Cyperus rotundus (coco-grass, Java grass, nut grass, purple nut sedge, red nut sedge, Khmer kravanh chruk) is a species of sedge (Cyperaceae) native to Africa, southern and central Europe (north to France and Austria), and southern Asia. The word cyperus derives from the Greek "κύπερος" (kuperos) and rotundus is from Latin, meaning "round". The earliest attested form of the word cyperus is the Mycenaean Greek ku-pa-ro, written in Linear B syllabic script.
Cyperus rotundus is a perennial plant, that may reach a height of up to 140 cm (55 inches). The names "nut grass" and "nut sedge" (shared with the related species Cyperus esculentus) are derived from its tubers, that somewhat resemble nuts, although botanically they have nothing to do with nuts.
As in other Cyperaceae, the leaves sprout in ranks of three from the base of the plant, around 5–20 cm long. The flower stems have a triangular cross-section. The flower is bisexual and has three stamina and a three-stigma carpel, with the flower head have 3-8 unequal rays. The fruit is a three-angled achene.
The root system of a young plant initially forms white, fleshy rhizomes, up to 25 mm in dimension, in chains. Some rhizomes grow upward in the soil, then form a bulb-like structure from which new shoots and roots grow, and from the new roots, new rhizomes grow. Other rhizomes grow horizontally or downward, and form dark reddish-brown tubers or chains of tubers.
It prefers dry conditions, but will tolerate moist soils, it often grows in wastelands and in crop fields.
Invasive problems and eradication 
Cyperus rotundus is one of the most invasive weeds known, having spread out to a worldwide distribution in tropical and temperate regions. It has been called "the world's worst weed" as it is known as a weed in over 90 countries, and infests over 50 crops worldwide. In the United States it occurs from Florida north to New York and Minnesota and west to California and most of the states in between. In the uplands of Cambodia, it is described as an important agricultural weed.
Its existence in a field significantly reduces crop yield, both because it is a tough competitor for ground resources, and because it is allelopathic, the roots releasing substances harmful to other plants. Similarly, it also has a bad effect on ornamental gardening. The difficulty to control it is a result of its intensive system of underground tubers, and its resistance to most herbicides. It is also one of the few weeds that cannot be stopped with plastic mulch.
Weed pulling in gardens usually results in breakage of roots, leaving tubers in the ground from which new plants emerge quickly. Ploughing distributes the tubers in the field, worsening the infestation; even if the plough cuts up the tubers to pieces, new plants can still grow from them. In addition, the tubers can survive harsh conditions, further contributing to the difficulty to eradicate the plant. Hoeing in traditional agriculture of South East Asia does not remove the plant but leads to rapid regrowth.
Most herbicides may kill the plant's leaves, but most have no effect on the root system and the tubers. Glyphosate will kill some of the tubers (along with most other plants) and repeated application can be successful. Halosulfuron-methyl (chemical name: Methyl 5-[((4,6-dimethoxy-2pyrimidinyl)amino)carbonylaminosulfonyl]-3-chloro-1-methyl-1H-pyrazole-4-carboxylate), brand name "Manage" (now renamed "SedgeHammer" in the USA) or "Sempra" in Australia, will control nut grass after repeated applications without damaging lawns.. In Cambodia the plant does not tolerate shading, while 2,4-D (2,4-Dichlorophenoxyacetic acid slows growth in pastures and mulch crops.
Uses and positive aspects 
Despite its bad reputation, Cyperus rotundus has several beneficial uses.
Folk medicine 
The plant is used in popular medicine:
- In traditional Chinese medicine it is considered the primary qi regulating herb.
- The plant is mentioned in the ancient Indian ayurvedic medicine Charaka Samhita (ca. 100 CE). Modern ayurvedic medicine uses the plant, known as musta or musta moola churna, for treating fevers, digestive system disorders, dysmenorrhea and other maladies.
- Arabs of the Levant traditionally use roasted tubers, while they are still hot, or hot ashes from burned tubers, to treat wounds, bruises, carbuncles, etc. Western and Islamic herbalists including Dioscorides, Galen, Serapion, Paulus Aegineta, Avicenna, Rhazes, and Charles Alston have described medical uses as stomachic, emmenagogue, deobstruent and in emollient plasters.
Modern uses and studies 
Modern alternative medicine recommends using the plant to treat nausea, fever and inflammation; for pain reduction; for muscle relaxation and many other disorders.
Several pharmacologically active substances have been identified in Cyperus rotundus: α-cyperone, β-selinene, cyperene, patchoulenone, sugeonol, kobusone, and isokobusone, that may scientifically explain the folk- and alternative-medicine uses. A sesquiterpene, rotundone, so called because it was originally extracted from the tuber of this plant, is responsible for the spicy aroma of black pepper and the peppery taste of certain Australian Shiraz wines.
Sleeping mats 
The well dried coco grass are used as mats for sleeping.
- "Germplasm Resources Information Network: Cyperus rotundus".
- MARTIN, Robert & POL Chanthy, 2009, Weeds of Upland Cambodia, ACIAR Monagraph 141, Canberra, 
- κύπερος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
- rotundus, Charlton T. Lewis, Charles Short, A Latin Dictionary, on Perseus Digital Library
- Palaeolexicon, Word study tool of ancient languages
- Holm et al., LeRoy G.; Plucknett, Donald L.. (1977). The World's worst weeds: Distribution and biology. Hawaii: University Press of Hawaii.
- USDOE-Bonneville Power Administration, Halosulfron-methyl Herbicide Fact Sheet, March 2000
- "Effect of polyherbal formulation on experimental models of inflammatory bowel diseases". J Ethnopharmacol 90 (2-3): 195–204. February 2004. doi:10.1016/j.jep.2003.09.042. PMID 15013181.
- Manish V. Patel et al. (2010-10). "Effects of Ayurvedic treatment on forty-three patients of ulcerative colitis". Ayu. 31 (4): 478–481. doi:10.4103/0974-8520.82046. PMC 3202252. PMID 22048543.
- Aegineta Paulus (translation and commentary by Francis Adams) (1847). The seven books of Paulus Aegineta: Translated from the Greek.
- Charles Alston (1770). Lectures on the materia medica: containing the natural history of drugs.
- Determination of Rotundone, the Pepper Aroma Impact Compound, in Grapes and Wine. Tracey E. Siebert, Claudia Wood, Gordon M. Elsey and Alan P. Pollnitz. J. Agric. Food Chem., 2008, 56 (10), pp 3745–3748. URL: http://pubs.acs.org/doi/abs/10.1021/jf800184t. Accessed 9/10/2012.
|Wikimedia Commons has media related to: Cyperus rotundus|
- Flora Europaea: Cyperus rotundus
- USDA Plants Profile: Cyperus rotundus
- USDA Natural Resources Conservation Service: Cyperus rotundus (pdf file)
- Use in Chinese and Ayurvedic medicine
- A Tel-Aviv University study mentioning its nutritional importance for migrating birds (in Hebrew)
- Caldecott, Todd (2006). Ayurveda: The Divine Science of Life. Elsevier/Mosby. ISBN 0-7234-3410-7. Contains a detailed monograph on Cyperus rotundus (Musta; Mustaka) as well as a discussion of health benefits and usage in clinical practice. Available online at http://www.toddcaldecott.com/index.php/herbs/learning-herbs/310-musta