Sedges Have Edges: Carexes in the field

The family Cyperaceae, the sedge family, has an evil reputation. It is considered a difficult group of plants to identify, even to the family or genus level, and especially to the species level. The genus Carex is particularly thought to be a tough group to identify. Many people, including biologists who survey the wetlands where Carexes like to grow, simply lump them as 'Carex sp.'--meaning they know they are a Carex, but have no idea what the species is.

Carexes are not showy in the 'garden flower' sense. They lack big, colourful, showy petals and instead they are typified by the presence of spiky flowerheads made up of clusters of flowers that are usually a drab brownish-green in colour. But they are showy in their own way, architectural in appearance, with somewhat attractive patterns. Once you get used to the way Carexes look, you can begin to spot different species wherever you go. After a while, it is fairly easy to recognize the genus. The stems do have edges, and are triangular in cross-section. The leaves look grasslike, although they are usually a different shade of green than most grasses. And, importantly, they like wet areas--ponds, streambank, creeks, lakes, ditches. If it's grassy looking and growing in a wet area, think "Carex". Carexes are primarily freshwater species, but they will also grow in brackish lakes and ponds. In the Fraser Delta, they are also found in places like Ladner Marsh, or Finn Slough, areas that are subject to the daily tidal flux and brackish water.

The seeds, or peryginia, of Carexes, are the most important features for identification, and this is where the evil reputation comes into play. For the most part, they need to be examined under a microscope, and measured (in millimeters). The size and shape of the perigyinia (including the length of the beak), and the number of stigmas present in each flower, are critical in separating species. This isn't actually as bad as it sounds. The differences can be small, literally, but once you get used to the parts of a Carex, and become familiar with their shape and variation, many Carexes can be identifed to species. And, if not, they can be identified to the 'group' they belong to. But there is one, big, caveat to this: most taxonomic keys for this group are based on ripe fruit--fruit that are full-sized. To identify Carexes with any certainty (unless you already know the species well), you must have plants with mature fruits. Plants with immature fruits, or plants in flower, can be a challenge to identify. If not impossible.

Difficulties aside, some Carexes are instantly recognizable because of their large flowerheads, or distinctive shape or unique habitat. The photos below show some of the more easily identified species. If you see these in the field, you generally will be able to put a name to them. They all have big flowerheads, and are common in their preferred habitats. Click on the links to view distribution maps and more photos.

Carex macrocephala (large-headed sedge) is very distinctive, growing in low dune slacks and sporting very large flowerheads for the size of plant--which is actually fairly small.

Carex comosa (bearded sedge) is another distinctive one, these flower heads dangle, and are fairly large. Importantly, though, this is a species that prefers very calcareous growing conditions, such as those found in Cheam Lake, which is a marl lake.

Carex lyngbyei ssp. cryptocarpa (Lyngby's sedge) is a very common species that forms extensive homogeneous expanses in coastal areas in BC, including along the Fraser river, in the shoreline meadows that are also filled with orchids, bog buckbean and, unfortunately, purple loosestrife.

Carex stipata (awl-fruited sedge) is another very distinctive species, with relatively large flowerheads that are somewhat triangular in shape. It is very common in the Fraser Delta, and is found in almost any wet patch, ditch or creek edge in the area.

The genus Carex is the largest genus in the sedge family and one of the most important plant groups for waterfowl. Many ducks feed on sedges, in particular Carexes, and this genus, along with the spike-rushes (Eleocharis species), are common in wetlands throughout BC, sometimes occurring in large homogeneous stands.