Commentary by Roger Martin Martin writes about research at KU for Kansas media and in a Web zine. Contact Martin at rmartin@kucr.ku.edu or (785) 864-7239. Martin also can be heard on KANU 91.5 FM public radio Archives More articles by Roger Martin Subscribe now to receive KU News by email

The science of Christmas trees

by Roger Martin

Here I go again, not feeling Christmassy.

Of course I'd like to feel Christmassy, just like all the other 57-year-old men who finally had an up year in the stock market and whose prostate exams and colonoscopies went well.

I did feel Christmassy that one year I nailed a small cedar tree to a board and put it up in the bay window. If memory serves -- and at this age it is more likely to desert me -- I even draped the scruffy little thing with colored lights or tinsel or something.

It was one small step toward recovering from that screaming match my brother and I had about whether our parents had spent more on HIS Lionel train set or MY Gilbert chemistry set -- and one giant step for Christmaskind.

At least I'm not alone in not feeling Christmassy. Last year, for example, only one out of five U.S. households had a real tree. Thirty-three percent, like me, had none.

If you're among the 21 percent who do the real tree, you need to know a few things about that puppy.

For example, you should know that that is one ancient tree species you've taken into your home. The cone-bearing spruce and fir -- the most popular trees used in this season -- along with cedar and pine are all conifers.

The conifers fit under the scientific heading "gymnosperms."

Trees that are gymnosperms produce naked seeds. The angiosperms -- oak and maple trees, for example -- produce seeds tucked inside of ovaries.

The angiosperms have been around 160 million years, the gymnosperms three times that long.

My source, Craig Martin, a University of Kansas professor of ecology and evolutionary biology, tells me the distinctive odor of a Christmas tree -- I mean a REAL tree of the type that Christmassy people buy -- comes from compounds that are the source of turpentine.

That's right: When you put up a Christmas tree, you're filling your house with the odor of paintbrushes being cleaned.

Go ahead, sniff the darned thing. That's terpene, my friends, a straight-chain hydrocarbon molecule.

Now, when you look at a pine needle, you probably don't think to yourself, "What a beautiful leaf!" But you should. Because that's what a needle is. And it's a tough leaf, at that -- tougher than an oak or maple leaf, say, for several reasons.

Both a broad leaf and a needle are coated with wax to prevent water loss, but the needle's coat is thicker.

The walls of the cells that make up the needle are also thicker. Inside those cells are fats and enzymes with special sugars stuck to them that are a little different from the constituents in broader leaves.

All these factors, Martin says, guarantee that conifer needles can weather a rock-hard freeze.

Do Christmas trees grow naturally in Kansas? I ask Martin. He says no, adding that the kind of conifer I once harvested wasn't really a cedar either.

It may be called a red cedar but it's actually a juniper, he says.

Then he adds, "Many people, including some botanists, call it a weed because one definition of a weed is a plant that colonizes disturbed, open places."

So there you have it. The only year in my adult life that I thought I'd put up a Christmas tree, I actually put up a Christmas weed.

Figures.