Rhododendron 'Cynthia', which is a 1856 Standish and Noble hybrid documented as R. catawbiense x R. griffithianum, has been determined to be a triploid 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.
'Cynthia' is the pollen parent of 'Countess of Derby'. M. Stockman used 'Cynthia' as a seed or pollen parent in several of his crosses.
'Countess of Derby', which has 'Pink Pearl' and 'Cynthia' as parents and 'Broughtonii' as an ancestor, is a cross between 2 fertile triploids.
Summary of Ploidy Levels
Triploid 'Broughtonii',
Triploid 'Cynthia',
Tetraploid 'Countess of Derby'
Source: Whitney Nursery
John and Sally Perkins
