Sedge Grass (Carex)

Sedge grass, also known as Carex, is a diverse group of plants that look like grasses, but are actually perennials. They grow in tufts of strappy leaves that usually stay evergreen in mild climates. Sedges come in a wide range of colors, including chartreuse, copper, bronze, yellow, blue and lime green. They are highly adaptable and are often used to fill large spaces, either as groundcovers or as alternatives to lawns.

I. Appearance and Characteristics 

Carex is a vast genus of over 2,000 species of grass-like plants in the family Cyperaceae, commonly known as sedges (or seg, in older books). Other members of the family Cyperaceae are also called sedges, however those of genus Carex may be called true sedges, and it is the most species-rich genus in the family. The study of Carex is known as caricology.

All species of Carex are perennial, although some species, such as C. bebbii and C. viridula can fruit in their first year of growth, and may not survive longer. They typically have rhizomes, stolons or short rootstocks, but some species grow in tufts (caespitose). The culm – the flower-bearing stalk – is unbranched and usually erect. It is usually distinctly triangular in section.

The leaves of Carex comprise a blade, which extends away from the stalk, and a sheath, which encloses part of the stalk. The blade is normally long and flat, but may be folded, enrolled, channeled or absent. The leaves have parallel veins and a distinct midrib. Where the blade meets the culm there is a structure called the ligule. The color of foliage may be green, red or brown, and “ranges from fine and hair-like, sometimes with curled tips, to quite broad with a noticeable midrib and sometimes razor sharp edges”.

The flowers of Carex are small and are combined into spikes, which are themselves combined into a larger inflorescence. The spike typically contains many flowers, but can hold as few as one in some species. Almost all Carex species are monoecious; each flower is either male (staminate) or female (pistillate). A few species are dioecious. Sedges exhibit diverse arrangements of male and female flowers. Often, the lower spikes are entirely pistillate and upper spikes staminate, with one or more spikes in between having pistillate flowers near the base and staminate flowers near the tip. In other species, all spikes are similar. In that case, they may have male flowers above and female flowers below (androgynous) or female flowers above and male flowers below (gynecandrous). In relatively few species, the arrangement of flowers is irregular.

The defining structure of the genus Carex is the bottle-shaped bract surrounding each female flower. This structure is called the perigynium or utricle, a modified prophyll. It is typically extended into a “rostrum” or beak, which is often divided at the tip (bifid) into two teeth. The shape, venation, and vestiture (hairs) of the perigynium are important structures for distinguishing Carex species.

The fruit of Carex is a dry, one-seeded indehiscent achene or nut which grows within the perigynium. Perigynium features aid in fruit dispersal.

Carex species are found across most of the world, albeit with few species in tropical lowlands, and relatively few in sub-Saharan Africa. Most (but not all) sedges are found in wetlands – such as marshes, calcareous fens, bogs and other peatlands, pond and stream banks, riparian zones, and even ditches. They are one of the dominant plant groups in arctic and alpine tundra, and in wetland habitats with a water depth of up to 50 cm (20 in).

II. How to Grow and Care

Sunlight

There is a sedge for every light condition. Although few of them are fond of full shade, some species, such as Appalachian sedge, will grow nicely in the shade garden. Blue sedges tend to prefer full sun conditions and will do best in warmer climates.

Most species are amenable to partial shade conditions. The ideal situation for nearly every species is part shade or filtered sunlight. Here, they will grow lush and full, spreading to their full potential.

Temperature and Humidity

When it comes to temperature, many varieties are cool-weather-loving. Japanese sedge, for example, does its best growing under 75°F (24°C). Like most other factors that influence growth, these plants are very tolerant of a wide range of temperatures, though. They are also not concerned with humidity and can tolerate high or low levels.

Watering

There are a handful of sedges that are drought tolerant once established. Pennsylvania sedge and species native to New Zealand are the most drought-tolerant. Most of these plants prefer moisture, though. Cool, moist soil is ideal for the majority of species.

If you have a moisture-loving sedge, make sure to keep the soil moist. This is important during the hot summer months. Regular rainfall should be sufficient in most climates. In times of prolonged drought, most species will need weekly watering. Some species are even tolerant of standing water or wet soil.

Soil

Most types of sedge prefer a similar type of soil. Fertile, well-drained soil that holds moisture is the ideal environment for the majority of species. The exceptions are a handful of species that prefer very wet or dry soil types.

The most common species that thrive in a boggy environment is C. oshimensis. This is a great plant for anyone with drainage issues in the garden. It will be happy growing at the edge of a pond, too. Conversely, C. flacca and C. flaccosperma are both dry-weather species. They are among the more drought-tolerant.

In terms of soil pH, this is a versatile group of plants. The healthy range for sedge is in the neighborhood of 5.5-7.5. They are well adapted to tolerate soil that is neutral, slightly acidic, or slightly alkaline.

Fertilizing

Sedges are not heavy feeders, so fertilizing may not be necessary at all depending on your soil. If you work in some organic compost and have naturally rich soil, you’ll never need to worry about feeding your plants.

If you have poor soil and feel like your plants need a little boost, once yearly should do it. A light application of balanced liquid fertilizer, such as a 10-10-10 formula, will work perfectly. Don’t overdo the fertilizer because your sedges will suffer. Dilute if you’re unsure.

Planting Instructions

Because of the wide range of species, different types of sedges are best planted at different times of the year. Determining which one is native to an environment like yours is the best way to make this determination.

