What are Cyperaceae?
The Cyperaceae (sedges) form one of the larger and more diverse plant families being actively researched at the Royal Botanic Gardens, Kew, comprising c. 4,000-5,000 species in 102-123 genera.
Sedges have a superficial resemblance to grasses. However, they are not closely related and differ in many characteristics, particularly in the structure of the inflorescence.
Sedges have considerable economic and ecological importance. They are, however, well-known for being difficult plants to identify and specialist advice is often required.
The Royal Botanic Gardens, Kew has a long-standing tradition of expertise in sedges and, with the richness of its collections, is uniquely placed at the forefront of research on and identification of this family.
Importance of Cyperaceae
A number of sedges are serious and persistent weeds of agriculture, particularly in the tropics, where they are often associated with rice cultivation. One species, Cyperus rotundus, has the dubious reputation of being termed "the world's worst weed".
Several species are used as human food plants, the most notable of these being the edible tubers of Eleocharis dulcis (the chinese water chestnut, an important crop in Asia) and Cyperus esculentus (tiger nut or chufa). In many parts of the tropics, particularly Africa, sedges also provide fodder for domestic animals.
Some species, particularly papyrus (Cyperus papyrus), are becoming increasingly important for providing fuel in the tropics.
Sedges are being increasingly valued as horticultural subjects. Many species in cultivation show striking variegation of their leaves while others are highly regarded for their unusual floral structure. Many other species have potential horticultural uses.
The economic importance of sedges stretches back into antiquity with papyrus (Cyperus papyrus) being used for papermaking and boat building in ancient Egypt. Today, sedges are used throughout the tropics for basketry and mat weaving, and in parts of Africa and Asia they are cultivated for such purposes. They are also used for thatching, fencing, rope making, pot pourri and perfumery. Several species are recorded as having medicinal properties while others have the potential for use in erosion control and sand stabilization.
Sedges occur within a wide spectrum of vegetation types, ranging from the ground layer of tropical rainforest to temperate blanket bog and arctic tundra. They are important, often dominant elements of many wetland ecosystems, which today are severely threatened by the human activity. Indeed, some species may be in danger of extinction. Sedges are often highly sensitive to changes in nutrient status and their appearance or disappearance from a given area may act an indicator of damage to an ecosystem. They also provide food and shelter for wildlife. Therefore are of prime importance in conservation.
The Royal Botanic Gardens, Kew has maintained a long line of research on sedges going back over 100 years, and during this time an almost continuous succession of botanists have worked on the family. As a result the Kew herbarium has a collection of c.100,000 Cyperaceae specimens which is unrivalled elsewhere and continues to grow at some 2,000 to 3,000 specimens per year. The collection at Kew is particularly rich in type material and many sedge species were first described by Kew botanists.
Historically, the collection is particularly strong in specimens from Africa, India and Brazil, but there is a wide range of material from all parts of the world sedges are present. It is fair to say that nearly all the sedge species known to science are represented by specimens in the herbarium. About two-thirds of the specimens sent to us require naming and it is from this material that new species may be discovered.
In all sedge research at the Royal Botanic Gardens, Kew, particular importance is being attached to the structure of the fruits (variously termed nuts, nutlets or achenes). Surveys of these using scanning electron microscopy are yielding many useful characters. New techniques and sources of data, including DNA sequencing, are continually being looked at in order to improve the classification of sedges. Special emphasis is placed on cladistic and phenetic techniques to analyse data.
Research activities are divided into three main areas.
Monographic work is currently centred on the tribe Hypolytreae, a group of eight genera which occur mainly in the herb layer of tropical rainforest. Their inflorescence structure is unique in Cyperaceae but difficult to interpret due to its reduced nature. A better understanding of the tribe may hold important clues on the evolution of Cyperaceae. The genus Mapania has been revised and work is proceeding on Hypolytrum Attention is also being given to Scirpus s.l. and Cyperus. These occur worldwide and have considerable economic importance, but are rather poorly known. The work aims to clarify the limits and relationships of several sections within each genus and from this it is hoped to get a better understanding of the genera as a whole.
Floristic work currently covers East and Southern Africa, parts of Brazil, Thailand and Indo-China and Malaysia, with Flora accounts or checklists currently being prepared for these regions/countries.
Economic botany research includes the compilation of a database of Cyperaceae with economic and ethnobotanical importance. Nearly 400 taxa are now included, and a checklist is being prepared.
Bona fide researchers may examine the herbarium collections in person by prior arrangement. Specialist advice can be given on sedge classification.
A wide range of material covering a number of genera is in cultivation. Plants of both horticultural and scientific interest are represented and many are on display to the public.
The economic botany collections house a range of products and artefacts derived from sedges. The Survey of Economic Plants for Arid and Semi-Arid Lands (SEPASAL) details a number of sedges with actual and potential economic uses.
The seed bank has range of material in cold storage, and new accessions are continually being added. Material is available to research institutions on request.
The Library has the most comprehensive collection of books, papers and illustrations on sedges anywhere in the world, including some of the earliest literature published on the family.
Cyperaceae Newsletter published by the Royal Botanic Gardens, Kew and Gent University (Belgium) contains news of current research and short papers on sedges together with comprehensive lists of new names and bibliographies of newly published literature.