- Protologue: Sp. pl.: 588 (1753); Gen. pl., ed. 5: 256 (1754).
- Family: Labiatae
- Chromosome number: x = 15; 2n = 30 (O. vulgare)
Major species and synonyms
- Origanum majorana L., Sp. pl.: 590 (1753), synonyms: Majorana hortensis Moench (1794), Origanum majoranoides Willd. (1800), O. dubium Boissier (1879).
- Origanum vulgare L., Sp. pl.: 590 (1753), synonyms: O. hirtum Link (1822), O. gracile Koch (1848), O. viride (Boissier) Halacsy (1902).
- Marjoram, sweet marjoram (En).
- Marjolaine (Fr).
- Oregano, wild marjoram (En).
- Mediterranean or European oregano (Am). Origan (Fr)
- Philippines: oregano, suganda, torongil de Limon.
Note: Commercially the term "oregano” has a wide meaning and includes more than 60 species of different genera and families.
Origin and geographic distribution
Origanum is predominantly a Mediterranean genus, especially of the eastern part (more than 75% of the species). O. majorana originated in Cyprus and adjacent southern Turkey; it occurs subspontaneously in former Yugoslavia, Italy, Corsica, southern Spain, southern Portugal, Morocco and Algeria; it is also cultivated in those areas and in many countries in Europe, America and Asia, including South-East Asia. O. vulgare most probably originated in the Mediterranean, but is widely distributed now from the Azores, Madeira and the Canary Islands, throughout Europe and the Mediterranean to West and Central Asia and Taiwan. It is also cultivated in many countries of the world, including South-East Asia (e.g. Indonesia, the Philippines) where it is more important than O. majorana.
Most Origanum species (especially their leaves and flowers) have been used since ancient times as culinary and medicinal herbs, as ornamental garden plants and some also as producers of a dye. The use as culinary herb of both major species mentioned here is most important. Marjoram has a delicate and sweet flavour. The fresh leaves are used as a garnish for salads while the dried herb is popular for seasoning soups, stews and poultry dishes. In the United States the regulatory status "generally recognized as safe” has been accorded to marjoram (GRAS 2662), marjoram oil (GRAS 2663) and marjoram oleoresin (GRAS 2659). The oil is extensively used as a flavour component in major food products; the maximum permitted level in food is about 0.004%. The maximum permitted level as a fragrance constituent in perfume compounds for soaps, detergents, cosmetic and extrait perfumes is 0.6%.
Oregano has a stronger and more robust flavour than marjoram. It is popularly known as the "pizza” herb because of the dependence of the dish on oregano for full flavour. It combines well with any tomato dish. The regulatory status of oregano in the United States is "generally recognized as safe” (GRAS 2660). The essential oil is used for scenting soap and as an ingredient in liqueur and wine. In the Philippines, oregano is one of the most important herbs used in first-class hotels, restaurants and fast-food establishments. The fresh herb is more popular and expensive than the dried herb. Both herbs are also used to make a kind of tea, and a good quality honey can be obtained from the flowers. The sap of oregano also yields a red dye.
Medicinally, oregano is less important than it used to be. It was, for example, used as a stimulant, carminative, tonic and to cure asthma, coughs, indigestion, rheumatism, toothache, headache and spider bites. Although its use as culinary herb is currently most important, there is renewed interest in the bactericidal, fungicidal, antiviral, nematicidal, insecticidal and anti-oxidant activities of Origanum essential oils. In some places stored plant products are traditionally protected against insect damage by spraying with Origanum essential oil or powdered dried herb.
