How to ID Sedges

Sedges often remain a mystery for many of us.  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. 

John Larson and Nate Gingerich

John Larson and Nate Gingerich led a field trip and offered the following tips.

Equipment you’ll need with you:

  • 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. 

7 key elements that need attention

1. Basal leaf sheath

What color is it? Green or brown/purple? Basal leaf sheaths are described as purple/brown and green. This is often better determined in the field than on a specimen removed from the field.

Sedge ID

2. Back side of the leaf sheath

Look for distinctive veining; does the leaf sheath has interesting or unique lines?

sedge ID

3. Spike shape and configuration

Particularly 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? Scales, bracts, and leaves can be easily mistaken. Beaks can be in different shapes.

Sedge ID

4. Stigma numbers and shape

Stigmas can be curled in a couple of shapes and can have more than one.

Sedg ID

5. Summit of the leaf sheath

Look at the shape and texture of the top of front side of leaf sheath.  Is it firm, flimsy, clear, green, spotted, etc?  Does it end in a concave, convex, or straight line?

Terminal and lateral spike, leaf sheath, peduncle

Plant growth

Is it clumping or not?

Carex blanda

7. Habitat and location

It helps to know what county or part of a state the sedge is found

Additional Resources

  • 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