Rhododendron 'Norma', which is a 1888 L. de Smet Rustica hybrid, 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.
Rustica hybrids are a mixture of double flowered Ghents hybrids and the Mollis hybrids. The Mollis hybrids contain the diploid species Rhododendron molle. To date all Ghent hybrids (except one)including the doubles have tested as triploid or tetraploid.
Rhododendron 'Norma' was also determined to be a triploid using flow cytometry by Tom Eeckhaut.
Summary of Ploidy Levels
Diploid Rhododendron molle,
Triploid 'Norma'
Source: Arnold Arboretum Accession Number: 142-44
Source: Azaleatuin
John and Sally Perkins
