Rhododendron ponticum (rhododendron)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Rainfall Regime
- Soil Tolerances
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Environmental Impact
- Impact: Biodiversity
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Rhododendron ponticum L.
Preferred Common Name
Other Scientific Names
- Rhododendron lancifolium Moench
- Rhododendron speciosum Salisb.
International Common Names
- English: pontic rhododendron; purple-flowered rhododendron
- French: rhododendron pontique
- Portuguese: adelfeira
Local Common Names
- Germany: Pontische alpenrose
- Italy: rhododendro pontico
- Netherlands: pontische rododendron
- RHOPO (Rhododendron ponticum)
Summary of InvasivenessTop of page R. ponticum has become established in the UK and other parts of Europe where it is threatening natural and semi-native habitats and the associated flora and fauna. In its native range, R. ponticum is also spreading and causing problems in the forests of Turkey where again it displaces native vegetation. It smothers the forest floor when it becomes established and shades out all other vegetation. Present control methods are expensive and labour-intensive and classical biological control is not really an option due to the many associated species in the genus. A proposed method of biocontrol would be to use a native wood-rotting pathogen formulated as a stump treatment, but more research and work is needed.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Ericales
- Family: Ericaceae
- Genus: Rhododendron
- Species: Rhododendron ponticum
Notes on Taxonomy and NomenclatureTop of page The genus Rhododendron is the largest in the Ericaceae family with 1200 species. There are two subspecies of Rhododendron ponticum, subsp. baeticum and subsp. ponticum, with a number of varieties recorded, R. ponticum var. album, a form with white flowers, R. ponticum var. cheiranthifolium a compact variety with narrow and wavy leaves, R. ponticum var. lancifolium compact with narrow leaves, R. ponticum var. variegatum has variegated foliage, and R. ponticum var. heterophyllum from Turkey newly recorded in 2000 (Terzioglu et al., 2001).
DescriptionTop of page R. ponticum is a large evergreen shrub, which can grow 2-8 m high. The shrub can consist of several major axes forming from an irregular base (Cross, 1975). R. ponticum forms a compact shrub in open areas, while in the shade it adopts a larger spread when competing for light and other resources. The leaves are glabrous, dark green glossy above, paler beneath, oblong to elliptic in shape, up to 22 cm long. The wood is hard and light brown with the bark being rough, brown to dark brown. The flowers can vary in color from lilac pink to various light and dark shades of purple, spotted with brown and orange. Flowers occur in compact racemes borne from the glabrous pedicel. The flowers present 10 stamens with curved filaments. The fruit is a woody capsule that can persist for up to three years bearing multiple seeds.
Plant TypeTop of page Broadleaved
DistributionTop of page R. ponticum subsp. ponticum has a wide native distribution covering an area south of the Black Sea, including Bulgaria, Turkey (Bean, 1976), Georgia (USDA-ARS, 2003), the Krasnodar region of southern Russia (Czekalski, 1998; USDA-ARS, 2003) and Lebanon (Cross, 1975), and may be or may have been also native to Syria. Small pockets of native habitat are found in south western Spain and central and southern Portugal where R. ponticum subsp. baeticum is found (Milne and Abbott, 2000). R. ponticum has spread to other parts of Europe but not to other continents, is now naturalized in Belgium and France (Tutin et al., 1972; Cross, 1975) and invasive in the UK. It is found throughout Ireland (Kelly, 1981), Scotland, Wales and England (Cross, 1975) but grows best in the damper west of the country.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Planted||Reference||Notes|
|Georgia (Republic of)||Present||Native||Natural||USDA-ARS, 2003; EPPO, 2014|
|Lebanon||Present||Native||Not invasive||Natural||Cross, 1975; EPPO, 2014|
|Syria||Absent, unreliable record||EPPO, 2014|
|Turkey||Widespread||Native||Invasive||Natural||Ansin and Terzioglu, 1994; EPPO, 2014|
