Coriandrum sativum (coriander)

Coriander (Coriandrum sativum) is a delicate culinary and medicinal herb belonging to the Apiaceae family. It is also widely grown for the fruits which are used as a spice. It is an erect, annual, glabrous, usually profusely branching herb, up to 1.3 m tall with a well-developed taproot. Its stem is solid, subterete, up to 2 cm in diameter. Coriander has its origin in the Near East. In all South-East Asian countries coriander is grown as a culinary herb and vegetable. Cropping for its fruits is restricted to higher altitudes. It is only known in cultivation; escapees from cultivation may become weeds. It is now a crop of both temperate and tropical regions and it is cultivated commercially in countries like India, Pakistan, Morocco, Romania, Russia, Bulgaria, France, Spain, Italy, the Netherlands, Myanmar, Turkey, Mexico, Canada, and Argentina and on a minor scale in the UK as well as in the USA. The largest grower and exporter of coriander fruits is India. The name coriander is thought to have been derived from the Greek word koris, which means bug, which is believed to have been used because the seeds apparently smell like bed bugs. It is known by several other names, including cilantro which is the Spanish word for coriander leaves, and these are much used in Mexican cuisine in North America. Owing to its flavouring properties, the herb is used in food preparations, perfumes and cosmetics, and it has a high economic value. It is also listed as a medicinal plant because of its ability to cure many diseases. The essential oils extracted from coriander have antibacterial, antioxidant, antidiabetic, anticancer and antimutagenic activities due to the presence of various chemical compounds.

Principal sources:  Ambrose et al. (2016); Ravindran (2017)

Coriandrum sativum is a culinary and medicinal herb which can become weedy outside cultivation. It is listed as “agricultural weed, casual alien, cultivation escape, garden thug, naturalised, sleeper weed, weed” in the Global Compendium of Weeds (Randall, 2012) and is listed as a weed in Israel, Lebanon, Morocco, and Taiwan (Holm et al., 1979). It is known to have escaped from cultivation in Puerto Rico, California (USA), and parts of the United Kingdom (Liogier and Martorell, 2000; Randall, 2012). The species spreads by seeds, which have been globally traded for both medicinal and food purposes since ancient Egyptian times. Considering that the species readily naturalises in introduced habitats (Forzza et al., 2010; Oviedo Prieto et al., 2012) as well as its long history of repeated introductions and known weediness, it can be regarded as potentially invasive, but is not currently recorded as an invasive species.

Often called the ‘carrot’ or ‘parsley’ family, the Apiaceae family consists of anise-scented, caulescent annual herbs from taproots characterized by flowers borne in rounded, compound umbels, from which the family’s earlier name of Umbelliferae is derived. The family includes many common vegetables and kitchen herbs such as celery, carrot, fennel, dill, coriander, and parsnip.

C. sativum, or coriander, is a commonly known kitchen herb. The genus name Coriandrum derives from the Greek ‘koriannon’, from ‘koris’ meaning ‘a bug’ or ‘bedbug’, referring to the pungent smell from the leaves and unripe fruits (Quattrocchi, 2012). The species name, ‘sativum’ is Latin for cultivated, as this species has been grown for culinary purposes since Egyptian times. In the past the species was also sometimes called ‘dizzycorn’ referring to its use in reducing dizziness by inhaling the aroma of crushed corriander seed (Loewenfeld and Back, 1978). The vernacular name 'cilantro', often used in the United States for coriander leaves, is also used for another species, Eryngiumfoetidum L., ‘sawtooth coriander’ (Diederichsen and Rugayah, 1999).

Coriander is a very variable species, and the botanical literature contains several subclassifications into subspecies, varieties and forms. Plant breeders and the seed trade often refer to two main groups of coriander based on fruit size: var. vulgare (large fruits) and var. microcarpum (small fruits. These groups also differ by other characters such as length of vegetation period, plant height, branching, vegetative productivity and leaf characters.

Recent investigations showed that the shape of the fruit is also important, and a third group (Indicum) with ovate fruits has been described. These three main groups also differ in content and composition of the essential oil of the fruit. A further distinction into nine ecogeographical types (European, North African, Caucasian, Central Asian, Syrian, Ethiopian, Indian, Bhutanic and Omanic) within the three groups is possible, which reflects very well the evolutionary pathway of the species. Chemotaxonomical investigations support such infraspecific classification. Diederichsen and Hammer (2003) proposed three subspecies covering ten botanical varieties of coriander, with characteristics of the volatile oil in the fruits being used together with morphological characteristics to describe the different groups.

