Rhododendron 'Creekside', which is a natural hybrid of Rhododendron arborescens, has been determined to be a diploid 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.
Rhododendron 'Creekside' may, also, contain Rhododendron viscosum. Rhododendron 'Creekside' is sometimes called "Running Arborescens".
Summary of Ploidy Levels
Diploid Rhododendron arborescens,
Diploid Rhododendron viscosum,
Source: John and Sally Perkins
John and Sally Perkins