Rhododendron 'Earl's Gold', which is a Earl Sommerville introduction documented as Rhododendron austrinum or austrinum hybrid, 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
Triploid 'Evening Sun',
Tetraploid Rhododendron austrinum,
Tetraploid 'Earl's Gold',
Tetraploid 'Sommerville Sunrise'
Source: Planview Nursery
John and Sally Perkins