Erect, annual, glabrous, usually profusely branching herb, up to 1.3 m tall with a well-developed taproot. Stem solid, subterete, up to 2 cm in diameter; older internodes sometimes becoming hollow, sulcate, mostly with a white bloom, light green with darker green ribs, occasionally violet. Leaves alternate, rather variable in shape, size and number, with a yellow-green, scariously margined sheath surrounding the supporting stem for up to three-quarters of its circumference; petiole and rachis subterete, sulcate, light green; blade white waxy, shiny green often with darker green veins; basal 1-3 leaves usually simple, withering early, often in a rosette, blade ovate in outline, deeply cleft or parted into usually 3 incised-dentate lobes; next leaves decompound, petiole 0-15 cm long, blade ovate or elliptical in outline, up to 30 cm x 15 cm, usually pinnately divided into 3-11 leaflets, each like the blade of the simple lower leaves or again pinnately divided into 3-7 simple leaf-like lobes; all higher leaves compound, petiole restricted to the sheath, blade divided into 3 leaflets of which the central one is largest, each often variously divided into ultimately sublinear, entire, acute lobes. Inflorescence an indeterminate, compound umbel; peduncle up to 15 cm long; bracts sublinear, 0-2, up to 11 mm long; primary rays 2-8, up to 4.5 cm long; bracteoles 0-6, linear, up to 1 cm long; secondary rays up to 20, up to 5 mm long; usually each umbellet has bisexual peripheral flowers, and the central flowers are sometimes male; calyx in all flowers represented by 5 small lobes; corolla with 5 white or pale pink petals, heart-shaped, very small (1 mm x 1 mm) in male flowers, in bisexual peripheral flowers usually 3 petals are larger: 1 petal develops 2 ovate lobes of about 3 mm x 2 mm and the 2 adjacent petals each develop one lobe; stamens 5, filaments up to 2.5 mm long, white; pistil rudimentary in male flowers, in bisexual flowers with inferior ovary, a conical stylopodium bearing 2 diverging styles up to 2 mm long, each one ending in a minutely papillate stigma. Fruit an ovoid to globose schizocarp, up to 5 mm in diameter, yellow-brown with 10 straight longitudinal ribs alternating with 10 wavy longitudinal ridges, often crowned by the dry persistent calyx lobes and the stylopodium with styles; fruit does usually not split at maturity; it contains 2 mericarps which each bear on their concave side 2 longitudinal, rather wide lines (vittae), containing essential oil. Seed 1 per mericarp, with testa attached to the fruit wall. Seedling with epigeal germination; taproot thin with many lateral roots; hypocotyl up to 2.5 cm long; cotyledons opposite, oblanceolate, up to 3 cm x 4 mm, pale green.

Coriander has its origin in the Near East. It is not known from the wild, but is widely cultivated, and escapees from cultivation may become weeds. It is now naturalized in many tropical and subtropical regions of the world.

In all South-East Asian countries coriander is grown as a culinary herb and vegetable. Cropping for its fruits is restricted to higher altitudes. In South-East Asia, as in many other parts of the world, coriander is usually grown as a small-scale horticultural crop. Large-scale production exists in southern Russia, the Ukraine and other East European countries.

C. sativum is one of the oldest spices in written history. It was cultivated by the Egyptians, Greeks, and Romans, included in medical remedies attributed to Hippocrates, and even used to describe the taste of manna in the Book of Exodus of the Bible; the oldest archaeological remains date to around 6000 BC in Israel (Diederichsen and Rugayah, 1999; Lawton, 2007; Floridata, 2015). The crop has since spread throughout the world, and different morphotypes have developed. Coriander reached South-East Asia from two directions: forms with ovoid fruits were introduced from India, while forms with small, globular fruits arrived later (after 400 AD) from China. Forms with large, globular fruits have only recently been introduced from Mediterranean or European countries.

The Romans reportedly introduced the species into Britain, where it came to be used for a wide range of culinary as well as medicinal and magical purposes; for example, in the Middle Ages, it was used to make love potions and to treat facial skin ailments (Phillips, 1822), and in British Victorian society its meaning in the language of flowers was ‘hidden merit’ (Lawton, 2007). It was present in France by the 17^th century, as the species was used as an ingredient in the famous Parisian liqueur of this time, eau-de-Carnes (Loewenfeld and Back, 1978). The species was apparently introduced to Austria for ‘fauna improvement’ and to Spain through horticulture (DAISIE, 2015). Today it is widely spread across Europe, and a common feature in various European culinary traditions.

