You have walked on them, looked at them, maybe even pulled the seed stem to nibble on the tender base, as though it were a grass. But it isn’t.
Sedges are an important, often overlooked group of native plants. In Iowa there are at least 125 species belonging to one genus, Carex.
Carex sedges often are overlooked because they look so much like grasses. And with wide variation in their appearance and very tiny details, they are a daunting group of plants to learn. But with patience, those details also lead to small moments of awe and wonder at the different symmetries and adaptations of each.
Wet sedge meadows “wave” in the wind. Engeldinger Marsh, Polk County, South Skunk River
Sedges provide food to several kinds of native birds, insects, and rodents. Their roots help hold topsoil in place. They are used by botanists to identify ecosystems and plant communities, and by wetland restoration specialists to diversify the vegetation.
These plants occur in every kind of ecosystem imaginable in Iowa: the dry tops of the Loess hills, the shallows of ponds and lakes, established remnant prairies and woodlands, and recently disturbed ground. To begin the challenge of identification, your familiarity with a few technical terms and plant parts is helpful.
The most essential part of a sedge to know is the perigynium (pear-uh-GIN-ee-um), which is a sedge’s seed and its outer husk. The mature perigynium (mid-June to mid-July for most) provides the most reliable clues to the species. It encloses the seed, which is not visible unless the husk is opened.
In addition, identification of sedges is based on: 1) habitat, 2) the arrangement of female and male flower spikes on the stem, 3) the orientation of the perigynia along the stem of each spike, and a few other features.
For example, a sedge that grows in a permanent wetland and sits atop a small hummock of soil is one of only a few species, so habitat and growth pattern narrow the choices. A short sedge that appears in April or May in woodlands, flowers during that time, and sheds its seeds (perigynia) in late May almost certainly is Pennsylvania sedge (Carex pensylvanica), common in the state’s wooded ravines and slopes.
The male and female flowers are not showy, but on close inspection they can be very attractive. Generally the stamens (pollen-bearing parts) are creamy white, while the styles (female pollen receptors) are white and inconspicuous. Immature perigynia are usually green, but some are dark burgundy or other colors. After flowering, you’ll become familiar with the female spikes and the male spikes as the male flowers dry and turn tan or brown.
Above are an unidentified wetland sedge, Fox Sedge (C. vulpinoidea), and Pennsylvania Sedge (C. pensylvanica) in bloom. In bloom most are nearly impossible to tell apart, with habitat and several seasons of observation are the best guides.
Along the flowering stem, male and female spikes can be separate, usually with male spikes (one or more, depending on species) at the end and female spikes below them. Another common arrangement is for each spike to have both female and male flowers, and the female flowers may cluster either closer to the base or closer to the end of the spike, again depending on species. Each spike may or may not have its own stem, that is, spikes may stand away from the main stem, they may droop on a long stem, or they may lack stems and hug the main flower stalk.
A long, thick spike of perigynia that looks bristly like a bottle brush (made of the long “beaks” on the perigynia) also is one of only a few species, and here the orientation of those beaks and the perigynial features are helpful. Do the bristles all point toward the end of the spike (C. vesicaria)? Are some perpendicular to it (C. hystericina, C. lurida)? Do some actually point backwards, toward the base of the spike (C. comosa, C. retrorsa)? There also is a good chance that these sedges grow in moist to wet soils and along the edges of lakes, ponds, and wetlands.
These are Carex vesicaria and C. hystericina (Porcupine Sedge), both with inflated perigynia. The bristles or beaks are long, all pointed to the end of the spike in the first, or with those nearer the base pointed at a right angle in C. hystericina
Now for those perigynia. You will want a jeweler’s loupe, preferably with 20x magnification. A basic 20x loupe costs only a few dollars. The true seed of all sedges is inside a husk that varies widely in size, shape, and other features. In most cases you need to look only at the husk, not the seed inside.
A commonly found Iowa sedge of moist prairies is C. molesta, Troublesome Sedge. This and several similar sedges have a flattened or winged perigynium, with a bump at the base or near the center of the flat part, in which rests the seed. At the other end, a “beak” ends away from the stem and may have remnant flower parts. C. molesta has its bump at the base, the flattened perigynium is more or less round, and the beak has two tiny “teeth” at the end. When the perigynia are mature, several raised nerves or veins are obvious with the loupe on the side that faced out in the spike.
The flattened, circular perigynia of C. molestsa, with a short beak that supported the styles.
The next photos show close-ups of perigynia and female spikes of some sedges. Notice the different arrangements of perigynia, from scattered to dense, and the differences in shape and absence or presence of a beak. One spike shows a species with no beaks, whose perigynia are arranged like “grapes on a string.” This is C. grisea, a fairly common species of open, damp woods. Notice how the perigynia are widest toward the flowering end, not toward the stem. They have round cross-sections, unlike the flat or concave perigynia of C. molesta and others.
Carex grisea has perigynia that are wider above the middle and are arranged like tiny “grapes on a string.”
A spike of C. sprengelii or Long-Beak Sedge shows how the very long, thin beaks extend from a large, rounded perigynium. Also, the styles remain on the beaks. While not a wetland species, it does have inflated perigynia, grouped rather loosely in a spike that droops from a long, thin stalk.
C. rosea is a delicate plant of Iowa woods; the perigynia are in scattered groups, with beaks about half as long as the body. With the loupe, the two styles are curled like the horns of a ram, a giveaway for this species.
Let’s end with an easy sedge, found in wet woodlands, but not in standing water. Each stem bears only one cluster of perigynia, and these have the unusual appearance of the ancient weapon, the mace. One common name is Mace Sedge. If you spot it, there really is no mistaking the round, spiky ball, an inch or more across. The perigynia are like those of wetland species, full of air and able to float. Gray’s sedge (the other common name) doesn’t grow in large colonies, and it is not as common as other species, so it may be overlooked.
It simply stands to reason that any genus of plants that has so many species, so many different ecosystems, and is so abundant warrants attention from plant people.
A basic rule is this: if the stem has a triangular cross-section, it’s a sedge, not a grass, and it might be one of the Carex sedges.
Let your explorations of genus Carex begin.
Leland Searles, or “CompassPlant,” has a business, Leeward Solutions, LLC, that provides ecological consulting services, including regulatory wetlands and endangered species evaluations, and private botanical inventories and related work. See the web site link near the top of the blog.