How to ID Sedges

Sedges often remain a mystery for many of us. This year, the Prairie Bluff chapter of The Prairie Enthusiasts had an outing at Abraham’s Woods for the purpose of learning how to ID sedges. This morning workshop was lead by Nate Gingerich and John Larson.

Sedges are mainly found in moist soil in full sun although there are also many species that enjoy woodlands and dry bluffs. You’ll find them in flower mostly during the months of April, May, and June. Sedges are differentiated from grasses by a number of characteristics, but the simplest one is the stem. A sedge stem is triangular and solid; a grass stem is round and hollow. There are some sedges that are annuals but all the of the Carex species are perennial. Whether you can ID the sedge or not, the good news is that you are very unlikely to encounter a non-native sedge species.

Some of the important things to take with you when you go out to ID sedges are:

• A 10x loupe
• A good field guide or two
• Know the terminology and structural parts of a sedge. This takes times but it makes working through the dichotomous keys much easier!
• Have a good metric ruler. Many of the IDs are dependent upon an accurate measurement. A millimeter or two can change the ultimate identification.
• Take a plastic bag. This will keep whatever you collect fresh. When you do take specimens from the field, be sure to take 2 or 3 leaves and seed heads from the same plant.
• Know the habitat. It helps to know where to look for sedges and also when you collect a portion to ID, make a note of the habitat. Sedges are mainly in moist soil but there are some that grow in woods and on dry, rocky bluffs. Knowing where the sedge is found can narrow down the ID.

Once we worked through a few IDs using the dichotomous keys, we found there are a few specific areas that need to be a focus. Here’s the list of some of the key elements that need attention.

• Basal leaf sheath – what color is it? Green or brown/purple? This is often better determined in the field than on a specimen removed from the field.
• Back side of the leaf sheath – look for distinctive veining
• Top of front side of leaf sheath (summit of leaf sheath- look at shape and texture. Is it firm, flimsy, clear, green, spotted, etc?  Does it end in a concave, convex, or straight line?
• Spike shape and configuration. Particularly try to determine how male and female flowers are arranged- are they on separate spikelets or are they combined in the same spikelets, and if combined which are on top and which are below?
• Stigma numbers and shape
• Habitat and location – it helps to know what county or part of a state the sedge is found
• Plant growth – it is clumping or not?

A few resources include:

• Field Guide to Wisconsin Sedges by Andrew Hipp
• Spring Flora of Wisconsin by Norman Fassett
• Sedges: Carex by Robert Mohlenbrock
• Sedges: Cyperus to Scleria by Robert Mohlenbrock
• Woodland Carex of the Upper Midwest by Linda Curtis