Rosa damascena (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

habit of flowering branch.

Rosa L. cv. group Damascena

Protologue: Sp. pl.: 491 (1753), Gen. pl. ed. 5: 217 (1754); cv. group name proposed here.

Family: Rosaceae

Chromosome number: 2n= 28 (tetraploid)

Synonyms

• Rosa damascena Miller (1768),
• R. gallica L. var. damascena Voss (1894),
• R. damascena Miller var. trigintipetala (Dieck) Koehne (1893).

Vernacular names

• Damask rose, pink damask rose (En).
• Rose de damas, rose de tous les mois, rose de puteaux (Fr)
• Indonesia: kembang eros, bunga ros
• Malaysia: bunga ayer mawar, ros, gul
• Cambodia: kolaab
• Laos: kuhlaab
• Thailand: ku-laap-on (northern), kulaap mon (central), yee sun (Bangkok)
• Vietnam: huong.

Origin and geographic distribution

The damask rose is only known from cultivation and its exact origin is not known. It probably originated as a hybrid in the Anatolian region in Turkey, but semi-wild plants (escapes from cultivation) are also found in the Caucasus, Syria and Morocco. The damask rose is known from ancient times and was introduced early from Turkey into Europe and the Middle East, where Iran has been a centre of rose cultivation and rose oil production for centuries. In the Balkans and the Mediterranean it is cultivated as a source of rose oil. The most important growing areas are in Bulgaria, Turkey, southern Russia and Morocco. Elsewhere it is mainly grown as an ornamental. In South-East Asia damask rose is only occasionally cultivated as an ornamental.

Uses

Damask rose is the most important rose grown for its essential oil. On water distillation it yields rose oil and rose water (mostly from the flowers, rarely from the leaves); on solvent extraction it yields rose concrete and rose absolute. Rose oil is commercially the most important product (for cv. group Damascena it is also called rose otto or rose attar) and it is one of the oldest and most valuable perfumer's materials. Because differences in odour exist between rose oils from different origins, in commerce the oil is usually also named by the country of origin, e.g. rose oil Bulgaria. Rose oil is virtually indispensable in perfumery and cosmetics, either as a primary scent or as a modifier. In flavourings it is often used to modify a primary taste and has many applications in sweets, confectionery and tobacco products. The fruit can be processed to make jam or syrup with high vitamin C content. Rose petals can be crystallized with sugar to make a sweetmeat; dried, they are added to drinks as a flavouring, while after extraction with boiling water the residue is used to flavour confectionery and foods, especially in the Middle East and India. Petals are macerated in sesame oil to make a hair-oil in India and Malaysia. Damask rose is an officinal in medicine and is used as a fungicide and insecticide. Preparations of flowers, fruits and roots are said to be astringent. A tonic made by steeping fruit in boiling water for 5 minutes is drunk hot to alleviate the effects of a cold.

Production and international trade

World production of rose oil and rose concrete was estimated at 15-20 t in 1986 with Turkey, Bulgaria, Russia, Morocco, France and Italy as the largest producers. For the damask rose alone, oil production in Bulgaria in 1994-1995 was estimated at 750-1000 kg (down from 3 t in 1984 before the start of the economic reforms). Oil produced in Russia is mainly traded and consumed locally. The bulk of all export is to France, the United States, Switzerland and the United Kingdom. In 1991 the United States imported 4.5 t rose oil with a total value of 6 million US$.