|Belgium||Present||Introduced||Not invasive||Planted||Cross, 1975; EPPO, 2014|
|Bulgaria||Widespread||Native||Not invasive||Natural||Bean, 1976; EPPO, 2014|
|France||Present||Introduced||Not invasive||Planted||Cross, 1975; EPPO, 2014|
|Gibraltar||Present||Native||Not invasive||Natural||Cross, 1975|
|Ireland||Widespread||Introduced||Invasive||Planted||Kelly, 1981; EPPO, 2014|
|Norway||Restricted distribution||Introduced||Invasive||Planted||Cross, 1975; EPPO, 2014|
|Poland||Present||Introduced||Not invasive||Planted||Czekalski, 1996; EPPO, 2014|
|Portugal||Restricted distribution||Native||Not invasive||Natural||Cross, 1975; EPPO, 2014|
|Russian Federation||Restricted distribution||EPPO, 2014|
|-Southern Russia||Restricted distribution||Native||Not invasive||Natural||Czekalski, 1996; EPPO, 2014|
|Slovakia||Restricted distribution||Introduced||Not invasive||Planted||Czekalski, 1996; EPPO, 2014|
|Spain||Restricted distribution||Native||Not invasive||Natural||Cross, 1975; EPPO, 2014|
|UK||Widespread||Introduced||1763||Invasive||Planted||Elton, 1958; EPPO, 2014|
History of Introduction and SpreadTop of page R. ponticum was first introduced to the UK, via Gibraltar in 1763 by the nurseryman Conrad Lodiges (Cronk and Fuller, 1995). By 1803, R. ponticum was being sold on London markets as a flowering pot-plant and was established throughout England as an ornamental in stately homes. Recent molecular studies support Iberia as the origin of UK material (Milne and Abbott, 2000). Ireland saw the introduction of R. ponticum around 1800 (Doyle et al., 1999) though fossil records of Irish peat deposits show R. ponticum was a native to Ireland during the Gortian Interglacial period 428,000-302,000 years ago. It is unclear when R. ponticum was first introduced into Wales, UK, though the invasiveness of the species was being documented in 1943 (Gritten, 1995; Thomson et al., 1993). It is now naturalized in Belgium and France (Tutin et al., 1972; Cross, 1975). Further spread of this shrub is possible due to its invasive characteristics, though further spread is unlikely if adequate control and management is applied in its introduced range.
Risk of IntroductionTop of page Further introduction of R. ponticum by man is likely for ornamental purposes for large gardens and as a cover for game. R. ponticum is widely available in garden centers as pot-plants and via mail order seed companies and via the Internet.
HabitatTop of page R. ponticum is a large evergreen shrub, which can grow in a variety of different habitats. The species is well suited to a wide range of temperatures and grows best in damp conditions, being intolerant of drought. In its native range, R. ponticum is present from sea level to over 2000 m altitude, occurring in deciduous and evergreen forests in the Pontic Mountain ranges of Turkey, pine woods in Lebanon and on granite slopes in Spain and Portugal. In its introduced range, R. ponticum has colonized an array of habitats from managed and ancient woodlands to moorland and urban areas in the UK, also invading peatlands, scrub woods, heathlands and woodlands (Foley, 1990; Doyle et al., 1999), and has spread from gardens to invade woodland and national parks (Thomson et al., 1993).
Habitat ListTop of page
|Coastal areas||Present, no further details|
|Cultivated / agricultural land||Present, no further details||Harmful (pest or invasive)|
|Disturbed areas||Present, no further details|
|Managed forests, plantations and orchards||Present, no further details||Harmful (pest or invasive)|
|Managed grasslands (grazing systems)||Present, no further details|
|Rail / roadsides||Present, no further details|
|Urban / peri-urban areas||Present, no further details|
|Natural forests||Present, no further details||Harmful (pest or invasive)|
|Natural grasslands||Present, no further details|
Hosts/Species AffectedTop of page R. ponticum does not pose a significant threat to plants in agricultural systems. Nevertheless, R. ponticum has become a serious pest in commercial land management (Rotherham, 1990) and has proved to have dramatic effects on habitat structure and native biodiversity in the areas where it has been introduced. Where R. ponticum is introduced in an area all plant species are threatened.