Production and international trade
Annual consumption in the United States, Japan and some major markets in Europe in the late 1970s varied from 880-1685 t for marjoram and 2070-2820 t for oregano. In later years consumption increased considerably. The average annual import of oregano in the United States alone between 1991-1995 amounted to 4000 t, of which about 80% came from Turkey, the rest mainly from Greece, Israel and Morocco. Average annual export of oregano from the largest producer Turkey in the years 1989-1995 amounted to 4500 t. Annual consumption in the 1990s amounted to 500 t in France, 600 t in Germany, 500 t in United Kingdom and 150 t in the Netherlands. The value of world production of essential oil in the 1990s was US$ 2.1 million for marjoram and US$ 0.4 million for oregano.
In the Philippines, oregano is cultivated mainly for the fresh herb market. The area of cultivation is very small. Annual consumption (based on purchases of several food service establishments in Metro Manila) is about 1.6 t, mainly as fresh herb (about 75%).
There have been many chemical analyses of marjoram and oregano, especially of their essential oils. Variation in published figures is large, mainly due to different methods of analysis, wide differences in origin and developmental stage of the material used, and often questionable identity of the samples analysed. The figures presented here are intended to give an indication, and should be interpreted with great care. Per 100 g edible portion dried marjoram leaves contain approximately: water 8 g, protein 13 g, fat 6 g, carbohydrates 40 g, fibre 20 g, ash 12 g (Ca 2.0 g, Fe 83 mg, K 1.5 g, Mg 350 mg, Na 80 mg, P 310 mg), vitamin C 50 mg. The energy value is about 1140 kJ/100 g. A yellow or greenish-yellow essential oil can be obtained by steam distillation. The fresh herb yields 0.3-0.4% essential oil, the dried herb 1-6%. The major constituent of the essential oil is terpinen-4-ol. A monograph on the physiological properties of marjoram oil has been published by the Research Institute for Fragrance Materials (RIFM).
Per 100 g edible portion the composition of dried, ground oregano is approximately: water 7 g, protein 11 g, fat 10 g, carbohydrates 49 g, fibre 15 g, ash 7 g (Ca 1.6 g, Fe 44 mg, K 1.7 g, Mg 270 mg, Na 15 mg, P 200 mg). The energy value is about 1280 kJ/100 g. The fresh herb yields 0.1-0.2% essential-oil, the dried herb 0.1-6%. The flowers contain more oil than the leaves. The major constituent of the essential oil is carvacrol.
The seed of marjoram and oregano is very light; the 1000-seed weight for both is about 0.2 g.
Origanum majorana: Marjoram oil (from Portugal) (Source: Oberdieck, 1981.)
- 36.3% terpinen-4-ol
- 15.9% cis-sabinene hydrate
- 9.5% para-cymene
- 8.2% α-terpineol
- 3.9% linalool
- 3.7% trans-sabinene hydrate
- 3.7% cis-p-menth-2-en-1-ol
- 3.5% linalyl acetate
- 2.5% sabinene
- 2.5% bicyclogermacrene
- 2.0% β-caryophyllene
- 1.2% p-cymen-8-ol
- 1.0% caryophyllene oxide
- 0.9% carvone
- 0.6% trans-p-mentha-2,8-dien-1-ol
- 0.5% limonene
- 0.5% geranyl acetate
- 0.4% terpinen-4-yl acetate
- 0.3% α-pinene
- 0.2% myrcene
- 0.2% neryl acetate
- 0.2% copaene (unknown isomer)
- 0.2% methyl carvacrol
- 0.2% α-terpinyl acetate
- 0.1% α-thujene
- 0.1% β-pinene
- 0.1% terpinolene
- 0.1% 1,8-cineole
- 0.1% α-humulene
- 0.1% 1-octenol-3
- 0.1% camphene
- 0.1% α-phellandrene
- 0.1% α-terpinene
- 0.1% β-phellandrene
- 0.1% (Z)-β-ocimene
- 0.1% (E)-β-ocimene
- 0.1% γ-terpinene
- 0.1% geraniol
- 0.1% β-bisabolene
- 0.1% carvacrol
- 0.1% cuminaldehyde
- 0.1% (Z)-3-hexenol
- 0.1% 3-octanol
- 0.1% (E)-2-hexenal
- 0.1% α,p-dimethylstyrene
- 0.1% cis-alloocimene
- 99.5% total
Origanum majorana: Marjoram oil (Source: Fischer et al., 1987.)