Properties

Analysis has revealed more than 300 constituents in rose oil, most in very small proportions, but many of them important for the depth of the oil's fragrance. The major constituents are citronellol and stearoptene (non-volatile). The ratio of the three main terpene alcohols, citronellol to geraniol and nerol (the C:G+N ratio), is of major importance in determining the quality of rose oil. The major constituents (more than 1%) of damask rose oil are: citronellol, geraniol, nerol, linalool and phenylethyl alcohol. Bulgarian rose oil is pale yellow to yellow-green; fresh oil is often greener because of the presence of azulenes which gradually decompose over time; when cooled below 20°C white or colourless crystals of stearoptene precipitate out; the remaining liquid is known as elaeoptene. Stearoptene is odourless and constitutes 15-25% of the oil; on cooling below 16°C the oil solidifies into a translucent mass with surface crystals. The oil has an intense warm, deep floral, waxy odour, slightly spicy, very rich with traces of honey and a rosy-aldehydic dry-out lasting about 5 days. Rose oil does not reflect the true scent of rose flowers, since certain aroma components, particularly phenylethyl alcohol, are partially lost during distillation. Rose oil is slightly soluble in water, very slightly soluble in alcohol, but soluble in fatty oil and chloroform. Rose concrete is a waxy solid, dark yellow to brown-orange, with a melting point of 45-55°C, used in similar products as the essential oil, but is mainly extracted to produce rose absolute. Rose absolute is an orange-yellow to orange-brown viscous liquid, usually with a richer odour than rose concrete. The main uses are the same as for rose oil and concrete, but because of its strong concentration it is normally used very diluted in the end-products. Rose concrete and absolute, like rose oil, are marketed under the rose name and country of origin. In the United States, rose oil Bulgaria has been "generally recognized as safe" (GRAS No 2988).

See also: Composition of essential-oil samples and the Table on standard physical properties.

Adulterations and substitutes

Because rose oil is expensive, commercial lots are frequently extended with a wide range of natural compounds of different origin or with synthetics, but most alter the oil's natural odour or persistence perceptibly. Several formulations to compound synthetic rose fragrances have been published and even modifications to match the odour of rose oil of different origins. Oil from various Rosa species is marketed as otto or attar of roses: R. centifolia L. in Morocco and France, R. gallica L. in Russia and Egypt, R. rugosa Thunb. ex Murray and other Rosa species in China, but experienced perfumers can readily identify these.

Description

• Robust, erect, multi-stemmed and branched shrub, 1-2 m tall, with well-developed, extensive root system. Prickles usually many, unequal, straight to slightly curved, reddish-brown when young, grey when old.
• Leaves alternate, compound, with 5-7 leaflets, waxy; stipules almost entire, elongated; petiole with red-brown hairs; leaflet elliptical, 2-7 cm × 1.5-5 cm, margin serrate, usually hairy below, not glandular.
• Inflorescence a terminal raceme or thyrsus, bearing 3-10 flowers, rarely more.
• Flowers up to 8 cm in diameter, often double, very fragrant, usually pinkish; pedicel up to 7 cm long, with many glandular bristles; hypanthium glandular-bristly outside, hairy inside; sepals triangular, broadly cuspidate, reflexed during anthesis, caducous afterwards, glandular; petals red to white, preferably rosy-pink to rosy-red, usually 20-30 normal and 5-10 deformed ones; stamens 100-120; pistils many, styles free, hairy.
• Fruit an ovoid hip, up to 2.5 cm long, fleshy, bristly, light to dark red, 1-3-seeded.
• Seed rounded triangular, 3-5 mm long, brownish.

Growth and development

A period of winter dormancy is essential for damask rose to induce bud development. In Europe, adventitious buds for flowering shoots form in the crown of annual branches in spring. Bud formation is best with night/day temperatures of 3-4°C/15-16°C. In the inflorescence the flowers bloom consecutively; main flowering period in Europe is June-July, in India March-April and September-October. Flowering period is directly influenced by climatic conditions, but is normally completed in 20-25 days. It can be affected by growth regulators like ethephon. The optimum temperature range is 15-20°C and optimum relative humidity 60%. All flower parts contain essential oil which generally reaches its maximum when the petals become cup-shaped and the stamens bright yellow; the petals contain most oil. Whole flowers are picked for rose oil; young buds are selected for highest yield of concrete. Most of the fruits are shed before ripening. The economic life of a plantation is 10-12 years, flower yield normally increases during the first 5-7 years and then declines gradually until the plantation becomes unprofitable. Individual plants can live for up to 50 years.