Sedges that prefer cool weather are best planted in the fall. Warm weather sedges tolerate planting in the fall or spring. There are a few species, the most common being Leatherleaf, that is best planted in spring.

If you are planting nursery starts, dig a hole that is about six inches wider than the root ball of the plant. The same applies to seedlings you have germinated. The root ball should be slightly visible above the surface of the surrounding earth. It’s also perfectly fine to direct sow your seeds in the garden.

Pruning

Propagation

The most common propagation method once you have this plant established is by division. You can also propagate them by seeds, but the germination rate does tend to be unpredictable.

Division

To divide your sedge plants, wait until early spring, just as they begin active growth. Dig up a clump of the plant, choosing one that is dense and healthy. The rest is simple; just use a knife or other tool to divide the root ball and foliage into smaller sections. Then re-plant them in whatever space you choose! You will know that your divisions are successful when you see new growth. This method is usually quite effective.

Seeds

If you have plants, let them go to seed. Then, remove the seeds and allow them to dry out in a paper bag over the winter. Otherwise, seeds are not hard to find, and you can purchase them in nurseries and online. Most of the cool weather species require cold stratification. Either plant your seeds in the fall or place them in the refrigerator for 90 days before planting. This will significantly improve the germination rate.

When starting your seeds, use a high-quality potting or starter mix that will retain moisture. These seeds need to stay moist during germination. Place your seeds on the potting mix and lightly press them into the soil. They will benefit from some light during germination. If you are directly sowing your seeds, keep this in mind. Plant seeds 12″ apart in the garden in groups of two or three. Thin them out once you can distinguish between seedlings.

Pests and Diseases

The most prevalent disease issues for sedge are root and crown rot. Both of these are the result of too much moisture. Since this is a moisture-loving plant, fungal issues commonly crop up. The best way to avoid fungal diseases is with drainage. For all but those species that like soggy soil, make sure that your beds have proper drainage.

You may see some other fungal issues, including rust. Treat these with a copper-based antifungal, and make sure your plants have proper air circulation. In terms of insects, aphids may come around occasionally but won’t usually kill the plant. Because of the moist soil, fungus gnats can also be an issue but pose no large threats to the plants.

Maintenance

During the growing season, there is little to do in terms of maintenance. You can deadhead the flowers if you prefer the way it looks, but pruning will not be necessary. Trim things up in the spring as your plants begin to grow again after dormancy. Cut back dead or diseased foliage and anything that is otherwise damaged.

The other important thing to check for at this time is rotting roots. Root rot is common because of the moisture the plant prefers. It’s not always deadly, though, as long as you remove the rotten portions. Check the center of the plant for any rotting, and remove any part of the plant and roots affected.

III. Uses and Benefits 

• Ornamental uses

Carex species and cultivars are popular in horticulture, particularly in shady positions. Native species are used in wildland habitat restoration projects, natural landscaping, and in sustainable landscaping as drought-tolerant grass replacements for lawns and garden meadows. Some require damp or wet conditions, others are relatively drought-tolerant. Propagation is by seed or division in spring.

The cultivars Carex elata ‘Aurea’ (Bowles’ golden sedge) and Carex oshimensis ‘Evergold’ have received the Royal Horticultural Society’s Award of Garden Merit.

• Other uses

A mix of dried specimens of several species of Carex (including Carex vesicaria) have a history of being used as thermal insulation in footwear (such as nutukas used by Sámi people). Sennegrass is one of the names for such mixes. During the first human expedition to the South Pole in 1911, such a mix was used in skaller, when camps had been set (after each stretch of travelling had been completed).

Carsten Borchgrevink of the British Antarctic Expedition 1898-1900 reported “I found the Lapps method of never using socks in their Finn boots answered well. Socks are never used in Finnmarken in winter time, but ‘senne grass’ which they, of course, had a special method of arranging in the ‘komager’ (Finn boots) … if you get wet feet while wearing the grass in the ‘komager’ you will be warmer than ever, as the fresh grass will, by the moisture and the heat of your feet, in a way start to burn or produce its own heat by spontaneous combustion.

The great thing seems to be to arrange the grass properly in the boots, and although we all tried to imitate the Finns in their skill at this work, none of us felt as warm on our feet as when they had helped us.”

Species serve as a food source for numerous animals, and some are used as a livestock hay.

• Use by Native Americans

The Blackfoot put carex in moccasins to protect the feet during winter. The Cherokee use an infusion of the leaf to “check bowels”. The Ohlone use the roots of many species for basketry. The Goshute use the root as medicine. The Jemez consider the plant sacred and use it in the kiva. The Klamath people weave the leaves into mats, use the juice of the pith as a beverage, eat the fresh stems for food and use the tuberous base of the stem for food.

The indigenous people of Mendocino County, California use the rootstocks to make baskets and rope. The indigenous people of Montana also weave the leaves into mats and use the young stems as food. The Navajo of Kayenta, Arizona grind the seeds into mush and eat them. The Oregon Paiute weave it to make spoons. The Pomo use the roots to make baskets, and use it to tend fishing traps.

They also use it to make torches. The Coast Salish use the leaves to make baskets and twine. The Songhees eat the leaves to induce abortions. The Nlaka’pamux used the leaves as brushes for cleaning things and use the leaves as forage for their livestock. The Wailaki weave the roots and leaves into baskets and use the leaves to weave mats. The Yuki people use the large roots to make baskets.