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page Pre-emergence, Seedling stage, Vegetative growing stage
Biology and EcologyTop of page Genetics
The chromosome number of R. ponticum is 2n=26.
Physiology and Phenology
The growth rate of seedlings is slow and can take up to two years for a seedling to become a juvenile bearing adult sized leaves. The growth of R. ponticum can occur throughout the growing season with defined periods of growth occurring between May and June, July-August and a third period of growth in September. The initial shoot extension takes place in early May, though under favorable conditions this may be bought forward to as early as February. In Mediterranean populations, the plant flowers over two months in late spring, though flowers can still be seen during the autumn-winter period (Mejias, et al., 2002). Flowers appear from late spring to late summer in the introduced range, though the influence of increased latitude and altitude will delay this process. The plant can extend both laterally and vertically, though the main growth form is the former as the stems lacks the strength to support large vertically growth unless supported by other vegetation or man-made structures. The root system consists of an extensive root mat laid down in the top 2-15 cm of the soil. This characteristic root system allows the shrub to exhaust the available soil oxygen thus exerting an indirect competition effect on surrounding plant species (Esen, 2000). The competitiveness of the root system is enhanced by mycorrhizal symbionts, which enhance mineral and nutrient acquisition.
Reproduction is mainly by seed with vegetative spread being limited to air layering, with branches rooting if buried in damp soil. R. ponticum flowers from the age of 12 years and pollination is assisted by insect species of the families Hymenoptera and Syrphidae. Rhododendron bushes 2 m high can produce over one million light small seeds each per annum (Shaw, 1984). The average weight of the seed varies from 0.02 to 0.19 mg depending upon location (Esen, 2000). Light is an essential prerequisite for the germination of seeds as is a temperature range of about 10-15°C.
R. ponticum is tolerant of a range of climatic conditions from as cold as -17°C to 25.9°C in its native range in Turkey to a much narrower climate in its introduced range. The species is intolerant of drought and grows best in areas of uniform damp climates. High humidity, mild winters and acidic soils are favoured for the growth of R. ponticum. The ability to tolerate dense shade gives R. ponticum a great advantage over its competitors. Even almost closed canopy conditions do not prevent this species from growing. A well drained humus soil type is the preferred conditions for optimum growth and R. ponticum will grow on other types of soils in its introduced range though not so vigorously.
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Absolute minimum temperature (ºC)||-20||0|
|Mean annual temperature (ºC)||-17||40|
|Mean maximum temperature of hottest month (ºC)||16||40|
|Mean minimum temperature of coldest month (ºC)||-17||6|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Dry season duration||0||0||number of consecutive months with <40 mm rainfall|
|Mean annual rainfall||525||1300||mm; lower/upper limits|
Rainfall RegimeTop of page Uniform
Soil TolerancesTop of page
- very acid
Special soil tolerances
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Illinoia lambersi||Herbivore||Growing point/Leaves|
|Stephanitis rhododendri||Herbivore||Growing point/Leaves|
Notes on Natural EnemiesTop of page There are few natural enemies associated with R. ponticum even in its native range. Judd and Rotherham (1992) found a total of 31 phytophagous insects associated with the shrub throughout its introduced range. The most closely associated insects include Stephanitis rhododendri, Illinoia lambersi (syn. Masonaphis lambersi) (Hemiptera) and Melolontha melolontha (Coleoptera). Farr et al. (1996) have identified a number of fungi associated with the shrub including a rust fungus from its native range in Portugal. Others include Colletotrichum spp. (leaf spot), Phytophthora cactorum (stem-rot), Armillaria mellea, and Chondrostereum purpureum has been associated with die back of Rhododendron in the UK (Strouts and Winter, 2000). Phytophthora ramorum, the fungus causing sudden oak death in the USA, was found on R. ponticum shrubs in 2003 in the UK (Anon., 2003). A disease outbreak in Windsor Great Park, Berkshire, UK showed signs of a virulent dieback, with cross sections of the diseased stems revealing cankered sections of the wood. An unusual Cryptosporiopsis sp. (Deuteromycotina: Coelomycetes) appeared to be associated with the disease symptoms.