- 25.0% cis-sabinene hydrate
- 22.1% terpinen-4-ol
- 10.9% γ-terpinene
- 6.8% α-terpinene
- 6.6% trans-sabinene hydrate
- 5.5% sabinene
- 3.3% α-terpineol
- 3.0% cis-sabinene hydrate acetate
- 2.7% limonene
- 2.3% terpinolene
- 1.7% myrcene
- 1.6% trans-p-mentha-2,8-dien-1-ol
- 1.0% linalool
- 0.6% cis-p-menth-2-en-1-ol
- 0.5% linalyl acetate
- 93.5% total
Origanum vulgare: Greek oregano oil (from Turkey) (Source: Baser et al., 1994.)
- 40.0% carvacrol
- 20.0% thymol
- 10.0% para-cymene
- 9.0% γ-terpinene
- 4.8% cis-sabinene hydrate
- 1.8% cis-dihydrocarvone
- 1.8% α-pinene
- 1.7% myrcene
- 1.4% α-terpinene
- 1.0% β-caryophyllene
- 0.8% trans-dihydrocarvone
- 0.8% α-terpineol
- 0.8% trans-sabinene hydrate
- 0.7% 1,8-cineole
- 0.6% β-bisabolene
- 0.6% caryophyllene oxide
- 0.6% 1-octenol-3
- 0.3% camphene
- 0.3% linalool
- 0.2% p-cymen-8-ol
- 0.2% γ-elemene
- 0.2% α-humulene
- 0.2% limonene
- 0.2% methyl carvacrol
- 0.2% (E)-β-ocimene
- 0.2% β-pinene
- 0.2% terpinen-4-ol
- 0.2% sabinene
- 0.2% terpinolene
- 0.1% γ-cadinene
- 0.1% β-farnesene
- 0.1% heptadecane
- 0.1% isoborneol
- 0.1% β-phellandrene
- 0.1% spathulenol
- 0.1% δ-3-carene
- 0.1% methyl 2-methylbutyrate
- 0.1% T-cadinol
- 0.1% carvacryl acetate
- 0.1% (E)-2-hexenal
- 0.1% (Z)-β-ocimene
- trace linalyl acetate
- trace 6-methyl-3-heptanol
- trace α-bergamotene
- trace calamenene
- trace carveol
- trace nonanal
- trace α-phellandrene
- 99.8% total
Adulterations and substitutes
There are many plants which have a similar scent or flavour to marjoram and oregano and which can be found as adulteration or as substitute. In commerce more than 60 plant species (belonging to 17 genera in 6 families) are offered as oregano. The most important ones are: Lippia graveolens Kunth (Verbenaceae; Mexican oregano; so similar to true oregano that the commercial herb trade does not distinguish between these); Origanum dictamnus L. (Crete dittany); O. onites L. (Turkish oregano); O. syriacum L., and Thymus capitatus (L.) Hoffm. & Link (Labiatae; Spanish oregano). Plectranthus amboinicus (Loureiro) Sprengel is known as oregano in the Philippines, but is used as a medicinal plant.
- Subshrubs or perennial herbs, variously hairy to glabrous, often glaucous, glandular. Stems usually several and square, ascending or erect, branched.
- Leaves opposite, simple, subsessile to petiolate, glandular.
- Inflorescence a verticillaster, aggregated in loose to dense spikes which are again arranged into paniculate or corymbiform units; bracts always distinct from the leaves in shape, size and often also in texture and colour, usually imbricate.
- Flowers 2 to several per verticillaster, bisexual or female; calyx usually tubular, regularly 5-toothed or 1-2-lipped; corolla usually 2-lipped, upper lip 2-lobed, lower lip 3-lobed; stamens 4 in 2 pairs (didynamous), the lower 2 longest; style as long as or longer than corolla, 2-lobed at apex.
