Chemistry Keeps Christmas Trees Alive, For Longer Just as an avocado ripens quickly in a paper bag, bathed in the ethylene gas it releases, Christmas trees may lose their needles because of a similar "ripening" process. Raj Lada, of Nova Scotia's Christmas Tree Research Center, discusses how to block this process to prolong the life of cut firs.

Chemistry Keeps Christmas Trees Alive, For Longer

Chemistry Keeps Christmas Trees Alive, For Longer

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Just as an avocado ripens quickly in a paper bag, bathed in the ethylene gas it releases, Christmas trees may lose their needles because of a similar "ripening" process. Raj Lada, of Nova Scotia's Christmas Tree Research Center, discusses how to block this process to prolong the life of cut firs.


You're listening to SCIENCE FRIDAY. I'm Ira Flatow.

I am the last person who should talk about Christmas trees. I've never had one of my own, not even a Hanukkah bush. But I know from watching my friends with their trees that the Christmas tree might be one of the most beloved Christmas traditions. But I'm also guessing that it's also one of the most challenging. It's fun, it's festive to decorate the tree and everything.

But by the time New Year's rolls around, the tree is drying up. It's turning into a fire hazard. Every time you flick on the bulb lights, it's dropping some brown needles, left and right, all over your living room floor. In other words, it can be kind of messy, which only becomes a bigger mess when you haul it out to the curb for pickup, leaving a trail of needles. You're going down your apartment building steps. Boy, that's a trail you leave behind.

But I know you don't want to go with a fake tree, right? You got to go with a real one. Well, my next guest is he's an expert. He's on a quest to keep your Christmas tree thriving in the afterlife. I mean that means after you cut it down. A tree embalmer, so to speak.

But to keep your tree green and needled, you have to understand all the variables that make trees dry up, drop their needles in the first place. How to keep a plant that has no roots healthy - it's more complicated than you think. It's not just about keeping water in that dish at the bottom of the tree. There's chemistry involved, even hormones. Did you know that trees had hormones? Well, you will today, after I interview Raj Lada.

He's professor and founding director of the Christmas Tree Research Center. Did you know they had a Christmas Tree Research Center at the Nova Scotia Agricultural College in Truro, up in Nova Scotia, up there in Canada? He joins us by phone. Welcome to SCIENCE FRIDAY, Dr. Lada.

Dr. RAJASEKARAN LADA (Nova Scotia Agricultural College): Hi, Ira. How are you?

FLATOW: I didn't know that there is such a thing as a Christmas Tree Research Center.

Dr. LADA: Of course there is one now.

(Soundbite of laughter)

Dr. LADA: That shows the importance of the work, what we are doing, and as well as the importance of this particular issue that we are dealing with, and supporting the industry's research and development.

FLATOW: Raj, you have a new study that's out now in the journal Trees, where you were able to make trees keep their needles twice as long as usual. How did you do that?

Dr. LADA: That's true. We started with - I think the problem itself is widespread, basically. Some people talk about it, some people don't. And it started with the producer, who sent a shipment of trees to Vancouver, B.C., and turned out to be all the needless dropped, and he has not even paid the check. So that is a severe problem.

And we looked at it as a scientific approach. And any of these physiological things now, any of these abscission or flowering, everything is regulated by hormonal changes in plants or trees, basically. And this is one of it, basically. But nobody knows about it. We didn't even know that there is such a regulatory process.

FLATOW: Right.

Dr. LADA: We from our other herbaceous plants, like cotton and cut flowers and banana ripening, we know that there is a hormone that triggers and - that ages the cell and triggers the hormone level. And once the hormone level reaches to a certain point, that induces the organ shed, basically, the leaves or the fruits or flower petals or whatever it is that can abscise from their tree or plant.

FLATOW: So this is a natural hormone in the tree that sort of signals the tree to shed its needles.

Dr. LADA: Exactly. This is a natural hormone. We just call it the gaseous hormone. It's (unintelligible) natural gaseous hormone that is produced by the plant cells, basically, in response to various factors. It could be environment. It could be physical, mechanical manipulations, or any abuse, basically.

