An Introduction to Carex, Specifically of Wisconsin.
Delving into the nearly 200 species of Carex of Wisconsin was, for me at first, a daunting task. The first challenge was to learn to distinguish Carex from the rushes and grasses. This distinction is a challenging one, and one which I have made mistakes with (argh) even after many weeks of collecting and studying. One cannot make the mistake of relying upon a single characteristic, such as "rushes are round, sedges have edges," because, often enough, and as in this case, Carex will not actually have edges. Hence, a better approach is to utilize a suite of characteristics. The figure below outlines the key characteristics of Juncaceae, Cyperaceae, and Poaceae.
Taken from a rough draft of Introduction to Sedges (Carex: Cyperaceae), by Andrew Hipp.
With this, one has a fairly simple method for the determination whether or not what he or she has in hand is indeed a sedge. If the plant is three-ranked, has fused sheath-margins, a ligule, in many cases partly fused to the blade, a single scale below each flower, unisexual (bisexual) flowers, and a hard achene, one can be fairly confident that it is indeed a sedge! In most cases, due to the large volume of Carex within the state, this sedge will be a member of the genus.
When determining the species of Carex, many different identifiers are necessary. Here is a short list of the usual suspects starting from the base of the plant and working progressively upwards to the inflorescence and then into it. Work with me.
Sheath: part of the leaf that enwraps the culm or other leaves. Broken into the dorsal sheath (continuous with the blade), and the ventral sheath (opposite the blade).
Ligule: a small flap of tissue that arises on the inside of the leaf base at its juncture with the dorsal sheath. An important identifier.
Culm: the flowering stem of a sedge.
Spike: the inflorescence. When compound, made up of spikelets.
Scale: a bract that subtends a flower. The pistillate scales of Carex are important identifiers.
Perigynium: a sac that encloses the female flower, and, when ripe, the achene. Perhaps the most important feature of Carex as an identifier, especially since this structure is restricted to Carex in the Wisconsin flora.
Beak: a slender extension of a perigynium or achene. An important identifier.
Nerve: a vein in a perigynium or scale.
Achene: the actual fruit enclosed within the perigynium.
I cannot overemphasize the importance of using a wide variety of sources when working with Carex. Different perspectives of the genus have helped me throughout this summer. They include books, websites, herbaria, and certainly most beneficially, others who have already worked with Carex. Here is a list of (hopefully) everything and everyone that has helped me.
Flora of Michigan, Volume I. Edward G. Voss. This is the book I used to do most of my keying.
The UW Madison Herbarium and its website, http://www.botany.wisc.edu/herbarium/, has been critically important.
Andrew Hipp. The Hippster has been my guide, my contact, and my mentor for the last three-and-a-half months. Without him, this project would have gone nowhere. He lurks about in the Herbarium.
Ted Cochrane. Mr. Cochrane, as the curator of the Herbarium and another sedge-master has been extremely helpful in identification, mounting, and other matters.