RHODODENDRON RESEARCH PROJECT Inger and Rh. Arboreum in full bloom on Tinjure Danda, E. Nepal
This project was sponsored by the Norwegian Research Council, and the project leader is Dr. Ole R. Vetaas . It is based at the Botanical Institute at the University of Bergen in collaboration with The Norwegian Arboretum at Milde - Bergen. Collaborators are Prof. Per M. Jørgensen, Director Per H. Salvesen, and Prof. Ram P. Chaudary from Tribhuvan University of Kathmandu, Nepal.
Aims , Information sources , Questions , Target taxa , Illustrations, Human use, Questionnaire, Related links.


Vetaas, O.R. 2000. Comparing species temperature response curves: population density versus second-hand data. Journal of Vegetation Science , 11: 659-666. (Download PDF-FILE)

Vetaas, O.R. 2000. Separation of sub-species along a temperature gradient. Proc. IAVS symposium 1998:28-31.  (download-PDF-file)

Vetaas, O.R. 2002. Realized and potential climate niches: A comparison of four Rhododendron tree species.
Journal of Biogeography , 29: 545-554. (Download-PDF-FILE )




    The present project aims to identify the climatic limits for selected Rhododendron species (see below) found in the Nepalese Himalaya region.
    Rhododendrons are very popular garden plants due to their large, colourful  flowers as well as their large, shiny green leaves. The applied aim is to be able to predict the chances of survival for Nepalese Rhododendron species when they are grown in gardens located in temperate climates. Several theories indicate that certain low temperatures are critical in defining the range of evergreen rhododendron species. At the upper end of the temperature range, water efficiency is relatively more important.
    The long term aim is to develop this knowledge further within a Nepalese institution, which will then provide seeds and/or seedlings for sale, stimulate local economy, and help with reforestation.
    In order to generate information about the climatic limitations of the selected Rhododendron species we depend on information from gardens/arboreta which have these species. If you have any of these species, your collaboration is essential to our research. Please fill in the questionnaire that you find on this page. The results of our research will be published on this page after completion, for your reference.
    Information that you submit will be compared to the data collected in Nepal and an overall picture of the climatic limitations of these species can be outlined.


    Three different data sources are used to develop predictive models for Rhododendron species and sub species:
  • 1. Distribution maps based on Herbaria data and written information can be superimposed on iso-climate maps.
  • 2. The variation in abundance along an elevation gradient (1500 - 4500 m.asl.) with established climate stations.
  • 3. Survival data on Rhododendron species in Botanical gardens and their corresponding climate.
  •     This will facilitate a comparison between the natural climate limits (realized niche) and the limits in cultural condition, where interactions from other organisms is reduced (fundamental niche). How species and their genetically related sub species is distributed along a documented climate gradient provide useful insight in how plant species tackle changes in climate.


        The following questions will be answered by the project for selected Rhododendron species:

  • 1. Which climatic parameters best explain their distribution within their natural habitat i.e. their realized niche?
  • 2. Can these parameters predict their survival outside their natural geographical range?
  • 3. How much different are the climatic limits of related sub species in their natural habitats and in arboreta?

        The following species are part of the current research. The nomenclature follows Chamberlain et al. (1996: The genus Rhododendron - Its classification & Synonymy - RBGE.)

  • 1. Rh. anthopogon ssp. anthopogon
  •                              ssp. hypenathum
  • 2. Rh. lepidotum
  • 3. Rh. arboreum ssp. arboreum
  •                        ssp. cinnamomeum var. cinnamomeum
  •                           ssp. cinnamomeum var. roseum
  • 4. Rh. barbatum
  • 5. Rh. campanulatum ssp. campanulatum
  •                                  ssp. aeruginosum
  • 6. Rh. wallichii
    Rh. lepidotum in bloom in Langtang National Park, C. Nepal
    Rhododendron lepidotum:

    Highly variable low and compact to upright and lean shrub, up to 2m. Flowers open, white, yellow, pink, or purple. Leaves are elliptic, upper surface dark green, lower surface with large brownish scales. Distribution: Kashmir to S.E. Tibet. 2400-4900m.

