Royal Horticultural Society - Plants: Rhododendrons

Rhododendron 'Donvale Cherry' - Photograph copyright RHS With more than 850 species and 25,000 cultivars, rhododendrons provide great diversity for the garden. Whether ground-hugging alpines or forest tree species, exotic and tender vireyas or the most cold-resilient hardy hybrids, there are rhododendrons to suit most lime-free gardens. Even this traditional restriction to acid soils is being challenged by plant breeders selecting for lime tolerance. An experiment examining these lime-tolerant rhododendrons is underway at RHS Garden Wisley.

A list of rhododendrons grown in the British Isles up to 1850

Information on rhododendron bud blast and non-flowering is available in the Advice section.

Rhododendrons with Camellias and Magnolias 2007

This annual collection of illustrated articles for rhododendron, camellia and magnolia enthusiasts is contributed to by international experts, both professional and amateur, and covers a wide range of botanical, horticultural and historical subjects involving plants, places and people.

Among other gems for 2008, Richard Figlar introduces the ‘new’ evergreen magnolia species, Mark Flanagan retraces Ernest Henry Wilson’s steps in China, Kenneth Cox shares his thoughts on breeding evergreen azaleas for the 21st century and two head gardeners describe the challenges they face in maintaining important collections of these three genera.

Paperback 114 pages. ISBN 9781902896854, Priced £11.95
Available from RHS Enterprises; tel: 0845 260 4505; e-mail: mailorder@rhs.org.uk

The RHS Rhododendron, Camellia and Magnolia Group

Founded in 1945, this group is for all RHS Members who share an interest in rhododendrons, camellias, magnolias and associated plants. View the website.

The RHS International Rhododendron Register

The Register maintains a record of all registered cultivar names in the genus. Anyone raising or naming new cultivars is encouraged to register them. This is a free service that helps prevent different plants sharing the same name. The Register also keeps detailed information on plant characteristics, date, parentage, raiser and introducer of rhododendron cultivars.
Registration of Rhododendron cultivar names

The RHS Rhododendron and Camellia Committee

One of the many Floral Committees that provide a source of expertise to the RHS on a particular plant group. For an insight into what goes on behind the scenes of the specialist RHS Floral Committees see the article by Nigel Colborn in The Garden (Jan. 2000) 125(1):33-35. The Committee assesses potential candidates for the prestigious Award of Garden Merit and judges plants put forward for RHS Exhibition Awards. Representatives from the Committee also judge RHS Trials and Ornamental Plant Competitions. Contact the Committee Secretary for further details.

RHS Exhibition Awards

Exhibition Awards are given to plants with show-bench quality. Rhododendrons are usually put before the Committee in a vase. Three awards for plants are available, the highest being the First Class Certificate (FCC), followed by the Award of Merit (AM) and the Certificate of Preliminary Commendation (PC). Anyone can put plants forward for such Awards on specified dates when the Committee meets, either at the monthly RHS London Flower Shows (from January to June) or the Chelsea Flower Show. Contact the Committee Secretary for further details.

Rhododendron competitions

Ornamental Plant Competitions are held at the monthly RHS London Flower Shows. Anyone can enter and competitions specifically for rhododendrons are held in March and April. Contact the London Flower Show Manager for further details

RHS trials

Current RHS trials include one of Rhododendron yakushimanum hybrids. The 133 entries in the Trial reflects the great interest in these hybrids, especially as plants for the small garden. Open days are held at regular times during the flowering season.
The Award of Garden Merit

Rhododendron Societies

American Rhododendron Society
Scottish Rhododendron Society

Rhododendrons