The Forest in June: Graminoids
One may not know it, but some of those grassy-looking plants we come across in the forest and in the field aren’t grasses at all! We all know the typical image of a graminoid (that is, a grassy-looking plant): long stem and long, thin leaves, with a head of inconspicuous atypical flowers that become a dense cluster of seeds. Graminoids are, however, composed of three distinct groups, which can occupy different niches.
The first group are the sedges, a group that contains approximately 5,500 known species, across the globe. Cyperaceae, or the sedge family, contains the papyrus sedge (Cyperus papyrus) and the water chestnut (Eleocharis dulcis), as well as several common lawn weeds. Sedges are commonly characterized by their triangular-shaped cross-section (with some exceptions), and they have grassy-looking long, flat leaves that commonly grow from the ground (known as “basal” leaves) or in whorls of three. This triangular base can be felt for easy identification. Sedges can be found in a multitude of environments, but many are adapted to wetlands or poor soil conditions. Much like grasses, there are ecosystems dominated by sedges, known as “sedgelands”. Their seed heads vary from a tightly dense ball to a loose spray.
The second group is the rushes, which are the relatively small family Juncaceae. The Juncaceae are composed of only 464 species, but are also widely dispersed. Rushes can be identified by their round stems and round basal leaves, with several exceptions, and commercially are not used for many things other than decorative perennials and the weaving of classic Japanese tatami mats. Rushes are adapted to wet environmental conditions, so look for them in areas prone to flooding and poor drainage. Their seeds are usually contained within capsules on a nondescript small head.
The third group is, of course, the grasses, which provide us with our grains as well as sugar cane and bamboo. Grasses belong to the family Poaceae and contain a whopping 12,000 species, making the Poaceae the fifth largest plant family in existence. They can be identified by having an alternate arrangement of flat leaves that sheath the main stem, which grow from nodes, or junctures of the stem. They are extremely diverse, widespread, and comprise many ecosystems of grasslands and savannahs.
These three families are greatly responsible for protecting fertile lands against erosion, creating deeper and more fertile soils, creating habitat and food for many animals (and thus increasing the availability of nutrients for the entire ecosystem), and with some rushes, even fixing airborne nitrogen in nutrient-poor soils. Colloquially, plants of each group can be separated according to the following saying:
“Sedges have edges,
Rushes are round,
Grasses are hollow,
So what have you found?”
By looking at the shape and placement of the leaves, the shape of the stem, and its cross-section, we can all likely identify a sedge, a rush or a grass. This June, we can see grasses, rushes and sedges in Black Rock Forest at their peak, and watch as they slowly begin to form into seeds.