Artemisia dracunculus (PROSEA)
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Introduction |
- Protologue: Sp. pl.: 849 (1753).
- Family: Compositae
- Chromosome number: 2n = 18, 36, 54, 72, 90
Synonyms
- Artemisia inodora Willd. (1809),
- A. redowskyi Ledeb. (1815),
- Oligosporus condimentarius Cass. (1826).
Vernacular names
- Tarragon, estragon, dragon mugwort (En, Am)
- Estragon, dragon (Fr).
Origin and geographic distribution
The origin of tarragon is not known with certainty; it may be Siberia. It has a very wide distribution, from central Europe and western and northern Asia (Asia Minor, Mongolia, northern China, Siberia) to western North America (up to Colorado and Texas). It is also widely cultivated, e.g. in Europe (France, Germany, Italy, the Netherlands), United States, Brazil, Egypt and India. In South-East Asia it is locally cultivated in the mountainous regions of Java (Indonesia) and it has been introduced into the Philippines.
Uses
The fresh or dried leaves of tarragon have a sweet anise-like scent and a peculiar bittersweet flavour and are used for seasoning foods like salads, soups, stews and sauces. They are particularly suited to flavour chicken, egg and lobster preparations. The popular tarragon vinegar is prepared by adding the herb to wine vinegar. Due to its low sodium content tarragon can be safely used as a substitute for sodium chloride in sodium-restricted diets. Medicinally, tarragon is believed to have aperient, stomachic, stimulant and febrifuge properties. On steam distillation, the leaves yield an essential oil (known as tarragon or estragon oil) which is used in perfumery, in canning pickles and in flavouring vinegar and liqueurs. Tarragon oil also possesses bactericidal and nematicidal activity. In the United States the regulatory status "generally recognized as safe" has been accorded to tarragon (GRAS 3043) and tarragon oil (GRAS 2412). The maximum permitted level of tarragon leaves in food products is 0.3%, and the highest level of the oil is 0.04% in baked goods.
Production and international trade
The major markets and their annual tarragon consumption are: France (80-100 t), the United States (40-50 t), Germany (10-80 t), the Netherlands (25 t), Belgium (10-15 t), the United Kingdom (10 t), Switzerland (2 t), Japan (2 t). Annual world production of tarragon oil is about 10 t, with a value of US$ 0.8 million.
Properties
Per 100 g edible portion, dried ground tarragon contains approximately: water 5-8 g, protein 23-25 g, fat 7-7.5 g, carbohydrates 43-45 g, fibre 7 g, ash 12 g (Ca 1.1 g, Fe 32 mg, K 3.0 g, Mg 0.3 g, Na 62 mg, P 0.3 g, Zn 4 mg), niacin 9 mg, riboflavin 1 mg, thiamine 0.3 mg, vitamin A 4200 IU, vitamin C 12 mg. The energy value is about 1385 kJ/100 g. The essential-oil content of dried tarragon ranges from 0.2%-1.0%.
The two cultivated types, i.e. French or German tarragon and Russian tarragon, differ in essential-oil components. French tarragon oil consists mainly of methyl chavicol (estragole), trans-ocimene + γ-terpinene, cis-ocimene, and limonene. On the other hand, the major components of Russian tarragon oil are elemicin, sabinene, trans-ocimene + γ-terpinene, methyl eugenol, myrcene, cis-ocimene, citronellyl acetate, and terpine-4-ol. There are also differences in the flavonol profile of the air-dried stems and leaves of the two types. While Russian tarragon contains patuletin glycosides, quercetin and quercetin glycosides, French tarragon possesses only quercetin glycosides.
A monograph on the physiological properties of tarragon oil has been published by the Research Institute for Fragrance Materials (RIFM).