FLATOW: What's the name of the hormone?

Dr. LADA: It's called ethylene.

FLATOW: Isn't this what makes bananas ripen in a bag?

Dr. LADA: That's correct. That's what makes - makes the bananas ripe, or any fruits and flowers go to their - end their life, basically.

FLATOW: So what you have then is you have your tree ripening.

Dr. LADA: Exactly. It's almost a process. But I won't say that it's - I wouldn't say it's a ripening.


Dr. LADA: I would say more it's - scientifically, it is called a senescence process. But in these trees, basically, the senescence process is not triggered, basically. You don't see much of a change in color before the needles are shed.

FLATOW: Right.

Dr. LADA: The needles are shed even when it is green.

FLATOW: Right.

Dr. LADA: That is totally different than the ripening process that happens in other species.

FLATOW: Huh. 1-800-989-8255. We're talking about Christmas trees and how to keep them green. And maybe if you have a question you'd like to ask Raj Lada, you can ask him that question.

So is there a way then to prevent the activation of the hormone which makes the tree drop its needles?

Dr. LADA: Yeah. Now that we know that there is a hormone that is linked to the primary triggering factor, then we know how do we regulate them, how do we control them. There are a couple of ways we can do that in plants or cellular processes. One is either we can block the synthesis of this hormone itself before it is even synthesized or evolved and reaches the target. The second is if you can block the receptor that perceives the reaction of this hormone, then we can block the responses, basically.

So we were administering these two techniques, basically, and we were very successful in achieving the goal, what we wanted, to extend the needle life for a much longer period of time. It is two to threefold increase in the lifetime of the needles, basically, that hangs onto the needle - trees.

FLATOW: And how did you do that?

Dr. LADA: Well, these two are two different compounds. One is - the ethylene synthesis inhibitor is applied through water, basically, to the trees. We can dissolve it. It's a solute. It's a chemical which is available, which is used predominantly in several crops, and we can apply that to the water which we apply in the basins.

FLATOW: Mm-hmm.

Dr. LADA: And then once we allow them, basically, the tree sucks up, along with the transpirational stream. When it transpires, it reaches the spots in the needles where the abscissions takes place, and then it blocks the synthesis of ethylene. That's one technique.

The second one is - it's called an MCP, which is a gaseous thing, which you can generate the gas by dissolving the salt that will produce 1-MCP. So that is, again, while we generate the gas and allow the trees to be incubated, basically, surrounded by this gas. So this gas goes to the stomatal opening, or the pores that are in the needles, and then reaches the target spot and prevents the abscission layers to be found.

FLATOW: Hmm. Is this is something that all of us can use now, or find the ingredients for...

Dr. LADA: Absolutely. It is possible that this one works as of now, at least now in experimental stage. We have not tested this one on a fully-grown tree, basically, but that's our next step to move on. And this is the way we're going to move into a technology. We have to finalize and fine tune the concentrations, and also we'll try to develop some prototypes that will fit as an - as a storage, basically, so we'll be able to use the trees in there, to gas them up and then send them off, basically.

FLATOW: Wow. 1-800-989-8255. Tom in St. Louis. Hi, Tom.

TOM (Caller): Hi. How are you?

FLATOW: Hi, there. Go ahead.

TOM: Yes. My wife used to be a florist, and I was just wondering if they have experimented at all with glycerin, using glycerin instead of water, because I know that she would - any stemmed plant you could soak in glycerin, and it would revive it and keep it fresh.

Dr. LADA: Hey, Tom. This is Raj again. No, we have not done it. But the only problem with the trees is that the glycerin has got a higher viscosity, and that is very difficult to reach. When you mix it with water, basically, it does affect the flow of water, as well, basically.

So it all depends on the viscosity. If it is a cut flower that is only probably up to about a foot or so, well, the trees, they have to reach much taller heights, about four or five feet, sometimes six, seven feet depending on the size of the tree. So the uptake of glycerin will be a bit difficult because of its viscosity.

FLATOW: Mm-hmm. Let's talk about some of the things that people do with their trees that may not be the right thing to do in keeping them green and prolonged. First, let's talk about simply watering the tree with -as you mentioned, the dish at the bottom, is that a good idea to keep it - keep that filled and the tree well-watered?

