What's wrong with our Christmas tree?

December 10, 2007 8:55 PM

Is that the fire crackling? Nope, it's the Christmas tree!

We bought a Douglas fir on Saturday and tonight it has started making faint crackling sounds. Like Rice Krispies (tm). The tree is not on fire, it has plenty of water and it's not the lights making the sounds. What is it? Is the tree going to asplode? Or is it just a hive of insects that will take over my home once they're done with the tree? Please hope me!

posted by killy willy to home & garden (7 comments total)

Perhaps it's just settling.
No matter how much water you give it, it's still a dead thing now.
(I'm not judging, as I love the smell of fresh greenery.)
posted by lilywing13 at 10:48 PM on December 10, 2007

My guess is that it's just drying out. Like lilywing said, a bowl of water is no substitute for the tree's natural state. As various bits lose moisture, they become less able to bear stress and snap. Sometimes audibly.
posted by hjo3 at 11:43 PM on December 10, 2007

Once when I was a kid our tree was crackling and we couldn't figure out what was going on. Then, every morning parts of our edible decorations were eaten away - namely, popcorn garland and gingerbread men. We had a mouse living in our tree!
posted by katie at 4:12 AM on December 11, 2007 [2 favorites has favorites]

Pine beetles make crackling sounds when they are eating away at the bark of trees. That would be my guess.
posted by man on the run at 6:32 AM on December 11, 2007

man on the run: The tree is a Douglas fir, so pine beetle is pretty unlikely.
My guess would be drying out as well. Is the faint crackling constant or occasional?
posted by ssg at 8:51 AM on December 11, 2007

I'm going with drying, too, but with a particular mechanism for generating the sound.

The needles are still alive, I think, and they're continuing to transpire, meaning that water is being lost from their tiny pores (stomata). But this lost water can no longer be replaced even if you have water in a holder (because water vessels are damaged in cutting and sap congeals on exposure to air, blocking flow), and when enough water is lost, a tiny bubble appears with an audible pop in one of the water supplying tubes-- a process called cavitation. Apparently, insects can use the sound of cavitation to home in on plants made vulnerable by water stress:

Higher plant surface temperatures, leaf yellowing, increased infrared reflectance, biochemical changes, and possibly stress-induced cavitation acoustic emissions, may all be positive signals to insects of host vulnerability.

As I recall, stomata close at night, so if cavitation is responsible for the sound, it should at least be louder when the light is brightest than in the middle of the night with the decorations off.
posted by jamjam at 10:59 AM on December 11, 2007

I'd take comfort in knowing that you're not the only one. (Just search for "crackling" on the page.)
posted by iguanapolitico at 12:21 PM on December 11, 2007