Other botanical information

"What's in a name? that which we call a rose, by any other name would smell as sweet..." This horrifying - for taxonomists - statement of Shakespeare in "Romeo and Juliet" was unintentionally also visionary, because the correct scientific name for the damask rose has always been disputed. R. damascena Miller is most often used in the literature, but R. × damascena Miller is also used, to express its hybrid origin. Unfortunately, the name R. damascena was already used by Herrmann in 1762 for a different taxon (included in R. centifolia L.), thus invalidating Miller's name. Instead of looking for the correct botanical binomial it seems better to classify the damask roses as what they really are: a group of cultivars grown especially for their scent or essential oil. It is undisputed that damask roses have a hybrid origin but the parentage is not absolutely clear. The influences of the wild roses R. centifolia L., R. gallica L. and R. phoenicea Boiss. seem most certain, but R. alba L., R. canina L. and R. moschata J. Herrm. have also been mentioned.

Several subgroups can be distinguished within the cv. group Damascena:

• cv. subgroup Autumn Damask (other names: four seasons or monthly rose, R. damascena Miller var. semperflorens (Loisel) Rowley, R. bifera Poiret, R. calendarum Borkh.). When pruned appropriately, this group of cultivars is able to produce flowers in 2 or 3 flushes during the growing season and could even be forced to flower in the winter months. Their supposed parentage is R. gallica L. × R. moschata J. Herrmann.

• cv. subgroup Versicolor (other names: York or Lancaster rose, R. damascena Miller f. versicolor West.). This group is summer-flowering and has variegated flowers.

• cv. subgroup Trigintipetala (other names: Kazanlik rose, pink damask rose, R. gallica L. var. damascena f. trigintipetala Dieck). Summer-flowering roses but without variegated flowers. To this group belongs the most important rose cultivar for essential oil production in the world, "Trigintipetala" (30 petals), mainly grown in the Kazanlik area of Bulgaria, and in Turkey. Other well known cultivars are "Kazanlik" and "Iskra".

• cv. subgroup Portlandica (other names: portland rose, scarlet four seasons, R. portlandica West.). A group of low-growing roses with bright red, semi-double flowers in clusters of 3-4, flowering from midsummer into autumn. The Damask perpetuals or portland roses have been derived from this group.

Most other roses cultivated commercially for their essential oil are cultivars of R. alba L. (the "white cottage rose" is hardier and more resistant to unfavorable climatic factors and is grown around fields of damask cultivars in Bulgaria), R. centifolia L. (the "light pink cabbage rose" is grown mainly in France, Morocco ("rose de mai") and Spain), R. gallica L. (particularly in Russia and Egypt) and R. rugosa Thunb. ex Murray (especially in China).

Ecology

Cv. group Damascena is adaptable to a wide range of environmental conditions. In general a mild climate is preferred with no extremes of temperature and long periods of warm, sunny weather and an evenly distributed rainfall. In Kazanlik (Bulgaria), the major cultivation area, an average spring temperature of 5-15°C is considered as optimum. Low night temperatures of 10-12°C during flowering inhibit oil synthesis, but night temperatures up to 20°C increases it. Regular rainfall is important, especially in spring and early summer, and a daily relative humidity in May-June of 70% is considered optimum. Waterlogging should be avoided, but damask roses can withstand waterlogging to a considerable extent. Hot dry periods during flowering rapidly reduce oil yield by evaporation. Shade is inimical to flowering in Bulgaria, but in India, where temperatures in the sun are higher, shade is essential. Frost during early vegetative growth or bud formation causes extensive damage. Mature plants are frost resistant but pruned ones require protection in areas with severe winter frosts. A deep, fertile loam (pH 6-7.5) is most suitable for commercial rose growing but climate is more important than soil type. In India, alkaline saline soils of pH 8-9 are well suited for damask rose growing.

