Sometimes the simple questions lead us to the most interesting answers. At a holiday dinner this year one of our relatives asked us what the actual botanical definition of a “grass” was. We had a good answer, but not a full one. In finding a more complete answer about what grass is, we learned a little more about grasses, rushes, and sedges, what they are, and how to tell them apart. Since innumerable species of these plants appear around the world and are often used in gardens and landscaping, we thought we’d tell you a bit about what we learned. So, join us as we dig in to a surprisingly interesting topic!
In several sources we read whilst learning about grasses, sedges, and rushes, we encountered a brief poem written to help folks learn to tell them apart:
Sedges have edges,
Rushes are round,
And grasses have knees
from the top to the ground.
Obviously we’ll go into a little more detail so you know what we’re referring to, but keep this bit of verse in mind as a memory aid if it helps you to do so.
Sedges have edges: While the name may be applied colloquially to many species, all true sedges are members of the family Cyperaceae and the genus Carex. Found throughout most of the world, sedges typically grow in clumps from a rhizome or stolon, putting out long grass-like leaves with a distinct triangular cross-section, giving them their distinctive “edges”. Various sedge species may be used traditionally in basket weaving, clothing, or dried and used as fuel for fires. Some species are edible or medicinal, but we know less about that and won’t share that information here. Some are used ornamentally to provide easy-to-maintain vertical interest in a garden bed or landscaping, with Japanese sedge (Carex oshimensis) and tufted sedge (Carex elata) being especially popular. There’s a sedge for every location: many are water loving but some prefer dry conditions and are drought tolerant so there’s likely a sedge for your landscaping or gardening application.
Rushes are round: Common in wetlands around the world, true rushes are members of the Juncaceae family. As our poem implies, rushes have round stems filled with a pithy white center. Leaves are typically alternate, growing “wrapped around” the stem at the base of the leaf. Rushes are less commonly used as ornamental landscaping than grasses or sedges, although some species appear in that role. Traditionally used to make cordage, rope, twine, fishing lines, baskets, or mats—Japanese tatami mats are traditionally made from a species of rush—these plants are now commonly used in rivers, lakes, and ponds to help stabilize the banks and in retaining ponds as a natural means of filtering waste out of water.
And grasses have knees/from the top to the ground: And now finally we address the plant that started this whole article. True grasses have hollow stems marked by “knees” or nodes that divide their hollow stem into sections and provide some strength and support. Species of grasses are found in nearly every part of the Earth, and include some of our most important edible and landscaping plants. Many important grains, including wheat, oats, and barley, are grasses. Sugarcane is a grass, as is bamboo. The uses and importance of grass are endless, but we’ll concentrate on where gardeners are likely to find them. Grasses are commonly used as ground cover in the form of lawn grass; popular species include Bermuda grass, bluegrass, St. Augustine grass, and ryegrass. We’ve written before about lawn care, but it’s fascinating to consider the rich botanical history and science behind the simple grass beneath our feet.
During a couple of long outside walks during the chilly holiday weather, we were able to identify a number of different rushes, grasses, and sedges in a typical suburban neighborhood. These plants are all around us, and knowing a bit more about them—including how to tell them apart—makes our interactions with the natural world just a bit more interesting. We hope you learned a little from this article, and if you’re using interesting species of sedge, grass, or rush in your garden we’d love to hear from you about it!
Leave a comment