Rhododendron 'Nancy Evans', which is a Ned Brockenbrough hybrid documented as 'Hotei' x 'Lem's Cameo', has been determined to be a diploid 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.
This Coimbra based research team also determined that 'Hotei' and 'Lem's Cameo' are diploids.
Rhododendron 'Nancy Evans' is seed fertile but pollen sterile.
'Nancy Evans' is the seed parent of 'Horizon Monarch', which was determined to be a tetraploid using flow cytometry by Dr. Thomas Ranney, J.R. Jones, and Nathan Lynch. This indicates that 'Nancy Evans' may occasionally throw unreduced gametes.
Summary of Ploidy Levels
Diploid 'Hotei',
Diploid 'Lem's Cameo',
Diploid 'Nancy Evans',
Tetraploid 'Horizon Monarch'
Source: Whitney Nursery
John and Sally Perkins