Propagation and planting

Propagation is by cuttings or division (splits) of mature damask rose plants, but grafting or budding on rootstock of other rose species (e.g. R. multiflora Thunb. ex Murray) is also common. Micropropagation is a possibility but is not yet commercially practised. Cuttings are preferably 20-30 cm long, 2-noded, taken from shoots which begin to lignify. The lower leaves are removed, the end treated with a rooting compound and the cutting is then inserted into the ground for up to half its length, in a nursery. After 1 year the rooted cuttings can be transplanted to the field. In India a bed of 20 m × 5 m accommodates 10 000 cuttings, sufficient for planting 1 ha. Splits are obtained by dividing mature plants so that each split has a section of root attached. In Bulgaria 1 ha produces sufficient splits to plant 2 ha and the splits are often planted directly in the field. Before establishing a plantation it is advisable to apply manure and plough in (e.g. 50 t/ha). Deep ploughing is necessary to facilitate root development. Hedge planting is most popular, with rows 2-2.5 m and plants 1-1.5 m apart. Roses are seldom underplanted or intercropped.

Husbandry

Weed control is essential in damask rose; it is done manually or shallowly mechanically, or even by mulching with black plastic or applying herbicides. Irrigation is necessary when rainfall is insufficient. Soil moisture should be maintained at 85% capacity. Young bushes are pruned annually in early summer to promote uniform branching, and all flower buds are removed in the first and sometimes also the 2nd year. Seasonal pruning is done to remove dead or diseased shoots. In the 3rd year flowering is allowed and harvesting may start. Older plants may be cut back severely (e.g. to 15 cm) to promote new and vigorous growth. This is usually done at least once in a plantation's life, but a less severe pruning every 3 years is usually adequate. Harvested roses in Bulgaria extract yearly per ha 64 kg N, 8.7 kg P and 36 kg K. In India, up to 10 t/ha manure is applied annually and in Egypt whatever is available. Once growth has started N is normally supplied as a top dressing in one or more applications. In Bulgaria 300 kg/ha ammonium nitrate is applied yearly, in India 200 kg/ha calcium ammonium nitrate is preferred. Phosphate is usually applied as triple-superphosphate. K applications depend on soil type; sulphate of potash is preferred. Mg is often deficient and should be applied when lacking.

Diseases and pests

Damask roses suffer much from many diseases and pests and control measurements are absolutely necessary to limit losses. Large differences in the prevalence of pathogens exist between regions and cultivars. Important diseases include: rose rust (Phragmidium spp.), which attacks all aboveground parts, forming orange-coloured pustules; black spot (Marssonina rosae), which mainly affects leaves and young shoots, forming circular black spots; powdery mildew (Sphaerotheca spp., Uncinuma spp.), which mainly damages leaves and young shoots, covering them with a white powder; damping off (Pythium spp.) and root rot (Phytophthora spp.), which mainly occur in rooted cuttings and splits. Major rose pests that damage the roots include: root mealy bugs (Rhizococcus spp.), root aphids (Maculolachnus spp.), rootworms (Paria spp.) and nematodes (Pratylenchus spp.). Stems and branches are attacked by stem borers and girdlers (Agrilus spp., Oberea spp.), scale insects (Aulacaspis spp.) and stem sawflies (Syrista spp.). Leaves are liable to damage by caperpillars (Argyrotaenia spp., Sibine spp., Parasa spp., Archips spp.), beetle larvae (Macrodactylus spp.), rose slugs (Endelomyia spp.) and whiteflies (Bulgarialeurodes spp., Trialeurodes spp.). Flowers are attacked by cerculios (Rhynchites spp.), chafer beetles (Macrodactylus spp. and Cetonia spp.), rose beetles (Nodonota spp.), midges (Dasineura spp.) and thrips (Thrips spp.).

Harvesting

Flowers of damask rose are usually picked manually (nipped off just below the calyx) which is very labour intensive and limits expansion of rose cultivation. Simple hand-held mechanical pickers are coming in use. Picking should be done between 5 and 10 a.m. when the flowers open and oil content is highest. Whole, fully open flowers should be selected because they have the highest oil content, not buds or previous day flowers. An experienced worker can pick 3-6 kg per hour.