Date of the species’ introduction to the West Indies is unknown, but it may have occurred during the early 19^th century. The species was not included in Macfadyen’s 1837 work on Jamaica, though he mentions the species’ seed as a means of comparative measure in other plant descriptions. Neither was the species included in Bello Espinosa’s work on Puerto Rico in the 1880’s, but it was listed by Britton (1918) in his flora of Bermuda, in which Britton writes that the species had been reportedly naturalised there by 1877, despite his failure to observe it growing there in 1918. The species was included in the Britton and Wilson (1923-1926) flora of Puerto Rico, in which the species was reportedly grown in gardens for culinary uses.

Risk of introduction for this species is low to moderate and warrants further research. In Cuba the species is listed as naturalized and is potentially invasive with a tendency to proliferate in any locality (Oviedo Prieto et al., 2012). The species has a long history of cultivation dating back to ancient Egyptian times, but it has been known to escape from cultivation and to naturalize beyond its native range, often becoming weedy (Liogier and Martorell, 2000; Randall, 2012). In addition to its long history of repeated introductions, other invasive traits include its fast growth rate, ability to produce seed that remains viable for more than a year, its ability to pioneer disturbed areas, and the global trade of its seed. Considering these factors, but also that the species has not yet been reported to be invasive anywhere in the world, risk of introduction for this species is low to moderate but more research is needed.

C. sativum is grown as a commercial crop and is also naturalized worldwide (Wiersema and León, 2013). It is a common cultivated plant in many parts of the world including Pakistan, where it is grown in the plains and hills (Flora of Pakistan, 2015). In Peru, the species occurs in disturbed areas of the Amazonian and Andean regions (Peru Checklist, 2015). In Missouri, USA the species is recorded as an uncommon plant found on roadsides, railroads, and open, disturbed areas (Flora of Missouri, 2015). It is a common garden plant in Puerto Rico (Liogier and Martorell, 2000).

Seedborne bacterial diseases can cause considerable losses, for example, Pseudomonas syringae pv. coriandricola. Heat treatment or chemical disinfection of fruits is possible. Fungal diseases (Fusarium sp., Ramularia sp.) can be avoided by treating the fruits with a fungicide before sowing. In India, fruit damage is reported to be caused by the chalcid fly, Systole albipennis. Pests like the biscuit beetle (Stegobium paniceum) may damage stored fruits.

The only information on organisms attacking C. sativum comes from cultivated crops. Seed-borne bacterial diseases can cause considerable losses, for example, Pseudomonas syringae pv. coriandricola. Heat treatment or chemical disinfection of fruits is possible. Fungal diseases (Fusarium sp., Ramularia sp.) can be avoided by treating the fruits with a fungicide before sowing. In India, fruit damage is reported to be caused by the chalcid fly Systolealbipennis. Pests like the biscuit beetle (Stegobiumpaniceum) may damage stored fruits.

This species has been reported to escape from cultivation and is known to be naturalized and weedy in some parts of the world (Randall, 2012), but there has been no research on the potential environmental or economic impacts of this species’ invasiveness to non-native habitats and no PIER risk assessment for this species has yet been conducted. Considering its centuries-long history of cultivation around the world and no current reports of its invasiveness, this species is not likely to become a high-threat species in the near future.

Coriander fruits are commonly used as a spice, being part of a large number of dishes. Ground coriander fruits are also an ingredient of spice mixtures like curry powder (containing up to 40% coriander). The leaves or the entire young plants are popular as a culinary herb and vegetable, for example, for chutneys or in soups. Taproots are also aromatic and are commonly used as a vegetable in China, Thailand and, to a lesser extent, in other South-East Asian countries. Green plants are dried for preservation and are traded on the world market as well as the fruits. Coriander is used in folk medicine. It has been well known since antiquity. Green plants are applied in East Asia as a cure for measles. The fruits are reported to have carminative, diuretic, tonic, stomachic, antibilious, refrigerant, anticatarrhal, antispasmodic, galactagogue, emmenagogue and aphrodisiac effects. The essential oil from the fruits is used in the flavour industry, for various basic and luxury foods, to some extent in medicine too, and in cosmetic perfumery. The extraction residues are used as feed for ruminants. In the USA the regulatory status 'generally recognized as safe' has been accorded to coriander fruits (GRAS 2333) and coriander fruit oil (GRAS 2334).

There is a lack of research regarding methods of prevention and control for C. sativum.

Propagation and Planting

Coriander is propagated by seed. A heat treatment of the fruits after harvest or before sowing, either artificially or by exposure to the sun, will promote physiological ripening and break dormancy. Before sowing the fruits are sometimes split into mericarps, which enhances the germination rate and allows better distribution of the plants. For fruit production plant density should be 15-40 for small-seeded coriander, 75 plants per m² for large-seeded coriander, and even higher for the production of the green herb.

