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What is a Sedge?

Posted on 6/22/2015 by State Nature Preserves
Sedge Meadow Owens Fen SNP

Sedges. The mere mention of these grass-like plants can make even the most enthusiastic of plant lovers furrow their brow. That comes as little surprise due to the complexity and excruciating similarities this unique family is known for. But have no fear! This post is designed to open your eyes to the beauty and aesthetic details of this often shunned group. Other monocot relatives like trillium, orchids and lilies might have the wow factor but the sedges are wonderful works of art too. You just have to look past the intimidating aura that surrounds them.

Fibrous-rooted Sedge (Carex communis) in flower in the early spring

So what exactly is a sedge? Many might overlook them as an odd species of grass but they are completely different plants in their own family, the Cyperaceae. Their flowers are reduced like a grass and thus not very showy. Almost all sedges are monoecious with both male and female flower parts on the same plant. Looking at the photo above you can see the yellow pollen-laden male stamens above the clear, thread-like pistillate flowers. Due to having small, inconspicuous flowers, sedges rely on the wind rather than insects/flies for pollination; which is why the male staminate spikes are set above the female flowers.

Buxbaum’s Sedge (Carex buxbaumii) in fruit

One of the most common phrases to help differentiate a sedge is, “sedges have edges”. This refers to members of the family having triangular stems as well as three-ranked leaves. Grasses have round stems and two-ranked leaves. Of course, there are exceptions to the rules but overall this one holds up quite well. Perhaps the best means of identifying a sedge is when they are in fruit. The fruiting bodies of sedges are small, hard seeds called achenes. Additionally, the true-sedges from the genus Carex enclose their achene in a papery sack known as a perigynium (plural: perigynia). The number, size, color and shape of a sedge’s perigynium varies widely and combined make up the spikelet. This structure is often times the best means to identify which species you have.

Acidic flatwoods full of Greater Bladder Sedge (Carex intumescens)

The diversity of the sedge family is dizzying. In Ohio alone there are 250+ species from 16 different genera. The aforementioned Carex genus is by far the largest with 160+ species native to our state. No other genus comes close to having that many representatives in our flora. Members of Cyperaceae come in a nearly endless parade of different shapes and sizes. Some are so minute you need a hand lens to accurately inspect the plant, while others can be taller than you and occur in large, sprawling colonies.

Line up of different Carex sedges from a swamp woods in Lake Katharine SNP

When it comes to sedges diversity really is the name of the game. They grow in just about any habitat you can think of; from high-quality fen meadows, to a disturbed, weedy dirt lot along the road. They occur in their densest and most impressive numbers in wetlands but thrive just fine in high and dry forests, prairies and fields too. The photo above is a lineup of different Carex sedges all from a single high-quality sweetgum/river birch swamp woods in Lake Katharine state nature preserve in Jackson County. It goes to show how morphologically different, yet similar each species can be from one another.

Sprengel’s Sedge (Carex sprengelii) in fruit

A good friend and botanical mentor of mine once said that sedges are the “botanical caviar” of the plant world and I don’t disagree. It takes a special and dedicated mind to study and learn these potentially frustrating plants but it is a vital tool in any botanist’s utility belt. Almost any survey or botanical inventory of a site/habitat is going to have sedges, Carex most specifically, come out as the most numerous and diverse vascular plant representative.

Green Cotton-sedge (Eriophorum viridicarinatum) in fruit

As was mentioned earlier there are well over a dozen different genera of sedges in Ohio, outside just the true-sedges (Carex). The spike-rushes (Eleocharis), bulrushes (Scirpus), umbrella-sedges (Cyperus), beak-sedges (Rhynchospora) and cotton-sedges (Eriophorum) are just a sampling of our other genera. Don’t let the use of ‘rush’ in some of the common names fool you, they are genuine sedges. Why the use of a plant’s scientific or Latin name is superior, especially when dealing with sedges.

Different achenes of Ohio’s Nut-rushes (Scleria)

One of the most fascinating aspects of sedges is the miniscule yet intricate detail many species’ achenes exhibit. These tiny seeds, often not much larger than a pinhead have some of the most impressive patterns and designs in the natural world. None dazzle more than the mature achenes of the nut-rushes (Scleria spp.). Ohio is home to four different taxa and each one can best be told apart by their seed’s unique architecture. The photo above is one I put together a couple years ago under heavy magnification. The achene of the top right species, S. verticillata is little more than a millimeter wide. If those little seeds don’t impress, I don’t know what else would!

Line up of different Carex sedges from a fen meadow in Ownes Fen SNP

At the end of the day most people would be satisfied to know a sedge is a sedge when they see one and that’s a perfectly fine place to stop. Recognizing their existence and differences is better than ignoring them all together. Hopefully this post has shed some better light on a vastly underappreciated group and supplied a new appreciation for them. Or perhaps this was your first formal introduction to them. If anything I wish for my readers to walk away admitting sedges are more attractive and interesting than previously thought. I don’t expect many to be bitten by the sedge bug and become a fellow sedge-head but you never know and you’re always welcome aboard! Remember: sedges are plants too!

Thanks for reading and hope you’re having a wonderful summer field season. Get outside and enjoy our fine state nature preserves and the wealth of plants and wildlife within. I’ll see you out there and happy botanizing!

Andrew Gibson