Scratch-and-Sniff Trees

A few trees have a distinct smell that can help you identify them. Out west, if you dig your nose into the bark furrows of a Ponderosa pine, you might a whiff of butterscotch. Here in Wisconsin, scratch at the bark of a black cherry and the odor of bitter almonds may make you cough. My favorite local tree with an unexpected smell, though, is the yellow birch (Betula alleghaniensis). Peel back its bark, sniff, and what you’ll smell is the fresh, minty scent of wintergreen. This is one foolproof way of distinguishing it from its cousins the paper birch and hophornbeam, which we also have here.

Oil of wintergreen is an organic compound produced by a number of plants, probably to deter herbivores. This is the stuff that makes wintergreen lifesavers spark, thanks to triboluminescence. (If you have no idea what I’m talking about, go into a dark room and look in a mirror while chewing up a wintergreen lifesaver with your mouth open. You’re welcome.)

Other plants also produce oil of wintergreen as well – we have its namesake plant, wintergreen, here, which is a small forest floor plant with red berries and shiny dark green leaves, and there’s another birch species elsewhere on the continent, sweet birch, that smells even more strongly than yellow birch.

What plants can you identify by smell?