Rhododendron 'Daviesii', which is a 1840 Isaac Davies hybrid often documented as Rhododendron viscosum X Rhododendron molle, has been determined to be a triploid using flow cytometry by
Dr. João Loureiro, Dr. Silvia Castro, José Cerca, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal.
Rhododendron 'Daviesii' is documented to be the seed parent of 'Moorgold', which is a Schmalscheidt hybrid. John Migas has indicated that 'Daviesii' sets viable seed.
Davies' notes indicate that 'Daviesii' was produced using "A. sinesis crossed a hardy white azaleas."
Rhododendron 'Viscosepalum', which is often documented to be Rhododendron molle X Rhododendron viscosum, has been determined to be a tetraploid.
The flow cytometry ploidy results for 'Daviesii' and 'Viscosepalum' indicate the pollen parent may have been the tetraploid Rhododendron atlanticum rather than the diploid Rhododendron viscosum. The normal bloom times for Rhododendron molle and Rhododendron atlanticum overlay whereas this is not the case for Rhododendron molle and Rhododendron viscosum. Rhododendron viscosum and Rhododendron atlanticum are known to colocate in the wild.
'Viscosepalum' and 'Daviesii' are sometimes confused in commercial settings.
Rhododendron 'Daviesii' was also determined to be a triploid using flow cytometry by Tom Eeckhaut.
Plants labeled Rhododendron 'Daviesii' have also tested as tetraploid and pentaploid.
Summary of Ploidy Levels
Diploid Rhododendron molle,
Diploid Rhododendron viscosum,
Triploid 'Graf von Meran',
Triploid 'Daviesii',
Triploid 'Gloria Mundi',
Triploid 'Josephine Klinger',
Tetraploid Rhododendron atlanticum,
Tetraploid 'Viscosepalum'
Source: Greer Gardens
Source: Whitney Nursery
Source: Azaleatuin
John and Sally Perkins