- Fruit composed of 4 separate, ovoid, brown nutlets, each one 1-1.5 mm × 0.5 mm.
- Subshrub, up to 0.8 m tall with strong roots and hairy, brown stem.
- Leaves up to 30 pairs per stem; petiole 0-15 mm long; blade roundish to ovate, 3-35 mm × 2-30 mm, margin entire, whitish to greyish, tomentellous, glandular (up to 1500 glands per cm2), veins not raised.
- Spike subglobose, ovoid or quadrigonous-cylindrical, 3-20 mm × 3 mm, whitish or greyish, tomentellous, often 3 or 5 closely together at a branch; bracts (2-)6(-30) pairs per spike, ovate, obovate or rhomboid, 2-4 mm × 1-3 mm, whitish or greyish, tomentellous.
- Calyx tubular, 2-3.5 mm long, tomentellous; corolla 3-7 mm long, white to yellowish, the 2 lobes of upper lip 0.2 mm long, the 3 lobes of lower lip subequal, 0.5-2 mm long; stamens protruding, upper pair up to 4 mm, lower pair up to 5 mm long; style up to 9 mm long.
- Woody perennial up to 1 m tall. Stem ascending, rooting at the base, purplish-brown, pilose to glabrous, branches up to 25 cm long.
- Leaves up to 45 pairs per stem; petiole up to 2 cm long; blade ovate to roundish, 6-40 mm × 5-30 mm, hairy to glabrous, glandular (100-2000 glands per cm2), margin entire or remotely serrulate.
- Spike 3-35 mm × 2-8 mm; bracts 2-25 pairs per spike, subovate, 2-11 mm × 1-7 mm, hairy to glabrous, purplish to greenish?
- Calyx tubular, 2.5-4.5 mm long, teeth 0.5-1 mm long, hairy to glabrous; corolla 3-11 mm long, purple, pink or white, hairy outside; lobes of upper lip 0.2-0.7 mm long; lobes of lower lip unequal, 0.5-1.7 mm long; upper pair of stamens up to 4.5 mm, lower pair up to 5.5 mm long; style up to 13 mm long.
Growth and development
In Europe, marjoram and oregano seed sown in spring reaches full flowering stage in about 2-3 months. After pollination and fertilization, seed ripens in about 1 month. Under unfavourable water conditions, hardly any normal seed develops. In Europe the growing period for marjoram and oregano is from March to November. Under favourable climatic conditions both species can be grown as a perennial crop with a lifespan of 3-4 years; often, however, both species are grown as annuals. Oregano has been reported to be affected by daylength. Plants exposed to photoperiods of 12 h or 16 h were significantly taller, had more nodes, larger leaf area, and higher shoot and root dry weight than those exposed to 8 h. Floral differentiation occurred only at photoperiods of 12 and 16 h, with a faster rate of differentiation at longer daylengths, suggesting that oregano is a long-day plant.
In oregano uptake of water and the nutrients N, P and K is highest during seed formation and lowest during flowering. The dry weight of leaves and inflorescences peaks at seed formation. The essential-oil content is highest at the initiation of flowering and decreases when seeds start to develop.
In oregano gynodioecy may occur. It is estimated that in Europe up to 50% of the plants in some populations have functionally female flowers.
Other botanical information
The genus Origanum comprises 38 species, mainly occurring in the Mediterranean region, and most species have a very limited distribution area. In addition to the species there are also 17 known hybrids.
Cultivated plants of O. majorana often behave as annual or biennial herbs with a less compact habit, longer branches, a less dense indumentum with larger leaves and longer petioles than wild ones.