Yield

Annual damask rose flower yield averages 1-3.5 t/ha and 2-4 t are required to produce 1 kg oil. Average annual flower yield per ha is 2-3 t in Bulgaria, 2-2.5 t in Turkey, 1.5-2 t in Russia, 1-1.5 t in India. In Morocco, flower yield of R. centifolia averages 2.5 t/ha; in Egypt, flower yield of R. gallica is 2.5-4 t/ha. In Egypt R. gallica yields 2.2 kg concrete or 1 kg absolute from 1000 kg flowers; in Morocco 1.8 kg concrete or 0.9 kg absolute is obtained from 1000 kg R. centifolia flowers.

Handling after harvest

Damask rose flowers should be transported to the distillery without delay, but storing bagged flowers in clean, cold (4-10°C) water maintains oil content and quality for up to 3 days. Spreading flowers for short periods (not more than 24 hours) in layers in a cool shady place retains most of the oil. Rose oil is produced by a 2-stage distillation process because many of the aroma compounds of roses are water-soluble. In the initial stage whole flowers are water distilled and the distillate is separated into "decant" or "first oil" and the remaining liquid. The latter is redistilled to produce "second oil" and "rose water". The "decant" and "second oil" are combined to make "rose oil". After distillation the oil should be stored in full, airtight, opaque containers and kept cool. Oil exposed to air and light quickly deteriorates. In India rose water is more important than rose oil and the first distillate is not returned to the still but sold directly as rose water, e.g. as "rose water 20/40", i.e. 20 l of distillate from 40 kg flowers. Solvent extraction of rose flowers is now frequently used. Rose concrete is obtained by extraction of rose flowers, often with hexane; rose absolute by extraction of the concrete with alcohol. Water distillation yields 0.01-0.04% of essential oil. Solvent extraction typically yields about 10 times the amount obtained by distillation, or 0.1-0.2% concrete. Concrete, in turn, yields about 50% absolute.

Genetic resources

Extensive living rose collections, including damask roses, exist at e.g. Gardens of the Rose, St Albans, Hertfordshire (United Kingdom); Das Rosarium, Sangerhausen (Germany); Botanical Gardens, Wageningen Agricultural University (the Netherlands), and the Botanic Garden of Gap-Charance (France).

Breeding

Although most damask cultivars are tetraploids, diploid, triploid and pentaploid cultivars are known. The genetic background of most damask rose cultivars is obscure and most probably there is ample scope for improvement of many characteristics (e.g. oil content, disease resistance, flowering time, drought resistance, cold requirement for flowering) to create cultivars most suited to local circumstances. Because of easy vegetative propagation, multiplication of interesting improved selections poses no problems.

Prospects

Damask rose oil production is especially interesting for those areas where labour costs are low and where enough land is available. Attractive prices for the oil are guaranteed if the quality is high. Damask rose is not suited for small-scale production, since considerable investments are required for the application of advanced distillation or extraction techniques. Potentially it could be an interesting plantation crop for higher altitude areas in South-East Asia and much could be learned from experiences in India.

Literature

• Bayrak, A. & Akgül, A., 1994. Volatile oil composition of Turkish rose (Rosa damascena). Journal of Science and Food in Agriculture 64: 441-448.
• Bean, W.J., 1980. Trees and shrubs hardy in the British Isles. 8th Revised edition (Clarke, D.L. & Taylor, G., editors). Vol. 4 (Ri-Z). John Murray, London, United Kingdom. pp. 35-205, particularly pp. 79-84.
• Guenther, E., 1952. The essential oils. Vol. 5. Oil of rose. D. van Nostrand Company, New York, United States. pp. 3-48.
• Kalkman, C., 1973. The genus Rosa in Malesia. Blumea 21: 281-291.
• Krüssmann, G., 1974. Rosen, Rosen, Rosen, unser Wissen über die Rose [Roses, roses, roses, our knowledge about the rose]. Verlag Paul Parey, Berlin & Hamburg, Germany. 447 pp., particularly pp. 209-217.
• Lawrence, B.M., 1993. Essential oils 1988-1991. Rose oils and extracts. Allured Publishing Corporation, Carol Stream, United States. pp. 144-165.
• Touw, M., 1982. Roses in the Middle Ages. Economic Botany 36: 71-83.
• Weiss, E.A., 1997. Essential oil crops. CAB International, Wallingford, United Kingdom. pp. 393-416.
• Widrelchner, M., 1981. History and utilization of Rosa damascena. Economic Botany 35: 42-58.