Means of Movement and DispersalTop of page Natural Dispersal (Non-Biotic)
Natural dispersal is effective with the aid of wind and seeds can travel considerable distances, estimated at up to 1000 m, though this is considerably reduced to as little as 10 m in wooded areas (Shaw, 1984). Seeds are mature after 6 months and dispersal generally occurs 2 months after this time when the capsules open (Cross, 1981).
Vector Transmission (Biotic)
There are no known incidences of animals, other than man, acting as disseminators of seed.
There is no agricultural use for R. ponticum and therefore no agricultural practices associated with the species, but seed may be transferred by machinery involved in controlling R. ponticum infestations.
R. ponticum has only been introduced deliberately as an ornamental and then escaped accidentally from the enclosed areas. Accidental introduction may have occurred via the disposal of R. ponticum pot-plants or plant parts in landfill sites or rubbish collection sites.
R. ponticum was intentionally introduced into the UK where it was planted as an ornamental in gardens of large houses and in estates, where it provided cover for game animals. For many years, R. ponticum was more or less restricted to these artificial habitats but with the gradual erosion of large estates and the attendant workforces, the plant was allowed to spread unchecked. The warmer winters and wetter climates of the western UK appear to favor the fecundity, spread and establishment of the plant and it is in these areas where R. ponticum, within the past 40-50 years, has changed from a naturalized, prized garden plant to an invasive category 4 species (Cronk and Fuller, 1995).
Impact SummaryTop of page
|Fisheries / aquaculture||None|
ImpactTop of page The economic impact of eradicating R. ponticum in a local area can run to many millions. The cost of clearing the weed in Snowdonia National Park, Wales, UK has been estimated at over £30 million (over US$50 million) (Mabberley, 1998). R. ponticum on the small island of Hebridean, Colonsay, Scotland, UK is spreading at a rate of 1 km² every 5 years and the cost of prevention and eradication of the weed is estimated to be £120,000 (approximately US$200,000) per year for a planned 16 year programme. On the small island of Lundy, Devon, UK, 105 days work and £26,880 (approximately US$50,000) is required per year to clear R. ponticum from cliffs (Compton and Key, 1998). Toxins in the leaves of R. ponticum have been known to poison sheep, cattle (Black, 1991), goats (Humpherys, et al., 1983) and dogs (Frape and Ward, 1993) and the nectar of R. ponticum is poisonous to bees, though there are no reported costs associated with this.
Environmental ImpactTop of page R. ponticum is widely recognized as being very environmentally and ecologically damaging to semi-natural habitats, woodlands, heathlands and managed plantations. R. ponticum threatens forests throughout the UK and in its native range in Turkey (Colak et al., 1998) and where conditions are suitable for R. ponticum to grow, it will out-compete most native plant species. Once the native plants have disappeared then the associated fauna will disappear too. R. ponticum will cover the ground preventing saplings from becoming established and therefore eventually producing a monocultural stand.
Impact: BiodiversityTop of page R. ponticum has a dramatic effect on native biodiversity in areas where the plant has been introduced. Due to the spreading and competitive nature of the plant, R. ponticum can cast a dense shade in the understorey and no other plant is able to grow. Almost all plants and animals in a forest are under threat when R. ponticum is present and left to spread. Firstly the ground vegetation disappears, such as wild forest flowers, ferns and mosses. R. ponticum is posing a significant threat to the rare endemic Lundy cabbage, Conincya wrightii (Brassicaceae), and a flea beetle (Psylliodes luridipennis) associated with this plant on the island of Lundy, UK (Compton and Key, 1958). C. wrightii is restricted to the east coast of Lundy due to grazing pressure from livestock and R. ponticum is encroaching on the habitat of this rare cabbage and is threatening its existence.