O. vulgare with its wide distribution, is a very variable species, bearing a heavy load of different species and subclassification names in the literature, mainly based on differences in indumentum, number of glands on leaves, bracts and calyx and in size and colour of bracts and flowers. None of the subclassifications is satisfactory because O. vulgare is one complex species with numerous intermediate forms between distinguishable extremes. The most widely accepted subclassification distinguishes 6 subspecies:
- subsp. glandulosum (Desf.) Ietswaart: plant hirsute; leaves not glaucous; inflorescences very wide; leaves, bracts and calyces conspicuously glandular punctate; bracts 1.5-6 mm × 1-3 mm, shorter than calyx; distributed in Tunesia and northern Algeria.
- subsp. gracile (Koch) Ietswaart: plant pilosellous or glabrescent; branches and spikes slender; leaves glaucous; leaves and calyces conspicuously glandular punctate; bracts 1.5-6 mm × 1-3 mm; distributed in eastern Turkey, northern Iraq, Iran, Afghanistan and southern central Russia.
- subsp. hirtum (Link) Ietswaart (in the literature often mentioned O. heracleoticum auct., non L.): plant hirsute; leaves not glaucous; inflorescences compact; leaves, bracts and calyces conspicuously glandular punctate; bracts 1.5-6 mm × 1-3 mm, as long as or longer than calyx; distributed over the eastern Mediterranean area; this taxon is known as "Greek oregano” and is considered to be the best quality oregano (called "rigani” in Greece).
- subsp. virens (Hoffm. & Link) Ietswaart: leaves and calyces inconspicuously glandular punctate; inflorescence compact; bracts 3.5-11 mm × 2-7 mm, glabrescent, yellow-green; flowers white; distributed in the western part of the overall species area, Azores, Canary Islands, Madeira, Portugal, Spain and western North Africa.
- subsp. viride (Boissier) Hayek (synonym: O. heracleoticum L.): leaves and calyces inconspicuously glandular punctate; inflorescence not compact; bracts 2-8 mm × 1-4 mm, pilosellous, green; flowers white; distributed widely, from Corse to eastern China.
- subsp. vulgare: leaves and calyces inconspicuously glandular punctate; bracts 2-11 mm × 1-7 mm, purple; flowers pink; distributed all over the northern part of the area, from Britain and Scandinavia through Europe to Asia and Taiwan; it has also naturalized in North America.
O. vulgare is also widely cultivated as ornamental; cultivar "Aureum” has golden-yellow leaves and "Humile” is a dwarf form up to 20 cm tall.
There are hardly any officially registered marjoram and oregano cultivars. Commercial unofficial cultivars are numerous and are a source of endless confusion. An internationally accepted official cultivar registration authority is badly needed. There are 3 official cultivars of marjoram in Germany: "Francia” (developed from Hungarian material), "Miraz” (from Poland) and "Marcelka” (from Czech Republic).
Some other well-known but minor Origanum species are:
- O. dictamnus L., only known from Crete (Greece) where it grows wild and cultivated, is the very famous medicinal herb mentioned by most classic Greek authors as having the property to stop bleeding and to cure stomach-ache. The herb can easily be recognized from its woolly hairs, which are branched. It is also used as culinary herb.
- O. onites L., occurring in southern Greece and many Greek islands, western and southern Turkey and on Sicily (Italy) is the "pot marjoram”, cultivated in France and on Cyprus as a culinary herb.
- O. syriacum L., occurring in the eastern part of the Mediterranean, is the "hyssop” of the bible, used as a culinary herb and medicinally.
Marjoram and oregano are sun-loving plants. Being temperate and subtropical in origin, they can survive cold weather conditions. Oregano, however, is more hardy than marjoram. In its natural habitat marjoram often grows on dry, rocky, limestone soil, at altitudes of 100-1500 m, oregano on limestone soil up to 4000 m altitude. Marjoram prefers rich light soils, with a pH of 5.8-7.2, oregano prefers light dry soils with a pH of 4.5-8.7. For both crops the mean water requirement during the growing period is 500-1000 mm, and average temperature should not be lower than 15°C, although plants may survive much worse conditions. In the tropics both crops grow best at altitudes of 1000-2000 m. In the Philippines oregano is cultivated in Silang, Cavite, which is at 600 m altitude with an average annual temperature of 23-25°C.