Dr. LADA: Oh, absolutely Ira. It is absolutely essential to keep your tree watered. But watering alone is not sufficient. In our study, we have found out that the tree that drinks more water is the first one to lose needles, basically.

FLATOW: No kidding?

Dr. LADA: That is an indication that your tree is going to be losing needles faster than the ones which consumes less water.

FLATOW: Wow. So how - can you prevent that from happening, or you just water less? Or...

Dr. LADA: No, you shouldn't water less. You should keep allowing it, but that's the nature of...


Dr. LADA: ...of the beast, I would say, basically.

FLATOW: And is there one tree that loses needles, you know, that is a better kind of needled tree to have so it doesn't, you know, lose needles so quickly?

Dr. LADA: Yeah. The problem is that the trees itself is much more diverse genetically. There is no variety that is available so you can pick and use the same variety time and again.


Dr. LADA: So that is a problem. You're going for a sort of a lot, basically. If you have - it's got a tree lot and it has come from the same producer, but even from the same producer, you may not have all the trees that will have the same needle-retention properties.

FLATOW: If you could choose one, is there one that you could - you know, that would be better than the other?

Dr. LADA: If you choose the one - in terms of water consumption?

FLATOW: Of keeping the needles longer than the others.

Dr. LADA: Of course, no. We keep the - the needles that are kept for a long period of time are the ones that consumed less water.

FLATOW: And which trees would those be? Which kind of trees?

Dr. LADA: Well, in terms of the (unintelligible), basically, there are different plumes(ph) which consume different levels of water.

FLATOW: I see. I see.

Dr. LADA: There are all varieties, basically. That's what the problem is.

FLATOW: I see. And you have studied the effect of Christmas lights on trees?

Dr. LADA: Exactly. And that's another very interesting story to tell about, especially in the Christmas time. The lights, what we used, you know, people think - sometimes, we turn off the lights, and we put on all kinds of lights, sometimes incandescent lights and sometimes fluorescent lights just on top, sometimes halogen lights beaming on the trees. It looks great, but they - each one of those light spectrum is so different physiologically, and they could alter these metabolic functions critically.

So what we identified was we tried to use the recent technology, which is the LED technology, which people use it on Christmas trees all the time. We tested different spectrums - white, blue, red spectrums. And also, we had a control, which were sitting in dark, and also one other control, which were sitting in the gentle, fluorescent light and incandescent light situations.

FLATOW: Mm-hmm.

Dr. LADA: And we found that the white light has got nearly 30, 35 days better needle retention capacity compared to the dark-retained ones, or the controls with the normal lighting.

FLATOW: Wow. So did you get a whole extra month?

Dr. LADA: Oh, we have a whole extra month, basically. Significant...

FLATOW: With the white - with white - would that be like a full-spectrum light?

Dr. LADA: It is a full-spectrum LED, I would say.

FLATOW: Wow. And that's the is that part of the lights you would string on the trees?

Dr. LADA: That's important to spring, keep that white light in there, basically, especially from the LEDs. You should put more of the white lights in there, basically, rather than the other spectrum.

FLATOW: And so...

Dr. LADA: In fact, the worst performer in our experiment was the blue.

FLATOW: Wow. And so that would seem to say to me that you don't want to turn your lights off at night. You want to keep them...

Dr. LADA: Absolutely. You should not turn your lights off at night, basically. Because the reason why I'm suggesting is, as you keep them in dark, it started respiring more. And then it'll use all its carbohydrates that are in the trees, basically. And then it's - it can be starved to death, (unintelligible).

FLATOW: 1-800-989-8255, talking with Raj Lada on SCIENCE FRIDAY, from NPR, talking about Christmas trees, lots of interesting chemistry information. Let's go to Betsy in Monroe, Michigan. Hi, Betsy.

BETSY (Caller): Hello.

FLATOW: Hi, there.

BETSY: You spoke before about inhibiting the receptors for ethylene. But I was wondering about a water-reducing agent that basically keeps the stomates closed. There's a couple of them out on the market. And if ethylene has such an important role, what about the need or the - a way of reducing the water?

