Are You Mis-Using These Common Tree Terms?

Sep 25, 2017

As I split and stacked my winter firewood this fall in preparation for the long nights to come, trees in the surrounding forest were also preparing for winter. While I watched their leaves turning yellow along the flank of the Bitterroot Mountains, I found myself considering the confusing terms people use to describe those trees. In particular, folks tend to mix up perfectly good words in ways that leave me more befuddled than enlightened.

Some write of “conifers and deciduous trees” as if they are somehow different. But, of course, when describing trees, the words "coniferous" and "deciduous" may be distinctions without a difference.

Attempting to classify trees using a division between "coniferous" versus "deciduous" is like trying to separate animals into those that lay eggs versus that that hibernate over winter. It just does not make sense.

In other words, the writers are trying to contrast a method of sexual reproduction with a habit of becoming dormant. In fact, many cone-bearing plants have the deciduous habit of losing their leaves in the winter.

The western larch and alpine larch trees in the Bitterroot Mountains are examples of such deciduous conifers. That is, they are cone-bearing trees that shed all their leaves each fall and grow new ones the following spring — as do the bald cypress and tamarack trees back east.

Unfortunately, the term deciduous is also often incorrectly used, because not all broadleaf trees are deciduous — for instance, holly, magnolia, many oaks, and various tropical species are broadleaf evergreen trees that do not shed their leaves in winter.

The logic used by landscape ecologists who deal with such descriptions is to make the distinction first on leaf type: that is, needleleaf versus broadleaf; and then on leaf persistence: evergreen versus deciduous; and to disregard the method of reproduction. Sex — as in bearing cones and being coniferous — is irrelevant for tree identification, so that larch can be described simply as a needleleaf deciduous tree. Ponderosa pine is a needleleaf evergreen tree. Aspen is a broadleaf deciduous tree, and holly is a broadleaf evergreen tree. A forest stand containing ponderosa pine, Douglas-fir, and western larch is a mixed needleleaf forest.

So, when you go into the forest this winter, try to overcome the stereotypes learned in grade school and see western larch as what it is—a deciduous tree that has shed its leaves for the winter just like the cottonwood did.

And let’s hope that the person looking for winter fuel will realize that the larch tree without needles may still be alive and not yet ready to become firewood.

We have a long way to come in overcoming racial stereotypes, and I’d like to see us do the same with tree stereotypes—even after a long history of misuse.

"Field Notes" is produced by the Montana Natural History Center.

(Broadcast: "Field Notes," 11/10/15. Listen on air or online Sundays at 12:55 p.m., Tuesdays at 4:54 p.m., and Fridays at 4:54 p.m., or via podcast.)