Sorting out Grass Like Plants
Grasses, Sedges, and Rushes

More than any other group of flowering plants I find that people get quickly confused trying to distinguish Grasses, Sedges and Rushes. Using the rhyme 'Sedges have edges; rushes are round; grasses are hollow; what have you found?' helps sort out most of the differences but there can still be some confusion.

There are a small number of other families with only one or two representative species that can also be confused; it is helpful to be able to recognize these three additional groups: Typhaceae - cattail, Sparganiaceae - bur-reed, Acoraceae - sweet flag. These are aquatic plants with a compact flowering head at the end of a stem (like a corn-dog in Typha, and a mace in Sparganium), or off to one side in Acorus. Typha and Sparganium have two ranked leaves from the base.

All of these groups broadly resemble grasses having long, narrow, parallel-veined leaves and inconspicuous flowers. Looking at the stem structure will generally allow you to separate out each of the groups.

  1. Poaceae (Grasses)
    Stem almost all hollow, round or sometimes flattened, with joints. Joints or nodes are solid and typically swollen. Single seed in each flowering scale. Margins (edges) of the leaf sheath are open, but may overlap. Usually a ligule (membrane or tuft) where the leaf meets the stem.

    Adapted from Ontario Weeds, 2010, ON Gov.

  2. Cyperacea (Sedges)
    Stem solid and mostly triangular but some round or square, no joints. Pith of stem may be loose and appear hollow if not carefully cut. Single seed in each flowering scale. Leaf sheath is closed or fused. Often a ligule (membrane or tuft) where the leaf meets the stem in a U or V shape. Leaf often has a W shape or is apparently lacking (e.g. Eleocharis or Schoenoplectus). Genera included: Carex, Eleocharis, Schoenoplectus, Scirpus, Eriophorum, Cyperus

    Adapted from Ontario Weeds, 2010, ON Gov.

  3. Juncaceae (Rushes)
    Stem solid and mostly round. Several seeds in each pouch. Regular flower made up of 3 outer and 3 inner scales and 1 pouch. No ligule. Margin of leaf sheath is closed. Generally leaf is inrolled. Genera included: Juncus, Luzula.

(Adapted from: Budd's Flora of the Canadian Prairie Provinces, Looman and Best, 1979)

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Email: Last modified: Sat Oct 23 07:12:33 2010