Dr. LADA: Betsy, thanks for asking the question. It's a very important question, basically. But the problem is just merely by reducing the water, you don't stop the symptomology of the actual triggering process, basically. So the ethylene production itself is triggered by various reasons. For example, if you have trees transported from long, far distances, then that will be triggering the ethylene production. If you shake the trees far too much, basically, then it'll produce ethylene. Ethylene can reproduce for various reasons, basically.

And water alone - we have done that, basically. We have carried the plants gently and watered them. That is not sufficient. The one which is going to or determined to lose needles will lose needles, irrespective of the amount water you provide them or you apply them. The products in the market, we have not tested, basically. (unintelligible) there are a lot of antitranspirants. But one of the with the antitranspirants is, while it closes the stomates, it also shuts down the CO2 exchange, the carbon dioxide that's required for the photosynthesis. And that's one of the things you're suggesting before with a previous person, Tom, when he asked the question about that in terms of how the photosynthesis is helping. And we need to have the sugar synthesized every single day, by the way. If you keep them in dark, that's one of the reasons why the plant dies over a long period of time.


Dr. LADA: We need the sugars. If we shut the stomata off, then it's going to have...

FLATOW: But...

Dr. LADA: ...negative effects on - it might really conserve water, but it will not keep the trees for a long period of time.

FLATOW: Right. But people are going to think, when you say they need the sugars, they should put some fertilizer or sugar in the water at the bottom of the tree. That's a no-no.

Dr. LADA: Well, that is one of the things which people talk about...


Dr. LADA: ...and we don't have much of a significant effect of that, actually, Ira.

FLATOW: Yeah. Yeah. And what is the cutting edge of Christmas tree research now?

Dr. LADA: The cutting edge is that we should have to have a tree, which is - I call that a smart tree, basically, a tree that has got a high-needle retention capacity, and it should have to have the blue-green color. And it should have fragrance, what people like. And it should have the wonderful architecture which people desire. So that's what the consumers want, basically.

FLATOW: And one last question about when you get the tree home, what's the best thing to do? Should you put another cut in the bottom of it?

Dr. LADA: Absolutely, Ira.


Dr. LADA: I think the first thing we need to do is carry it gently from wherever you bought your tree from. And, in fact, the caution should come from the producers and retailers. Retailers, if they can provide that water in there and provide them a sufficient amount of water, keep them in water, and then provide that good tree, basically, to the consumers.

And the consumers, when they bring them home, give a fresh cut, basically, at least about an inch from the previous cut - at least about an inch, basically, and then put them in water. And see that your water level is not depleted every single day and refill them, basically, with that. You - don't forget to refill the reservoir. I think that's one of the most important things. And don't turn your lights off at night. That's one other thing.

FLATOW: Keep them on.

Dr. LADA: And keep away from the kitchen. And if you can reduce your temperatures a bit lower, you can extend the needle life for a long period of time - not in 25, 30 degrees.

FLATOW: If you have a large of bowl of fruit, will it give off ethylene? And...

Dr. LADA: Yeah, of course. Don't keep your fruits close to your trees.

FLATOW: Seriously, keep the fruit...

Dr. LADA: Honestly, yeah.

FLATOW: Yeah. Yeah. Keep - if you get a fruit basket for Christmas...

Dr. LADA: Exactly. Don't even think about keeping it under the tree.

FLATOW: Don't put it under the trees. Get the fruit basket away from under the tree.

Dr. LADA: Get away. Yup. That's correct, actually, Ira.

FLATOW: And there you have it.

(Soundbite of laughter)

Dr. LADA: Absolutely. Absolutely.

FLATOW: You know, what better tips could you have for Friday afternoon? Thank you very much, Raj, for taking time to be with us.

Dr. LADA: Not a problem, Ira. Pleasure.

FLATOW: You're welcome. Raj Lada is a professor and founding director of the Christmas Tree Research Center at the Nova Scotia Agricultural College in Truro, Nova Scotia, up there in Canada. You now know what to do with that fruit basket.

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