Rhododendron maximum 'Summer Joy', which is a Augie Kehr chemically treated Rhododendron maximum has been determined to be a tetraploid 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.
Summary of Ploidy Levels
Diploid Rhododendron maximum,
Tetraploid Rhododendron maximum 'Summer Joy'
Source: Rarefind Nursery
John and Sally Perkins