Composition
French tarragon oil (Source: Werker et al., 1994)
- 77.0% methyl chavicol
- 9.0% (E)-β-ocimene
- 8.1% (Z)-β-ocimene
- 2.5% limonene
- 0.9% γ-terpinene
- 0.5% eugenol
- 0.5% methyl eugenol
- 0.2% nerol
- 0.2% elemicin
- 0.1% β-pinene
- 0.1% myrcene
- 0.1% para-cymene
- 0.1% linalool
- 0.1% terpinen-4-ol
- 0.1% geraniol
- 0.1% α-pinene
- 0.1% camphene
- 0.1% sabinene
- 0.1% α-terpinene
- 0.1% terpinolene
- 0.1% 1,8-cineole
- 99.8% total
French tarragon oil (from United States) (Source: Tucker & Maciarello, 1987)
- 80.0% methyl chavicol
- 7.0% (E)-β-ocimene
- 6.6% (Z)-β-ocimene
- 2.5% limonene
- 0.6% α-pinene
- 0.5% methyl eugenol
- 0.5% γ-terpinene
- 0.3% eugenol
- 0.1% myrcene
- 0.1% methyl isoeugenol
- 0.1% β-pinene
- 0.1% sabinene
- 0.1% linalool
- 0.1% elemicin
- trace camphene
- trace terpinolene
- trace geraniol
- trace nerol
- trace trans-alloocimene
- trace terpinen-4-ol
- trace 1,2-cineole
- trace trans-isoelemicin
- trace α-thujene
- trace α-phellandrene
- trace α-terpinene
- trace para-cymene
- trace citronellyl acetate
- trace cis-alloocimene
- 98.8% total
Adulterations and substitutes
Tagetes lucida Cav. (Compositae), the sweet-scented marigold from Mexico and Central America, also known as Mexican tarragon, resembles tarragon with respect to flowers and fragrance and is often used as a substitute for it. It grows well in the Philippines.
Description
- Perennial herb, 0.5-1.5 m tall, glabrous, strongly aromatic or almost odourless. Rhizome woody, up to 1.5 cm thick, sometimes with well developed underground shoots. Stem erect, solitary or several, branched, furrowed, lower branches not flowering.
- Leaves alternate, subsessile, entire, simple, olive-green, the lowest ones deciduous and sometimes ending in 2-5 narrow lobes; blade linear-lanceolate to almost linear, 2-10 cm × 1-14 mm, margin sometimes weakly serrate.
- Inflorescence a drooping subglobose head, 2-4 mm in diameter, aggregated at apices of stem and branches into racemes which together give a paniculate appearance; peduncle 0-5 mm long; involucre 2-4 mm long, outer bracts oblong to lanceolate, inner ones rounded-ovate, margin membranous; outer florets usually 7(-15), pistillate and fertile, with tubular yellowish, whitish or reddish corolla 1 mm long and 2 spreading, often twisted style branches; disk florets 11-14(-20), bisexual but functionally male, corolla conical, 5-toothed, up to 2 mm long, anthers linear, pistil rudimentary with more or less connate style branches.
- Fruit an achene, flat-ovoid, 0.6-1 mm long, finely grooved, glabrous, brown.
Growth and development
When started from cuttings, first leaves can be harvested 2-3 months after the plant has established. Although tarragon is a perennial plant and could be maintained for many years, the essential-oil content gradually diminishes in older plants. Therefore, commercial plantings are renewed every 3-4 years.
Shoot growth in tarragon is affected by daylength and cold pretreatment. Plants exposed to 16 hours of light grow 2-3 times faster than those given only 8 hours of light. Cumulative herbage production under long days is further enhanced if plants are given a cold pretreatment of 4°C for 6 weeks.
Other botanical information
Tarragon is a variable species with wild and cultivated forms and its taxonomy is not yet well established. In the cultivated forms two large groups can be distinguished:
- cv. group French Tarragon (also called cv. group German Tarragon). This group comprises the most important spice cultivars and is mostly cultivated in Europe and the United States. Its cultivars are tetraploid (2n = 36), they seldom produce normal flowers and never viable seed. They are propagated by stem and rhizome cuttings. The leaves are glabrous, very fragrant and the major component of the essential oil is methyl chavicol. A well known cultivar is "Epicure”.