In vitro production of active compounds

In vitro culture of the callus derived from the root of coriander has been shown to contain geraniol; none of the other flavouring principles associated with the spice could be detected.

Husbandry

Weeding is carried out twice; the first weeding in the young crop is particularly important. When fruit production is the aim and heavy branching is developing, thinning is sometimes practised. Coriander is usually grown as a rain-fed crop, sometimes irrigation is applied during establishment. Phosphorus and potassium are often limiting nutrients, while the demand for nitrogen is not very high.

Harvesting

For use as a green herb the entire, young plants are usually uprooted about 60 days after sowing. In the large-scale production of leaves in southern Russia, several cuts are possible if suitable genotypes are used. It is also possible to combine the harvest of fruits with some earlier cuts of leaves. For harvesting fruits, entire plants are uprooted or cut at the base when the fruits of the primary umbel are ripe and shatter when touched.

Due to the non-simultaneous ripening of the umbels of different order, plants are gathered in sheaves for further ripening and drying in the field. Threshing has to be done carefully, so that fruits do not split.

Yield

For use as a culinary herb fresh coriander yields of 24 t/ha have been reported. The yield of fruits can exceed 4 t/ha. Rainfed crops usually produce 400-700 kg/ha of fruits, irrigated crops usually 2 t/ha.

Handling after Harvest

Split fruits are usually not accepted on the world market for medicinal purposes. Thoroughly dried fruits, stored under dry conditions, will maintain the essential oil for several years without loss. Once the fruits have been crushed, the essential oil will quickly disappear.

Coriander thrives well in temperate regions, tropical highlands and the subtropics. For fruit production, plant density should be 15-40 for small-seeded coriander, 75 plants per m² for large-seeded coriander, and even higher for the production of the green herb.

Weeding is carried out twice; the first weeding in the young crop is particularly important. When fruit production is the aim and heavy branching is developing, thinning is sometimes practised. Phosphorus and potassium are often limiting nutrients, while the demand for nitrogen is not very high. Coriander prefers sandy loam, but can also be grown successfully on well-drained loam and clay soils. For germination and growth, temperatures between 17 and 27°C are required.

During the seedling and juvenile stage, the plants need adequate water supply. After stem elongation coriander is resistant to drought. Coriander is usually grown as a rain-fed crop, sometimes irrigation is applied during establishment.

For fruit production it takes about 90-140 days from sowing to harvesting. For the production of leaves, several cuts are possible when the right cultivars are used.

Principal sources: Ravindran (2017)

Fresh coriander leaves are highly perishable produce with a very short shelf life under ambient conditions.

Modified atmosphere packaging is one of the techniques adopted to enhance the shelf life of coriander leaves. Leaves can also be preserved using (a) UV-C light (short UV wavelength of 200-400 nm), where the UV light acts as a physical method for microbial disinfection, and (b) 1-methylcyclopropene (1-MCP), which delays ethylene-induced senescence by delaying chlorophyll degradation.

Studies of air drying of coriander leaves showed that the suitable drying temperature to obtain a quality product was between 40 and 50°C. Overall, the results obtained indicated that as aroma, colour and medicinal properties (all heat-sensitive properties) provide high market value to coriander leaves, to prevent the loss of these properties and to preserve them, drying should be done at a low temperature for a longer period of time. Microwave drying has been shown to help retain the colour and nutritional qualities of coriander leaves better than convective drying.

For crops grown for the fruits, due to the non-simultaneous ripening of the umbels of different order, plants are gathered in sheaves for further ripening and drying in the field. Threshing has to be done carefully, so that fruits do not split.

Principal sources: Ambrose et al. (2016)

Many improved cultivars, suitable for regional and local agroclimactic situations have been developed and released for cultivation in India. Some of the more important ones are: ‘Hisar anand’, ‘Hisar sugandhi’, ‘Hisar surabhi’, ‘Azad dhania’, ‘Pant haritima’, ‘CIMPO-33’, ‘ACR-01-256’, ‘Sindhu’, ‘Swathi’, ‘Sadhana’, ‘RCr-446’, ‘RCr-436’, ‘RCr-41’, ‘Rajendra swathi’, ‘Guj-Cor-1’, ‘Guj-Cor-2’, etc. Some of the cultivars commonly grown in other countries include: ‘Santo’, ‘Cilantro Oaxaca’, ‘Calypso’, ‘Slow bolt’, ‘Lemon’, ‘Leisure’, ‘Confetti’, ‘Caribe’, ‘Indian summer’, ‘Delfino’, ‘Thuringer’, ‘Xiang cao’, etc. ‘CDC Major’ and ‘CDC Minor’ are the cultivars grown in Canada.