    (Photographed in  Langtang, Nepal by O.R. Vetaas in 1986.)

    Rh. campanulatum in bloom on Milka Dada, E. Nepal
    Rhododendron campanulatum:

    Rh. campanulatum ssp. campanulatum: Low compact to taller bush/tree, 2-11m. Flowers white to pale rose to lilac. Leaves ca. 9-18cm, upper surface glabrous, lower surface with a continuous indumentum. Distribution: Kashmir-Sikkim. 2900-4100m.
    Rh. campanulatum ssp. aeroginosum: Usually rounded shrub, up to 1.8m. Flowers pink to purple. Leaves 7-10cm, upper surface with a bluish metallic shine, lower surface with a thick and smooth rusty brown indumentum. Distribution: Sikkim-Buthan. 3700-4500m.

    Note:In East Nepal plants are intermediate between ssp. campanulatum and ssp. aeruginosum.

    (Photographed on Milke Danda, E. Nepal by Keith McInturff in spring 1998.)

    Rh. barbatum in bloom on Milke Danda, E. Nepal
    Rhododendron barbatum:
    Upright small tree, 2-9m. Flowers in differing shades of scarlet. Leaves retained for 1-2 years, upper surface deep green, lower surface without hairs or glands. Leaf stem usually with bristles. Distribution: Uttar Pradesh-Buthan. 2400-3700m.

    (Photographed on Milke Danda, E.Nepal by K. McInturff in 1998.)

    A huge Rh. arboreum bloom on Tinjure Danda, E. Nepal

    Rhododendron arboreum ssp. cinnamomeum var. cinnamomeum:
    Flowers usually pink to carmine. Leaves a little smaller than on ssp. arboreum, lower surface with a double layer indumentum, normally fawn in colour. Distribution: E.Nepal-S.Tibet. 2400-4000m.

    (Photographed on Tinjure Danda, E.Nepal by K. McInturff in 1998.)


        In the Himalayas Rhododendron trees are often used for fuel wood. It is an easy wood to cut and the branching trunks make it easier to transport than other species of trees. Large stands of  rhododendrons are found in the same altitudional range as the summer grazing grounds for sheep, goats, cows and yaks. Common species in these areas are Rhododendron arboreum, Rh. barbatum, Rh. campanulatum, Rh. hodgsonii, Rh. ciliatum, and Rh. cinnabarum. Shepherds make use of the rhododendrons as building materials and fuel wood around their summer huts, often clear cutting large stands. This leads to major soil erosion in steep areas.
        The pictures below illustrate two human use practices in Nepal;
    (A): Cutting of rhododendron forest for fuel wood, leaving a single tree of Rhododendron arboreum (photographed in Lukla, C.Nepal by O.R.Vetaas in 1997).
    (B): Grazing in a slightly disturbed Rhododendron arboreum forest (photographed on Chitre Danda, E.Nepal by K. McInturff in 1998)

    An example of clear-cutting of Rh. arboreum in Lukla, C. Nepal (A)Photograph of shepherd with sheep grazing in mature Rh. arboreum forest. (B)


        If you have any of the listed taxa and are interested in helping with this research, I would very much appreciate some information on geography and climate from your garden/arboretum. Please download the questionnaire , answer the questions and mail it as an attachment to Ole.Vetaas@sfu.uib.no


    Deparment of Biology, University of Bergen, Norway.

    The American Rhododendron Society (ARS).

    List of web-sites for ARS-chapters

    CORET: Conifer Research and Training partnership

    Den norske Rhododendron forening.

    Danish Rhododendron society (ARS-chapter).

    The French Rhododendron Society (Société Bretonne du Rhododendron) .


    RESEARCH-SECTION at RBG-Edinburgh site .

    US plant hardiness-zone chart.

    Nepal and Himalaya on the web.


    Responsible Ole R.Vetaas, last updated 06.04.2006