Rhododendron 'Siskin', which is a Waterer Knaphill documented as a crossed between Rhododendron luteum and Rhododendron molle, has been determined to be a tetraploid using flow cytometry by
Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, 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.
Summary of Ploidy Levels
Diploid Rhododendron molle,
Tetraploid Rhododendron luteum,
Tetraploid 'Siskin'
Source: Planeview Nursery
John and Sally Perkins
