Man at the vet’s office: “Doctor, my dog doesn’t have a nose!”
Vet: “Goodness! How does he smell?”
I love that old gag, and so do my students. I tell it as often as I can get away with it, invariably when I am trying to get across to the students the fact that a particular plant may have a particular and characteristic smell. I figure that if you are learning a new species, and if you can associate it with a distinctive scent, then it ought to be able to remember the name, as long as you can properly smell the plant.
Now, smelling plants happens all the time, but most often, people think that the only parts of plants that deserve to be smelled are the flowers. Not so. Various other organs of plants often reveal an odor, whether pleasant or stinky. Roots, stems, and leaves may all figure into this situation, depending, of course, upon the species.
Of course, there’s not too much to smelling a flower: you just put your nose down (or up) to it, or a bunch of them if small, and inhale. This technique usually works well, but of course some flowers have essentially no fragrance (or smelliness) at all. (And, some flowers will give off their fragrance at a certain time of day only.)
However, smelling other parts of a plant may not be so easy. I commonly ask the students to smell the leaves of a plant … and they generally hold the fresh leaf up to their faces and inhale. That’s not going to work. The best way to get whatever smell might characterize foliage is to take several of the leaves, gently crushed, and warm them inside a fist. Hold your closed fist up to your nose, and gently inhale. This works for roots, too. And if you want to see if a stem has a scent, you can gently scratch a twig (needs to be living, though), using the scratch and sniff technique.
This week’s Mystery Plant, Artemisia vulgaris, or mugwort, is a really smelly one. It is a complete weed, and it grows basically all over North America, except for the southwestern USA. It is originally native to Europe and western Asia, and is thoroughly naturalized in North America; in fact, it has probably been introduced a number of times into this continent, with the various populations hybridizing and backcrossing with other willy-nilly. It is a really variable species, but always seems to show dissected leaves which are green above and softly pubescent (white or gray) below. Its flowers are tiny, held in heads, and scattered up and down the top parts of the plant. It’s starting to bloom now, and will keep doing so until it gets cold. It commonly grows in dense patches in very weedy places, sometimes getting 2-3 feet tall.
And its smell: to me it’s a strong form of what you get when you start playing around with the foliage of mums. Very memorable.
EDITOR’S NOTE: John Nelson is the curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia, S.C. 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196, or email firstname.lastname@example.org.