- cv. group Russian Tarragon (synonyms: A. dracunculoides Pursh, A. glauca Pall. ex Willd.). This group comprises the much less fragrant cultivars, is more closely related to the wild forms and is mainly cultivated in northern Asia. Its cultivars are decaploid (2n = 90), they flower and produce viable seed normally and propagation is by seed. The leaves are mainly glabrous but bear some stellate hairs. The major components of the essential oil are elemicin and sabinene.
Several varieties have been distinguished in the wild forms, mainly on the basis of length and colour of stem, juvenile hairiness, size of flowerheads and structure of aggregate inflorescences, e.g. var. humilis Kryl. (20-30 cm tall, narrow paniculate inflorescence), var. pilosa Krasch. (densely hairy when young), var. pratorum Krasch. (stem up to 2 m tall, leaves partly 2-3-lobed, inflorescence long and loose), var. redowskyi Ledeb. (yellow-brown stem, inflorescence spreading paniculate), var. turkestanica Krasch. (leaves and heads large). In northern Asia, the wild plants often become troublesome weeds in pastures. Because of their strong rhizome they are resistant to trampling and difficult to eradicate while their forage value is minimal.
Ecology
Tarragon is primarily a crop of temperate climates. It thrives in well-drained, light soil under full sun. It requires a soil pH of 6.3-7.8. It should be protected from excessive moisture, requiring an annual precipitation of only 300-1300 mm. It can survive light frost (wild forms even severe frost) and plant growth is stimulated by long days. In the Philippines tarragon is commercially grown in Silang, Cavite, at 600 m altitude and with average annual temperatures of 23-25°C.
In Asia and North America, wild plants occur in open, rather dry places, e.g. in meadows and steppe zones, from the plains to moderate elevations in the mountains.
Propagation and planting
Propagation of tarragon is normally by stem or rhizome cuttings. Stem cuttings 15 cm long are taken from shoot tips and rooted in mist beds or in coarse river sand with regular watering. Presoaking the basal ends in 100 ppm indolebutyric acid (IBA) overnight or dipping them in 2000 ppm IBA for a few seconds enhances rooting. In rhizome cuttings, pieces of the main rhizome, 5 cm long, together with roots and a new shoot, are severed from the mature plant. Planting material is established in polybags in the nursery prior to field planting.
In vitro propagation has also been reported for tarragon using leaf and shoot tip explants. Good shoot proliferation has been obtained on media such as Linsmaier-Skoog, White, Murashige-Skoog with various addenda. Rooting succeeds well using Techniculture plugs saturated with 1 ml of a solution with 1 mg naphthaleneacetic acid (NAA) per l.
In commercial farms in the Philippines garden plots are prepared by ploughing 2-3 times and incorporating chicken manure and rice hulls before the final ploughing. Tarragon is planted at 20-25 cm distance in rows 25-40 cm apart.
In vitro production of active compounds
The production of methyl chavicol and methyl eugenol, two important components of tarragon essential oil, has been demonstrated in callus cultures obtained from leaf explants. The amount detected in vitro was up to 2000-fold less than the level accumulated in the plant. The presence of exogenous NAA in the culture was inhibitory to this accumulation. The detection of the metabolites in disorganized cells revealed that differentiation of secretory structures was not an absolute requirement for the synthesis of these compounds. The low levels detected were attributed to possible volatilization, active metabolism and autotoxicity of the compounds.
Husbandry
During the initial stage of growth, it is appropriate to mulch tarragon with straw. This prevents weed proliferation, conserves soil moisture and lowers the soil temperature, particularly during the dry season. Regular watering is necessary. A crop of tarragon lasts about 3 years.
Diseases and pests
No serious diseases and pests have been reported for tarragon. Damage can be caused on the leaves by the rust Puccinia dracunculina, stalk and root rot is caused by Sclerotinia minor and the beetle Cantharis lateralis may feed on the leaves. Fungicides and insecticides easily control diseases and pests but are seldom used.
Harvesting
Once the crop is well established, green leaves and tender tops may be harvested at intervals during the growing season. Per year 2-3 harvests may be obtained.