Propagation and planting
Marjoram and oregano are mainly propagated by seed. Seed dormancy sometimes occurs. If sown in germination boxes, seedlings emerge in 14-21 days. Both crops can be planted directly in the field, preferably at distances of 50-60 cm × 20 cm. In the Philippines seeds are sown very densely: in rows 40 cm apart and about 25 plants per m of row. Alternatively, the plants are initially grown in the greenhouse and transplanted to the field when having 10-15 leaves. Oregano can also be propagated by stem cuttings and by division of plant clusters.
Rapid multiplication of oregano can be achieved through regeneration of plants from cotyledonary callus optimally induced on Gamborgs' medium. Subsequent shoot induction and root initiation can be achieved on the same medium.
In vitro production of active compounds
The production of volatile oil has been reported in undifferentiated callus culture of oregano; the amount obtained, however, was minute and only the chemical component carvacrol was identified to be present in the oil.
Weed control is very important for both species and weeding is needed about 3 times per growing season. Normally Origanum is grown in dry climatic conditions and survives under natural rainfall. Higher yields, however, are only obtained if the crop is irrigated during dry periods. Oregano and marjoram respond well to fertilizer application. For marjoram, herbage yield was highest at 60 kg/ha N. Fertilizing oregano with 100 kg/ha N immediately before planting and after harvest was found to increase dry herbage and oil yield. Essential-oil yield was not affected by N. Application of composted cow manure has also been shown to increase herbage and essential-oil yields in both crops.
In Germany, marjoram is cultivated as an annual in a crop rotation before wheat and barley and after legumes or potatoes.
Diseases and pests
In general, marjoram and oregano do not suffer from serious diseases or pests. Marjoram may suffer from Alternaria fungi at the seedling stage, and on oregano a rust disease of little importance caused by Puccinia menthae has been observed.
For essential-oil production Origanum is preferably harvested in full bloom, for herb production at the beginning of flowering. In practice, material for the fresh-herb market is harvested at any time throughout the growing season after the plant has established. In small commercial plantings in the Philippines there are two harvests per month.
For large-scale production of dried herb and extraction of essential oil, the first harvest of leaves and tender tops of both marjoram and oregano occurs just as flowering commences. The first harvest may occur 3-5 months from field planting. Plants are cut 5-7 cm above the soil. Depending on cultivation methods and growing conditions, there can be 2-4 harvests per year.
Yield figures greatly depend on method of cultivation (annual or perennial, plant density). In a 2-year cycle the yield of dried leaves of marjoram varies from 1.4-3.4 t/ha for the first year and 2.8-5.2 t/ha for the second year of cultivation. Calculated annual yield of essential oil averages 73 l/ha. In oregano, yield of dried leaves may range from 2.6-3.2 t/ha and 3.8-5.0 t/ha for the first and second year of cultivation, respectively. Calculated annual yield of essential oil varies from 158-316 l/ha.
In Italy, total dried product yield of a 4-year Origanum crop is estimated at 20 t/ha. There are two harvests per year (June and October). The oil content of the leaves in the October harvest is very low.
Handling after harvest
Post-harvest handling depends on the desired state of the final product: fresh or dried. The herb should be free from soil particles, weeds and other dirt.
Fresh herbs are bundled together, packed and kept at low temperatures until sold. The quality of both herbs can be maintained for some time when stored at 10°C. To prevent weight loss and to retain turgidity, fresh oregano is placed in polybags or styrofoam boxes or it is put with its basal stems in water that is changed daily.
