Tuesday, April 19, 2011

Purple wood sedge

There are precious few people who write about sedges. That's because there aren't many people who know anything about them. Even many an experienced botanist shuns sedges, as there are so many and sometimes it seems that they all look alike. If one looks at sheer numbers, the sedges do present a stiff learning curve. In Ohio, over 160 species in just one genus - Carex - have been found.

Despite the relative lack of interest in sedges, this group plays a very important role in ecology. They stabilize soil and streambanks, form large animal-rich colonies, provide food, and not least, offer enriched aesthetics in our various habitats.

Below is some photos and info on one of our showiest woodland sedges.

A dry sun-soaked roadbank high on a ridge in Shawnee State Forest. The roadsides, which mimic natural blow-down openings in the forest, harbor all manner of interesting plants. But exposure means everything. A south-facing exposure that is often baked and sere harbors an entirely different set of flora than does a cool, shady and much moister north-facing bank. The one above sports a profusion of birdfoot violet, Viola pedata, and also is home to sedges such as oak sedge, Carex albicans, and clustered sedge, C. umbellata.

Here's the birdfoot violet, just to ensure that this post has some botanical eye candy.

This roadbank, only a mile or so away from the other, is utterly different. It sits at midslope on the hillside, and is much cooler and shadier. The soil is richer and more mesic (moist), and the plants that grow here are very different than on the sunny birdfoot violet slope. You can see some scattered tufts of greenery - those plants are our target subject

Ah, a pleasing sight indeed. This is a luxuriant tussock of purple wood sedge, Carex purpurifera, one of my very favorite sedges. I've shown this one to many people for their first time, and folks invariably react favorably to the plant. Even from afar, it's got a good look: thick tussocks of pale blue-green foliage, with long graceful culms jutting forth. Adding further allure is the fact that purple wood sedge is rare in Ohio. It is listed as threatened, and only known from a limited area of Adams and Scioto counties, although I think someone has found it in one or two other spots in recent years.

Here's how it got its name. The basal sheaths, or lower portions of the plant, are heavily infused with anthocyanins that paint the sedge a wonderfully rich purple color. To help bring order to the enormous Carex genus, it is divided into sections comprised of like species. Purple wood sedge belongs to Section laxiflorae, a group of about 25 species that are found almost exclusively in the forests of eastern North America. Some new species have been discovered in this group in the past few decades and others probably await discovery.

Sedges are probably noticed and commented on the most early in their growth cycle, as now is when the male flower spikes are copiously beset with conspicuous stamens. As it is these staminate spikes, or male flowers, that often protrude the furthest from the sedge's tussock, they draw one's eye to the plant.

Not yet quite mature, this slender spike holds the sedge's fruit, which are known as perigynia. The perigynia are slender and ellipsoid, and spaced rather widely. Each holds a small bony seed called an achene, which will later drop to the soil. Many fruits of sedges are probably carted off by ants; these insects are probably important dispersers of woodland sedges.

If you are at Flora-Quest and on one of my trips, you'll probably get to see the beautiful purple wood sedge firsthand.


No comments: