Rhododendron "Speciosum Yellow #3" 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.
Clearly Rhododendron "Speciosum Yellow #3" is not straight Rhododendron flammeun.
Summary of Ploidy Levels
Diploid Rhododendron flammeun,
Tetraploid "Speciosum Yellow #3"
Source: Rarefind Nursery
John and Sally Perkins