Sedges (Carex, Cyperus (Umbrella Sedge), Eleocharis (Spike Rush), Schoenoplectus (Naked Stem Bulrush), Perigynium, Tubercle)

By Bruce Homer-Smith

Sedges have edges – most sedges have triangular stems. If you run your hand along the stem, you can feel the three edges. Occasionally, a sedge stem will have four edges or be round. Stems are solid (filled with pith) and erect.

Here are some other sedge characters:

· They’re often found in bogs, swamps or meadows along streams.

· Sedges generally have long, quite narrow leaves.

· Inflorescences vary, as you’ll see below. In California, all sedges are wind pollinated.

· Sedge flowers do not have petals (rushes do).

California has seven genera of sedges. Here’s how to distinguish between the major ones.

Carex

Carex is the most common sedge genus. Separate male and female flowers appear on the same plant, sometimes on the same spike and sometimes on different ones. Stems are triangular in cross section.

Two Tooth Sedge (Carex serratodens)

Photo by Steve Matson

Black Alpine Sedge (Carex nigricans)

Photo by Steve Matson

Carex female flowers have a perigynium - a hard sac that completely surrounds the pistil except for a pore at the top, which allows the stigma to stick out so it can receive pollen. If you find this structure, you know you’re looking at a Carex.

Cyperus – Umbrella Sedges

Cyperus flowers are generally bisexual. They don’t have a perigynium or tubercle. Stems are triangular or round in cross section.

Tall Flatsedge (Cyperus eragrostis)

Photos by Wilde Legard

Cyperus inflorescences are umbel-like. In Tall Flatsedge, above, a large umbel has flat leaf-like bracts that point sideways. Secondary umbels are made up of two-ranked spikelets.

Here are two other species of Cyperus, also showing the umbel organization and flat groupings of spikelets.

Papyrus (Cyperus papyrus)

Photo by Ron Vanderhoff

Black Alpine Sedge (Carex nigricans)

Photo by Steve Matson

Eleocharis – Spike Rushes

Eleocharis is derived from two Greek words meaning “graceful marsh dweller”.

This sedge is confusing – it has “rush” in its common name and has round stems, but it is not a rush. The flowers hide behind scales, like a sedge, and are not six-parted like rushes.

A single spikelet appears at the top of the stem. In general, it’s a spiral of many scales, each covering a bisexual flower.

Parish’s Spike Rush (Eleocharis parishii)

Photo by Steve Matson

As with pine cones, the scales cover developing flowers. When mature, both male and female reproductive parts emerge from the scales. Fruiting seeds grow a distinctive cap, called a tubercle.

These features are pretty strange, so here are some more examples to help you get the idea.

Broad Spiked Spikerush spikelet

Eleocharis obtusa

Photo by Keir Morse

Pale Spike Rush spikelet

Eleocharis macrostachya

Photo by Wilde Legard

Four Angled Spikerush spikelet

Eleocharis quadrangulata

Photo by Steve Matson

Four Angled Spikerush fruit

Eleocharis quadrangulata

Photo by Steve Matson

Notice that the reproductive parts are quite naked when they emerge from their protective scales.

Although there are leaf sheaths at the base of stems, Spike Rushes have no leaf blades.

Small Spikerush (Eleocharis parvula)

Photo by Wilde Legard

Every green stem you see here ends up with a spikelet at the tip.

Schoenoplectus – Naked Stem Bulrush

This genus includes two very large, common California marsh plants – California Bulrush and Tule.

Stems are round or triangular, and often ribbed. This genus has basal leaves, plus maybe one leaf along the stem. Leaf blades exist, but they may be short.