In commercial farms in the Philippines, the first harvesting is carried out 2 months from transplanting. Time of harvesting, however, is often dictated by the market demand, which is particularly high during the Christmas season.
Yield
No reliable information is available on the yield of tarragon under South-East Asian conditions. Commercial plantations outside South-East Asia show an average fresh herb yield of 2.5-3.7 t/ha in the first year and 5-6 t/ha in the second year of planting. An annual essential-oil yield of 40 l/ha is possible.
Handling after harvest
In the Philippines, freshly cut tarragon shoots are bundled and immediately packed in styrofoam boxes for delivery to market outlets. The dried product is obtained by air-drying the shoots under shade or by placing them in artificial dryers with temperatures not exceeding 43 °C. Commercial quantities of dried herb are preferably stored in well-closed barrels.
When tarragon oil is desired the dried herb is steam-distilled for 1-1.5 hours. The oil is stored in well-filled bottles and protected from light.
Genetic resources and breeding
In Europe small germplasm collections of tarragon are present in the Czech Republic, Germany, Lithuania, Portugal, Russia and Slovakia. There are no known breeding programmes.
Prospects
The potential of the food service market and the prospects for culinary herbs in South-East Asia appear to be bright. The production of culinary herbs can be quite lucrative, if it is accompanied by an effective marketing system. Tarragon is one of the important culinary herbs being grown in South-East Asia for the food service market.
Literature
- Cotton, C.M., Evans, L.V. & Gramshaw, J.W., 1991. The accumulation of volatile oils in whole plants and cell cultures of tarragon (Artemisia dracunculus). Journal of Experimental Botany 42: 365-375.
- Cotton, C.M., Gramshaw, J.W. & Evans, L.V., 1991. The effect of α-naphthalene acetic acid (NAA) and benzylaminopurine (BAP) on the accumulation of volatile oil components in cell cultures of tarragon (Artemisia dracunculus). Journal of Experimental Botany 42: 377-386.
- Mackay, W.A. & Kitto, S.L., 1987. Rapid propagation of French tarragon using in vitro techniques. Acta Horticulturae 208: 251-261.
- Polyakov, P.P., 1995. In: Shishkin, B.K. & Bobrov, E.G. (Editors): Flora of the U.S.S.R. Vol. 26. Translated into English from original Russian edition. Bishen Singh Mahendra Pal Singh, Dehra Dun, India & Koeltz Scientific Books, Koenigstein, Germany. pp. 606-610.
- Prakash, V., 1990. Leafy spices. CRC Press, Boca Raton, Florida, United States. pp. 95-98.
- Tateo, F., Santamaria, L., Bianchi, L. & Bianchi, A., 1989. Basil oil and tarragon oil: composition and genotoxicity evaluation. Journal of Essential Oil Research 1: 111-118.
- Vienne, M., Braemer, R., Paris, M. & Couderc, H., 1989. Chemotaxonomic study of two cultivars of Artemisia dracunculus L.: "French” and "Russian” tarragon. Biochemical Systematics and Ecology 17(5): 373-374.
- Werker, E., Putievsky, E., Ravid, U., Dulai, N. & Katzir, I., 1994. Glandular hairs, secretory cavities and the essential oil in leaves of tarragon (Artemisia dracunculus L.). Journal of Herbs, Spices and Medicinal Plants 2(3): 19-32.
Sources of illustrations
Artemisia dracunculus: Hegi, G., 1987. Illustrierte Flora von Mittel-Europa {Illustrated flora of Central Europe]. 2nd edition (Editor: Wagenitz, G.). Vol. 6(4). Verlag Paul Parey, Berlin, Germany. Fig. 345, p. 636 (habit flowering stem, flower head); Cronquist, A., 1955. Compositae. In: Hitchcock, C.L., Cronquist, A., Ownbey, M. & Thompson, J.W. (Editors): Vascular plants of the Pacific Northwest. Part 5 (2nd printing, 1969). University of Washington Press, Seattle, United States. p. 65 (lobed basal leaves, florets). Redrawn and adapted by P. Verheij-Hayes.
Authors
- C.C. de Guzman & R.A. Reglos
