Although similar to grasses, sedges have quite different flower structures. Sedges have evolved into a fantastic variety of species. Sedges can be found from the tops of mountains to the lowest seashores. Most people won’t even notice them when walking around.
Sedges are distinct from rushes and grasses. They are grass-like plants with small flowers and triangular stems. They can be found growing in wet ground. Sedges can be found growing in temperate and cold regions. There are over 4,000 species of sedge in the world.
Sedges, rushes, and grasses are three different plants, although they are not easy to tell apart when walking past them. All three families are green herbaceous plants with reduced, wind-pollinated flowers. Out of the three families, rushes are the most distinct as they have six petal-like structures called the perianth segments.
Sedges and grasses are more complex and have an arrangement of floral organs, and are different from conventional flowers. Grass flowers have both sexes present, whereas sedges have distinct male and female flowers.
Sedges and grasses also have different arrangements of their leaves and the shapes of their stalks. From above, grass leaves are organized in two ranks on a cylindrical system. However, Sedges have leaves arranged in three ranks around the stem. The stem is generally triangular when viewed as a cross-section.
The flowers on the sedge are little more than reproductive organs and a subtending scale called the glume. The flowers are gathered into cylindrical heads called spikes.
Sedges are plants in the genus Carex that make up the majority of species in the family Cyperaceae. There are about 4,000 species in the family Cyperaceae.
Three groups of sedge
There are three groups, and they can be divided according to the structure of the spikes and the male and female flowers. The first group consists of plants where the spikes all look similar, regardless of whether they bear male, female, or mixed flowers. If male and female flowers are combined, each flower is borne at opposite ends of the spike.
The second group of sedges only bear either male or female flowers. These can be distinguished by their look, as male spikes look different from females.
The third group only bears a spike and no flower.
With over 4,000 species of sedge, it would be not easy to go through them all here. I will start with the sand sedge, a widespread species in Europe and Asia. Sand sedge is a member of the first group, bearing spikes that look alike. Towards the top of the plant, the spikes are single-sexed, while the ones nearer the bases bear flowers of both sexes. The spikes are closely set together.
Sand sedges can be found in fixed dunes and sand and spread over a wide habitat area. They spread using underground rhizomes that grow through the sand.
Another sedge is called spiked sedge. They have several short spikes which are gathered into a head. The spiked sedge appears more densely tufted as they have short rhizomes or underground stems which put up shoots. Sand sedge puts up solitary shoots every few inches.
Like the spiked sedge, only in it is densely tufted; the remote sedge has spikes that are widely spaced along the upper half of the stem. This makes it very different from the sand and spiked sedges. The spikes do not overlap, although those at the top are closer together. The spikes carry longer bracts at the base of the plant than at the top. Remote sedges can be found around damp, shaded places, preferably with acidic soil.
The second group of sedges includes the pendulous sedge, which can often be found in gardens. They are large with clumps up to 70cm across with a stem of 6 feet tall. The spikes are larger and carry one or two male spikes and four or five female spikes. The male spikes are about 6-10cm long and can be found at the top of the stem, while the female spikes are longer and can measure up to 16cm long. Female spikes can be identified as upright, although they do droop as they get older.
The greater pond sedge can grow up to 4ft tall and can be found at the side of slow-moving rivers, ponds, and ditches. It is usually immersed in the water at the base. The flower spikes typically consist of one male at the top, and the lower spikes are female. The spikes are plump when compared to other species of sedge.
Sedge can also be found on hillsides and hedgebanks. The hairy sedge is a member of the second group and is, as its name suggests, hairy. They can be found in areas with high rainfall.
Two other species found on hillsides are the common sedge and the glaucous sedge. The common sedge is widespread and prefers areas of watersides and wet grass. The one membranous bract surrounding the spike is purple to black with a pale line down the middle. The leaves have a bluish tinge and fruit of purple or green.
It may be a glaucous sedge if the sedge has a bluish tinge to its leaves. The upper surface is green. They are often confused with the common sedge, although one way to tell them apart is to look at the ovary of the female flowers. There are three ovaries on the glaucous sedge, but there are only two on the common sedge.
The third group contains just a single spike. The flea sedge is the most common and can be found in chalk or limestone areas with damp grassland. At the top, the male spikes are narrow, while on the bottom, the female flower drops early, spreading outwards and downwards. It gets its name from this, as it looks like a flea.