or tolerant. And we found that some of the Eurasian species were quite tolerant to that disease. 

We've had some projects in Denmark where Nordmann fir is the principal species grown as a Christmas tree. And then have done some collecting trips in Turkey and in the Republic of Georgia to identify and collect sources of these species, and have then brought them back, grown them as seedlings. These are collaborative efforts that involve multiple institutions. It only happens because we have these collaborations, but then we put these plantings out in different locations throughout. In the case of the US, throughout major Christmas tree production regions, and then evaluate them over the seven or eight or nine years that it takes to grow that as a tree. We do disease susceptibility work, and then we do post-harvest work on all those trees and identify individual trees or individual sources of trees that have really desirable growth characteristics, foliage quality characteristics, and post-harvest needle retention and moisture retention characteristics. Those individual trees are then grafted into seed orchards, and are being used to produce seed that is coming from other trees that have these desirable characteristics. And the work we did in Denmark showed that the progeny from mother trees that have those desirable characteristics. 

So we have a number of these trials. I just got back a week and a half ago from evaluating the planting down in California in the Placerville area, which is in the Sierra Nevada between Lake Tahoe and and Sacramento. We have a planting in Idaho, and we have a planting here, and there's a planting in Oregon. We put these trees in different geographical areas because of the different geographical environmental conditions. Some of these trees may break bud early, so they may not be suitable for production in Idaho or in Michigan. 

We find that out by putting in these trials, and that has led to an understanding of the potential that some of these species and some of these sources have the potential to make really high quality trees. 

Becky Kramer:

Are any of them on the market yet? 

Gary Chastagner:

Yeah. So we've been working on Nordmann Fir since nineteen ninety four. That's the first trial that I did looking for Phytophthora resistance. We had this project in Denmark in the late nineteen nineties, early two thousand. There has been an increased production in Nordmann Fir. As you can imagine, it takes a while. All of a sudden you can't flip a switch and next year have Nordmann Fir trees to sell. You got to get the seed. You have to grow them in the nursery for two years, maybe three years. Plant them in a field and depending on the site and how fast the species or the source that you're planting and growing. So it's a ten year process because it's been increasingly planted in the Pacific Northwest. You see the increasing amount of Nordmann Fir in the marketplace. On choosing cut farms. 

You're seeing an increasing amount of Turkish fir in the marketplace because it grows slightly faster than Nordmann fir. And more recently, we've shown that Trojan fir, which is native to the mountain regions that are going north and sort of south of Istanbul in Turkey, Trojan fir have not really been grown as Christmas trees in the past, but in our trials that we started in two thousand, and those trials showed that there was a tremendous opportunity maybe to utilize Nordmann Fir and Trojan fir because of their tolerance to a number of diseases and insects, and also because of their characteristics, their postharvest characteristics, and their foliage characteristics. 

Becky Kramer:

What accomplishments on behalf of the Christmas tree industry give you the most satisfaction? 

Gary Chastagner:

Well, I've been very blessed. I have a very applied program. We can do high tech science to help answer questions. I've always been interested in figuring out ways to solve problems. There's been some very significant accomplishments that we've been able to to help the industry. Swiss Needle cast as an example, in the early nineteen eighties, that disease was causing a three point five billion dollars loss each year. Those controls that we developed at that time cost about five cents a tree. Those controls are still widely used and they're still very effective. 

We've done similar things for other diseases, but the other aspect of it is that we were very involved early on in hosting and organizing a meeting, a professional meeting of scientists and extension people who were working on Christmas trees. It was very much scattered. People in one state weren't working necessarily with people in another state. But we hosted a meeting in the late nineteen eighties that morphed into the International Christmas Tree Research and Extension Conference. We meet every two years, and it has brought people from very diverse locations. And that meeting has helped facilitate an increase in collaborative research efforts, which are helping address issues that are the growers are facing. And consequently, it's also helping address and improving the quality of trees that consumers are getting. So those consumers are potentially getting higher quality trees because of this. 

