
I'm on vacation, so only a short written accompaniment today. – Daniel
The Magnolia Society has an excellent site that includes a checklist of magnolia cultivars and an extensive section of the site by Richard Figlar (who I corresponded with on this BPotD entry) on the classification of magnolias.





Magnolia campbellii subsp. campbellii 'Ethel Hillier' - Z8 - RHS Index of Garden Plants, Griffiths
Magnolia campbellii subsp. campbellii 'Ethel Hillier' - 'A vigorous, hardy form' - Hillier Manual of Trees & Shrubs, 2003
Mirrors that other famous and variable Himalayan flowering tree, Rhododendron arboreum in showing at least a partial tendency for those with white flowers to be the most hardy and those at the other end of the spectrum, with blood red (rhododendron) or purple (magnolia) flowers to be least hardy. Pink forms may often fall between the two flower color extremes in their cold tolerance.