Oregano and marjoram are dried using rack dryers placed in a well-ventilated room. The racks are made of wire mesh built to convenient sizes and stacked with adequate space between them to allow free air flow. To speed up drying and to obtain a better quality material, a heat source is provided, with the temperature maintained at 29-43°C. When the herb is dry, leaves and small stems are separated from the more woody portion by flailing. The dried product is then stored in polypropylene sacks.
In most countries where Origanum occurs naturally, at least some germplasm is conserved. Major collections are available in France (Conservatoire des Plantes Médicinales, Aromatiques et Industrielles, Milly-La-Foret, 95 accessions), Germany (Institute for Plant Genetics and Crop Plant Research, Gatersleben, 21 accessions), Italy (Institute of Agronomy, University of Palermo, 214 accessions) and Turkey (Izmir Plant Genetic Resources Department, Aegean Agricultural Research Institute, 119 accessions). The increasing interest worldwide for Origanum material since the 1980s, resulted in over-harvesting from the wild in several countries (e.g. Greece, Morocco, Turkey and Albania) and hence there is a serious threat of genetic erosion of Origanum species. In 1994 the Oregano Genetic Resources Network was established by IPGRI.
Breeding programmes are ongoing in most Mediterranean countries, e.g. in France, Israel and Greece, for marjoram also in Germany. Breeding efforts are promising because both species show a wide variability. Main targets are: stable cultivars with higher herb and oil yield, drought resistance, better quality of the herb and the oil. The often occurring male sterility can be exploited to make artificial crossings.
Worldwide interest in marjoram and oregano is increasing. In South-East Asia these culinary herbs are also becoming more popular. A good example is the use and cultivation of oregano in the Philippines. The demand, however, is not yet great enough to warrant large-scale commercial production. More research is needed to investigate the feasibility of cultivation and of creating a market for marjoram and oregano in other countries of South-East Asia.
- Ietswaart, J.H., 1980. A taxonomic revision of the genus Origanum (Labiatae). Leiden Botanical Series No 4. Leiden University Press, Leiden, the Netherlands. 153 pp.
- Kumari, N. & Saradhi, P.P., 1992. Regeneration of plants from callus cultures of Origanum vulgare L. Plant Cell Reports 11: 476-479.
- Kuris, A., Altman, A. & Putievsky, E., 1980. Rooting and initial establishment of stem cuttings of oregano, peppermint and balm. Scientia Horticulturae 13: 53-59.
- Mamaril, C.B.C., 1996. The food service market potential of culinary herbs in selected areas of Metro Manila. BS Thesis, Department of Agricultural Economics, University of the Philippines at Los Baños, the Philippines. 129 pp.
- Miller, R.A., 1992. The potential of herbs as a cash crop. Ten Speed Press, Berkeley, California, United States. 230 pp.
- Padulosi, S. (Editor), 1997. Oregano. Promoting the conservation and use of underutilized and neglected crops 14. Proceedings of the IPGRI International Workshop on Oregano, 8-12 May 1996, CIHEAM, Valenzano (Bari), Italy. Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany and International Plant Genetic Resources Institute, Rome, Italy. 176 pp.
- Putievsky, E. & Basker, D., 1977. Experimental cultivation of marjoram, oregano and basil. Journal of Horticultural Science 52: 181-188.
- Rhyu, H.Y., 1979. Gas chromatographic characterization of oregano and other selected spices of the Labiatae. Journal of Food Science 44: 1373-1378.
- Svoboda, K.P., Finch, R.P., Cariou, E. & Deans, S.G., 1995. Production of volatile oils in tissue culture of Origanum vulgare and Tanacetum vulgare. Acta Horticulturae 390: 147-152.
Sources of illustrations
Origanum vulgare: Ross-Craig, S., 1967. Drawings of British plants. Part 24. Labiatae. G. Bell & Sons, London, United Kingdom. Plate 9. Redrawn and adapted by P. Verheij-Hayes.
- C.C. de Guzman & P.C.M. Jansen