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What is a Sedge?

What is a Sedge? | Copyright GreenPlantSwap Ltd

Sedges are a group of plants which form clumps, mounds, or tussocks: they have long, narrow leaves and are often evergreen. Some of them are merely ankle height, many of them are knee height, and some can even grow to waist height. They are particularly useful in situations with poor soil, as they are remarkably tough and establish themselves well, often being capable of spreading quite extensively.

Most Sedges will grow almost anywhere, but they particularly like damp soils, and indeed there are several Sedges which are perfect for waterlogged soil, and which can often provide dramatic water-side foliage.

Although technically they are flowering plants, the “flowers” are quite insignificant, so they are mostly grown just for their foliage: but those insignificant flowers produce large quantities of seeds, allowing these plants to spread widely, as well as extending their clumps from creeping underground rhizomes.

The botanical name for the true Sedge is Carex, and they are monocotyledons, which means that they are flowering plants whose embryonic seeds only have one cotyledon or leaf: most of what we think of as “flowering plants” are dicotyledons, with two of these seed-leaves. It's a tiny distinction, but extremely important as it is one of the most basic classifications.

In gardening terms, most monocotyledons have long, thin, strap-like leaves in which the veins run parallel to the long sides, instead of the familiar branching net of veins which we see in the dicotyledons. Monocots include, in addition to Sedges, the similar-looking Grasses and Rushes, plants such as Lilies, Bamboo, and Onions, and many of our flowing bulbs such as Tulips, Daffodils, and Iris.

What are Sedges used for?
The 34 species of Carex in our Plant Finder include something for everyone, from glossy green leaves through stripy variegated foliage, right into foliage of bronze and red: and the leaves themselves are everything from the wide, soft leaves of Carex elata (Bowles' golden sedge), through the broad, tough, centrally-ridged leaves of Carex siderosticha (the rather unimaginatively-titled Broad-leaved sedge), to the narrow hard hair-like leaves of Carex buchananii (Leatherleaf sedge). They are deservedly popular with horticulturalists as many of them will grow happily in shade, filling awkward corners and acting as ground cover to prevent the establishment of unwanted weeds: and despite looking like grass, they are rarely troubled by browsing deer or bunnies.

These properties make them very useful for erosion control, on hillsides as well as in waterside areas.

They are perennial plants, so they come back year after year, and many of them are evergreen, although a lot of the bronze-foliaged types can turn a less-attractive brown colour in a mild, damp winter: a cold winter will keep them crisp and sharp looking, and they can look fabulous when rimmed with frost. They are very easy-care plants: if they start to look a little tatty in spring, all you have to do is shear off the old foliage and they will quickly re-grow with fresh new leaves.

One of the most frequent plantings in the UK is Carex pendula, aptly known as Pendulous sedge, whose fat, catkin-like flowers dangle at the end of long hard stalks in early summer. They establish themselves well in a damp or pond-side environment, but will seed themselves happily all through the garden – in fact, they seed so prolifically that this particular Sedge is now often found growing in the wild.

In contemporary gardening, Sedges are most often found situated in pots, where their foliage can spill gracefully over the sides, and can either provide an interesting backdrop to flowering plants, or indeed can be appreciated in their own right.

Historically, Sedge has been used as a weaving material in countries such as Korea: mats, baskets and decorative items are woven from bleached Sedge leaves and have been, in their time, highly prized items. Also, several different species of Sedge have been identified as being used in footwear, as an insulating layer: a testament to the fact that Sedges will grow as far north as Scandinavia.

The Sedge in popular culture

Sedges are strangely absent from modern culture, but 4,000 years ago, the Sedge was the symbol for Lower Egypt, while the bee stood for Upper Egypt: in modern times, however, its influence has been reduced to the name of a brand of handwash.

How do you know it's a Sedge?
When looking at a clump of something green and grass-like, you might be confused as to whether they are Sedges, Grasses or Rushes: it's a difficult group. The first rule is “Sedges have Edges”. The flowering stems are triangular in cross-section, so each one will have three distinct corners or edges, and if you cut one across, you can clearly see this. Alternatively, to avoid damaging the plant just to identify it, you can try to roll a stem between your finger and thumb: if it won't roll easily, then it is a Sedge.

There is a simple mnemonic which is useful when looking at “things that look like grass” and it goes like this:

Sedges Have Edges,
Rushes are Round:
Grasses are hollow,
So which have you found?

Like all mnemonics, nothing is ever quite that simple, but it is a very good place to start!

There are not many plants called Sedge that are not proper Carex: one notable one is Uncinia or Red Hook Sedge, a low-growing plant which has amazingly red foliage all year round.

There is also the similar-sounding but utterly different-looking Ursinia: they are half-hardy plants with pinnate, fern-like foliage and bright, daisy-like flowers and are commonly known as Hook Sedge or, more appropriately, Jewel of the veldt.

Acorus gramineus is known as Dwarf sedge (or Japanese rush, or Japanese sweet flag) and it has curved, rigid glossy green leaves, forming low clumps of foliage in wetlands and shallow water: it can spread aggressively, making it a good ground cover plant.

Less aggressive is Acorus calamus or Murtle sedge, which is commonly grown as an aquatic, or bog plant. The roots have been used in the past for perfume, medicinally and as a food, as substitutes for cinnamon, nutmeg and ginger: but today, it is better to be safe, and to buy your medicine and spices from approved sources, and to just appreciate this as a garden plant.

And finally, returning to Carex, we have the aptly-named Mace sedge (Carex grayi) whose flowers are quite uninteresting, but which forms intricate inflated seed-pods, which look just like miniature versions of those spiked balls which were spun, on a short length of chain, in medieval times. They look quite murderous, but luckily they are only 1” (2.5cm) across!

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