Winter Plant Puzzle

by Carl Strang

Today we return to winter botany, focusing on four species that are connected to one another in ways that are instructive, if not obvious. All grow in the same spot, Mayslake Forest Preserve’s south stream corridor prairie. It’s a fairly low area, and is enjoying considerable improvement thanks to Mayslake’s volunteer restoration crew. Let’s start with the common water horehound.

This plant stands a foot tall or so, and likes its feet wet. The clusters of spiky fruits radiate out from spaced points along the stem.

Here is what it looks like when flowering.

The common water horehound is not an imposing plant in flower.

Next we’ll move on to yarrow. Here is its winter form.

The various species of genus Achillea figure prominently in the folklore of Europe and Asia.

And, in bloom:

Yarrow is an attractive plant. The leaves have a fernlike featheriness.

Finally, let’s take a look at mountain mint (two species occur in this prairie; they are so similar that the photos work for both).

One easy way of distinguishing the common and slender mountain mint species is by presence or absence of a strong minty odor and flavor. I found that the dried and shriveled winter leaves of the common mountain mint hold that flavor.

Their flowers are identical or nearly so.

The mountain mint flowering period goes on for a long time in summer.

OK, so I’ve shown you the three genera (for present purposes placing the two mountain mint species together). Now the question is, which two are most closely related phylogenetically?

Superficially the nod would go toward placing the yarrow and mountain mint together, because at first glance their overall shapes are very similar. As it happens, though, the common water horehound is in the mint family, and so yarrow (a composite) is the odd plant out. One feature that separates yarrow from mints in winter is that yarrow has alternate leaves, while mint leaves are opposite (visible in the above photos). Let’s finish by enjoying close-up looks at the dried heads of those two superficially similar plants. Yarrow first:

Winter yarrow heads look like beautiful little pale cones.

Now, mountain mint.

The perforated look of the little mountain mint heads reminds me of the larger ones of wild bergamot, which is yet another member of the mint family.

That may be it for this year’s installment of winter botany, unless we get some well timed fresh snow to provide a backdrop.

1 Comment

  1. January 22, 2013 at 6:59 am

    […] I was biding my time until we had some snow to provide a backdrop for photographing winter plants, but then learned that I can adjust the aperture on my Olympus point and shoot camera, and use that to blur the background. Today’s resulting focus is on four species of composites. Beginning in the damp portion of the south stream corridor prairie at Mayslake Forest Preserve, I was struck by the superficial similarity of wild quinine fruiting stems to those of the mountain mints. […]

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