Principal sources: Ravindran (2017)

Coriander is propagated by seed. A heat treatment of the fruits after harvest or before sowing, either artificial or by exposure to the sun, will promote physiological ripening and break dormancy. Before sowing the fruits are sometimes split into mericarps, which enhances the germination rate and allows better distribution of the plants.

Germination of coriander occurs at temperatures above 4°C, but is optimal at 17-20°C for genotypes with small fruits and at 22-27°C for genotypes with larger fruits. Sowing is therefore possible at any time, provided that the water supply during the juvenile period is sufficient.

Coriander leaves have good nutritional value. This herb has a high content of vitamins A, K and C, minerals such as iron, calcium and magnesium, and more antioxidants than most fruits and vegetables. The leaves also contain 5% fat, 22% protein, sugars, coumarins and other phytochemicals, including glycosides and chlorogenic and caffeic acids.

The aroma of coriander leaves is mainly due to the content of aldehyde compounds with 6-10 carbon atoms, particularly decyl and nonyl aldehydes, and 2-decenoic acid, decanoic acid (also known as capric acid) and tetradecenoic acid. The quantity of volatile oil in the leaves is lower than in the fruit and it contains decyl and nonyl aldehydes and linalool.

Principal sources: Ambrose et al. (2016)

The production of high-quality, convenient, processed coriander leaves poses unique challenges to food processors, which include the destruction of enzymes and substrates, loss of chlorophyll and formation of unwanted secondary metabolites. As a result, senescence and off-flavours may develop during respiration. Also, the exudates from the surface constitute a favourable medium for bacterial and fungal growth. When the material is handled, there are further opportunities for contamination and growth of microflora, and yet more health hazards may occur. Besides these problems, the leaves are highly perishable due to their high water content. Hence, it is essential to mitigate damage by proper handling and postharvest processing techniques.

Fresh coriander leaves are much used in soups and salsas, and have resulted in outbreaks of foodborne illness. High rates of Salmonella and Shigella have been reported on coriander leaves and, hence, it has become essential to remove such foodborne pathogens. Various studies have demonstrated that irradiation with up to 3 kGy γ-radiation effectively inactivated foodborne parasites without a major loss of volatile compounds.

There is no reported toxic effect or interactions from the use of coriander and it is regarded as safe for human consumption. No toxic effect is reported in studies involving coriander seed oil and its major component linalool. Studies affirm the safety of coriander, its oil and its major components. Coriander oil is irritating to rabbits but not to humans; it does not sensitize humans.

Principal sources: Ambrose et al. (2016); Ravindran (2017)

Although coriander is cultivated and consumed all over the world, it is difficult to obtain reliable information on production and trade. The worldwide annual area of coriander is estimated at 550,000 ha, yielding about 600,000 t of coriander fruits. Most of the crop is used as a spice, but about 10% is raw material for the distillation of essential oil, 100 t of which is traded every year. The industrial extraction of the essential oil is important in East Europe and several industrialized countries. The main producers of fruits are Ukraine, Russia, India, Morocco, Argentina, Mexico and Romania. The main importers of coriander fruits are Sri Lanka, the USA, UK, the Netherlands, Germany and Japan.

FAO statistics lump coriander with anise, badian (star anise) and fennel. The world production of these spices together rose from 372,685 t in 1993 to 940,500 t in 2013, with Asian countries accounting for over 75% of production. The top producer in 2013 was India, producing over 546,000 t, of which over 211,000 t were exported.

The area dedicated to coriander as a fresh culinary herb may be estimated at 20,000 ha, but this figure should be viewed with some caution, since production is mostly for household consumption or local markets. A market for dried coriander leaves has emerged in some industrialized countries (for example, the USA imports these from Mexico).

See FAOSTAT for current production and trade statistics.

It is expected that the market for coriander as a culinary herb will increase in industrialized countries. However, the quality parameters for this use are still unknown, and the agronomic requirements have still to be established. At present, linalool derived from petrochemicals is cheaper than linalool distilled from coriander fruits, but consumer preference for the special qualities of natural flavours may bring about a shift in demand.

Considering that the seeds of C. sativum are a global commodity and because it will continue to be cultivated around the world, areas for recommended research in the future include risk assessment and impacts of the species in places where it is known to be weedy, as well as methods of prevention and control.

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