And finally, I would say that working with students, there's a lot of satisfaction when you have students and you see that light, that enthusiasm go off and that they have successful careers. And then, of course, none of this would not be possible without the support of the staff that have had over the years and the collaboration, the support of growers that help support the project in many, many different ways. 

Becky Kramer:

Gary, I was going to close by asking how you display Christmas trees at your house. 

Gary Chastagner:

So it's changed over the years. Uh, when I first moved here and started working on Christmas trees, my wife and I would decorate a tree, put it up, and we had kids. I have two sons. Sometimes they would tag along with me and when I was doing field work. So they asked me if they could get a tree. And so one day I decided, okay, I'll, I'll harvest a couple of trees. So I harvested some like three foot tall trees. Mini trees. I took those trees home, walked in the house, and I'll tell you, it was like, this is the most exciting thing the kids had. What they liked about those trees is they were there trees. They got to decorate them the way they wanted them. And and they set these trees up in their bedrooms right alongside their bed. As a parent, you would go in there at night and you might read a story to them, and they're just laying there looking at that tree. 

Well, as a grandparent now, so I'm fortunate. I have five grandkids. The older cohort of grandkids are in the Tucson area. Well, I started taking Christmas trees, checking them in on the airplane, these tabletop trees. And so the grandkids, when they were younger, they would be waiting in the driveway for us to show up with these Christmas trees because they got to decorate these Christmas trees. And in Tucson, they would put them outside. They would decorate them outside. 

If I decorate a tree now, what I do is I also cut a larger tree and I'll put it outside, decorate it and outside our picture window. And so primarily because we're gone so much at Christmastime, traveling and visiting family. And I don't have to worry all that much about caring for it because it's a cool, moist environment and it lasts for a very long time out there. In fact, sometimes my wife will ask me in March, when are you taking that tree down? It still looks fine. 

Becky Kramer:

Did you get some funny remarks or reactions when you checked Christmas trees through luggage? 

Gary Chastagner:

[laughs] Oh, yes. These bundles of Christmas trees, they weren't necessarily in a suitcase. I would bundle them up. There'd be the base of the tree sticking out and maybe the top sticking out. And the people who were checking me in at the airport, they would say, what is this? And I would tell them that I'm taking Christmas trees to my grandkids. They loved it. So I never got hassled at all. The industry does sell tabletop trees for people who don't have as much space. Uh, aren't interested in a big tree. I do think that there would be a market if the industry promoted grandparents sending their grandkids a Christmas tree of their own. Because I'll tell you, the response that you can get is just the. It's phenomenal. 

Becky Kramer:

Gary, thank you so much for being on the podcast today. 

Gary Chastagner:

Yeah. One last thing. If you're displaying a real Christmas tree, the most important thing you can do is making a fresh cut on that base and displaying it in a water holding stand. And as a general rule, that tree can use about one quart of water per day for every inch of stem diameter. 

So if I have a tree that has a four inch diameter base to it, I need to have a water holding stand that'll hold a gallon of water after the tree is put in it. And by doing that and keeping the trees away from heat sources and stuff. You can expect trees to last for a very long period of time. Have high moisture levels with minimal, if any, needle loss. 

Becky Kramer:

Thank you so much. It was very fun talking with you. 

Larry Clark:

Chastagner was honored with a Lifetime Achievement Award from the National Christmas Tree Association in 2018. He retired in April 2025 from the WSU Research and Extension Center in Puyallup, where he also worked on ornamental flower, bulb, cut flower and nursery stock research. 

The Doctor Gary Chastagner Endowed Chair in Plant Pathology has been created and is raising money to continue research with the Christmas tree and horticultural industries. If you'd like to help, visit give.wsu.edu.

Thanks for listening to the Washington State Magazine podcast. This episode was produced by Larry Clark and Becky Kramer. Our music is by WSU emeritus professor and composer Greg Yasinitsky. [music]