Composition of essential-oil of Rose oil, Bulgaria

• 32.0% citronellol
• 19.0% alkanes & alkenes
• 15.7% geraniol
• 8.7% nerol
• 2.7% linalool
• 2.3% methyl eugenol
• 1.6% ethanol
• 1.2% 2-phenylethanol
• 1.0% (E,E)-farnesol
• 0.7% α-terpineol
• 0.7% geranyl acetate
• 0.6% eugenol
• 0.5% citronellyl acetate
• 0.5% β-caryophyllene
• 0.4% cis-rose oxide
• 0.3% terpinen-4-ol
• 0.2% α-humulene
• 0.2% α-pinene
• 0.2% dibutyl phthalate
• 0.2% trans-geranic acid
• 0.2% benzyl tiglate
• 0.2% (E)-nerolidol
• 0.2% 1-hexanol
• 0.2% trans-rose oxide
• 0.2% α-guaiene
• 0.2% (Z,E)-farnesol
• 0.1% γ-cadinene
• 0.1% p-cymene-8-ol
• 0.1% geranylacetone
• 0.1% 2-phenylethyl isobutyrate
• 0.1% β-damascenone
• 0.1% 2-phenylethyl benzoate
• 0.1% myrcene
• 0.1% nerol oxide
• 0.1% methyl geranate
• 0.1% methanol
• 0.1% neryl acetate
• 0.1% benzyl benzoate
• 0.1% 2-phenylethyl acetate
• 0.1% 2-methylbutanol
• 0.1% 3-methylbutanol
• 0.1% (E)-3-hexenol-1
• trace β-pinene
• trace limonene
• trace (E)-β-ocimene
• trace 2-phenylethyl 2-methylbutyrate
• trace acetaldehyde
• trace trans-linalool oxide (unknown isomer)
• trace nonanal
• trace geranial
• trace 1,8-cineole
• trace heptanal
• trace 6-methyl-5-hepten-2-one
• trace 2-undecanone
• trace ethyl dodecanoate
• trace 2-pentadecanone
• trace γ-terpinene
• trace terpinolene
• trace benzaldehyde
• trace ethyl benzoate
• trace 6-methyl-5-hepten-2-ol
• trace 2-tridecanone
• trace farnesene (unknown isomer)
• trace α,p-dimethylstyrene
• trace pentanal
• trace 1-pentanol
• trace 1-heptanol
• trace α-terpinene
• trace para-cymene
• trace (Z)-β-ocimene
• trace decanal
• trace undecanal
• trace neral
• trace ylangene
• trace acids and esters
• trace hexanal
• trace menthol
• trace 1-decanol
• trace (E)-anethol
• trace 1,1-diethoxy ethane
• trace geranic acid
• trace citronellic acid
• trace zingiberene
• trace benzyl alcohol
• trace 1-octanol
• trace menthone
• trace isomenthone
• trace 2-methylbutanal
• trace 3-methylbutanal
• trace methyl salicylate
• trace rosefuran
• trace menthyl acetate
• trace 2-butanol
• trace 2-methylpropanol
• trace acetone
• trace benzyl methyl ether
• trace prenol
• trace methyl cis-geranate
• trace 1-butanol
• trace citronellyl hexanoate
• trace p-1-menthenal-9
• 92.1% total

Source: Kovats, 1987.

Physical properties of essential oil

rose oil, Bulgaria

• Relative density : 0.848-0.861
• Refractive index : 1.453-1.464
• Optical rotation : -5 to -2
• Miscibility in ethanol :
• ISO/EOA : ISO 9842 '91

See comments : Physical properties of essential oils (PROSEA)

Sources of illustrations

Bois, E. & Trechslin, A.M., 1964. Rozen [Roses]. Dutch edition by De Langhe, J.E. Artis, Brussels, Belgium. Plate 2, p. 9. Redrawn and adapted by P. Verheij-Hayes.

Authors

P.C.M. Jansen