We’ve had a very wet summer. More rain than we’ve seen in years has fallen periodically an inch or two at a time–including those weeks when we’ve been away on vacation. The result is that the yard has remained green and lush all summer, and places normally dry are a bit soggy. The peppers have thrived in our little garden patch, and so have the grasses and weeds.
I start weeding and come across a pretty grassy plant with a triangular stem and feathery green displays at the top of the stem. It turns out to be a sedge called strawcolored flatsedge (Cyperus strigosus).
So it’s a sedge, not a grass at all. That raises the question for me, as to what is a sedge anyway? I’ve confused sedge with sage, and now I realize they are not the same. In fact, not counting the sage, I’ve conflated three types of plants, considering them all grasses–sedges, rushes and grasses. Let’s take a look at them.
These plants, known as graminoids, all have some things in common. They grow on long stems known as culms with long thin blade-like leaves. They produce seeds but also spread through their root systems. They have evolved to coexist with grazing animals like cattle and bison.
Generally speaking, it’s relatively easy to tell these three types of plants apart. A common rhyme goes like this: “Sedges have edges; rushes are round; grasses have nodes from the top to the ground.”
Sedges have edges refers to the fact that the stems of sedges are triangular. So if you roll the stem of a sedge between your fingers, you will feel the edges of the triangle that forms the stem. In addition, sedges have leaves growing out of all three sides of the stem. The stems (officially called culms), are solid, not hollow like grasses. They’re filled with a pithy center. Sedges also have carrot-like roots which give them an advantage in poor soils.
Papyrus is a kind of sedge that the Egyptians made writing scrolls out of. Other sedges are named grasses such as cottongrass, sawgrass and nutgrass, but are technically sedges.
Rushes are round. The stems of rushes are definitely round and solid. They are smooth to the touch, and don’t have any nodes on them. Traditional uses of rushes include tying, thatching and binding as well as weaving mats, chair seats and baskets. Rushes were used as a floor covering in the Middle Ages. They were probably woven into mats. The pith from a rush’s stem could be used as a primitive candle.
Grasses have nodes from the top to the ground. Grasses are everywhere on Owl Acres, taking several forms. They all have nodes on their stems, and they all have leaves growing at the nodes. The stems are also hollow, often filled with juice. Sugarcane is a grass; so is foxtail, bamboo, and Kentucky bluegrass.
Our strawcolored flatsedge is not strawcolored. At this point anyway, it’s all very green. It’s not flat either. It’s about three and a half feet tall with a triangular stem or culm. It has long thin leaves that grow from the bottom part of the culm. Each leaf has two prominent veins on the top side and one prominent vein on the bottom. At the top of the stem collections of little green feathery spikes grow on rather long stems. These are the flowers. They are wind-pollinated so don’t have to waste time and energy attracting pollinators. They just wave their feathery tops in the wind, catch the pollen they need, and go on to make one seed for every little green spiky. floret. As the “flowers” mature, they do become straw-colored. The seeds are encased in elongated, dry, three-sided fruits. I’m not sure why it’s called flatsedge. None of it seems to be flat.
Strawcolored flatsedge is native to North America. It is a perennial, and prefers to grow in marshes, bogs, ditches and other wet places. So what was it doing in my yard?
Once established, it can expand through its root system into large colonies. It also disperses seeds to aid in its quest to conquer new lands.
Strawcolored flatsedge has fit itself into the Iowa ecosystem. It hosts a variety of insects including the flatsedge borer moth, (Diploschizia impigritella) which bores into the bottom of the stem. The larvae of the sedge gall midge (Planetella caudata), the yellow sugar cane aphid (Sipha flava), the viburnum-sedge aphid (Ceruraphis eriophori), and the blissid bug, Ischnodemus rufipes also feed on flatsedges. Birds and small mammals like mice eat the nutty fruits of the plant.
A bit of much-needed weeding and trimming vanquished our strawcolored flatsedge. I guess it qualified as a weed. Interesting though. It was happy to be growing in a place which was not normally wet but was this year because of all the rain.
Photo by Author. Not strawcolor, but green. Not flat, but triangular. Not grass, but Sedge. Strawcolor Flatsedge displays a tangle of long slender leaves and bristly flower/seed stalks in the margin of the yard next to the sidewalk.