Social ImpactTop of page The eradication of R. ponticum is an expensive and time-consuming process. Footpaths and parks can become besieged by this shrub, restricting public access and reducing the natural composition of the site. The nectar of R. ponticum is poisonous to man, bees, mice and cats (Abrahams, 1998).
Risk and Impact FactorsTop of page Invasiveness
- Invasive in its native range
- Proved invasive outside its native range
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Highly mobile locally
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Negatively impacts animal health
- Reduced native biodiversity
- Difficult/costly to control
UsesTop of page R. ponticum was used as cover for game animals in the UK and as an ornamental species. Nowadays R. ponticum has no real use in its native or introduced range except for nesting sites for birds and animal species. It continues to be, however, a very popular ornamental species with numerous varieties and cultivars selected and sold for the colourful, abundant and showy flowers.
Uses ListTop of page
- Graft stock
Similarities to Other Species/ConditionsTop of page Common Rhododendron species found in R. ponticum's introduced range and with which it mat be confused include R. annae, R. arboreum, R. campanulatum, R. niveum, R. oreodoxa and R. wallichii, though differentiation is generally possible with available keys.
Prevention and ControlTop of page Cultural Control
Grazing is not a method for control. R. ponticum is unpalatable to most herbivores due to the large amounts of toxic chemicals, particularly 'free' phenols and diterpenes in the leaves (Esen, 2000). The diterpenes, known as grayanotoxins, are not found in all species of Rhododendron but occur in the leaves, flowers and nectar of R. ponticum. Phenols are mostly concentrated in the young tissues, such as young emergent leaves and buds providing a primary defense against herbivores before the tissues have acquired the added deterrent of physical toughness found in older tissues. Young emergent leaf buds have the additional protection of a sticky exudate, which also contains phenols. This also gives protection to the buds against attack by invertebrates.
Heavy machinery with long hydraulic arms is best for digging up the root material and crushing the branches. However, heavy machinery in certain habitats such as ancient woodlands compacts the forest floor causing problems such as increased erosion (Esen, 2000). Operator knowledge of the structural growth of the plant is essential to enable full eradication of the plant without leaving underground suckers. The surface rooting characteristics of R. ponticum should allow for the shrub to be lifted entirely from a site with most of the main rooting structure intact. R. ponticum removal is best suited to autumn and winter in order to make, and take advantage of, a clean uncontaminated seedbed in the spring. Due to the spread of the shrub, a systematic approach is best suited to the removal of the weed at each stage. If R. ponticum is just cut back, this will be followed by vigorous growth from the stumps during the next growing season. An approach of methodical cutting, mechanical removal and burning of root material and stumps is the preferred means to achieve a R. ponticum-free site.
Spraying cut stems with ammonium sulfamate is effective in controlling the growth of R. ponticum though surrounding vegetation may be effected. Glyphosate is commonly used to control R. ponticum in the UK after the bulk of the biomass has been removed by burning or mechanical removal, and triclopyr and imazapyr at differing concentrations have also been used with varying success (Lawrie and Clay, 1989).
Until now, biological control has not been taken into consideration as part of the management strategy for R. ponticum. However, this may offer a potentially simpler, cheaper and safer alternative approach to chemical and mechanical control, or an additional tool in the battle against this weed in the UK. Due to the horticultural importance of the genus Rhododendron, with over 500 spp. currently in cultivation in the UK alone (Mabberley, 1998) the risk associated with the classical approach using coevolved, exotic natural enemies from the native range is considered to be too high (Evans, 2000). However, a number of natural enemies have already been identified in the native range, including a rust fungus from Portugal (Farr et al., 1996). Instead, the proposed strategy is based on the evaluation of natural enemies associated with the weed in the UK, focusing on fungal pathogens for use in an inundative approach. This will involve the mass production and formulation of a selected pathogen and, in the case of R. ponticum, application of such a proposed fungal product or mycoherbicide as a site-selective stump treatment. Potential pathogens include a species of Cryptosporiopsis which was associated with dieback in Berkshire, UK (Shaw, 2003). This strategy has been implemented safely and successfully against woody invasives in the Netherlands, where BioChon, a product based on local strains of the wood-rotting basidiomycete Chondrostereum purpureum, has been marketed for the control of alien Prunus spp. as well as Populus spp. (Jong, 2000). Evaluation of this strategy against similar woody targets is also underway in both Canada and New Zealand.
ReferencesTop of page
Abrahams A, 1998. Rhododendron nectar- poisonous to both bees and man. Scottish Beekeeping, 75:19-20.
Anon., 2003. Dieback hits parks and gardens - the garden. Journal of the Royal Horticultural Society, 128:9.
Ansin R; Terzioglu S, 1994. New botanical variety of Rhododendron ponticum L. (R. ponticum L. subsp. Ponticum var. heterophyllum Ansin var. nova). Turkish Journal of Agriculture and Forestry, 18:137-140.
Bean WJ, 1976. Trees and Shrubs Hardy in the British Isles (8th Edition). London, UK: J. Murray.
Colak AH; Cross JR; Rotherham ID, 1998. Rhododendron ponticum in native and exotic environments, with particular reference to Turkey and the British Isles. Practical Ecology and Conservation, 2:34-41.
Compton SG; Key RS, 1998. Species action plan: Lundy Cabbage (Coincya wrightii) and its associated insects. Peterborough, UK: English Nature.
Cross JR, 1975. Biological flora of the British Isles, Rhododendron ponticum L. Journal of Ecology, 63:345-364.
Doyle G; Klotzli F; Walther GR, 1999. Conference on recent shifts in vegetation boundaries of deciduous forests, especially due to general global warming. Birkhauser Verlag AG, Basel, Switzerland, 237-251.
Elton CS, 1958. The Ecology of Invasions by Animal and Plants. London, UK: Methuen.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Esen D, 2000. Ecology and control of Rhododendron (Rhododendron ponticum L.) in Turkish Eastern Beech (Fagus orientalis Lipsky) forests. Thesis. Virginia Polytechnic Institute and State University.
Gritten RH, 1995. Rhododendron ponticum and some other invasive plants in the Snowdonia National Park. Plant invasions: general aspects and special problems. Workshop held at Kostelec nad Cernymi lesy, Czech Republic, 16-19 September 1993 [edited by Pysek, P.; Prach, K.; Rejmanek, M.; Wade, M.] Amsterdam, Netherlands; SPB Academic Publishing, 213-219
Humphreys DJ; Stodulski JBJ; Stocker JG, 1983. Rhododendron poisoning in goats. Veterinary records, 21:503-504.
Kelly DL, 1981. The native forest vegetation of Killarney southwest Ireland: An ecological account. Journal of Ecology, 69:437-472.
Mabberley DJ, 1998. The Plant Book. Second dition. Cambridge, UK: Cambridge University Press.
Mejias JA; Arroyo J; Ojeda F, 2002. Reproductive ecology of Rhododendron ponticum (Ericaceae) in relict Mediterranean populations. Botanical Journal of the Linnean Society, 140:297-311.
Shaw MW, 1984. Rhododendron ponticum- Ecological reasons for the success of an alien species in Britain and features that may assist in its control. Aspects of Applied Biology, 5:231-239.
Shaw RH, 2003. Biological Control of Weeds in the UK: Opportunities and Challenges. In: Child L, Brock JH, Brundu G, Prach K, Pysek P, Wade, PM, Williamson M, eds. Plant Invasions, Ecological Threats and Management Solutions. Leiden, The Netherlands: Backhuys Publishers.
Terzioglu S; Merev N; Ansin R, 2001. A study on Turkish Rhododendron L. (Ericaceae). Turkish Journal of Agriculture and Forestry, 25:311-317.
USDA-ARS, 2003. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
Distribution MapsTop of page
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