Dexter’s breeding goals were hardiness, clear bright colors, fragrance and big blossoms. His plants are typically hardy to -10 but flower buds are hardy to about 5 degrees above. At the height of his hybridizing, Dexter created over 10,000 rhododendron seedlings a year.
In the years 1945-1953, a rhododendron study group led by John Wister, then Director of the Scott Horticultural Foundation of Swarthmore College, Swarthmore, PA, began the search for plants that had left the former Dexter Estate. Over those years this group studied and collected plants from Longwood Gardens, the U.S. National Arboretum, Winterthur, John J. Tyler Arboretum, Morris Arboretum and Planting Fields Arboretum, as well as several other estates and gardens. The plants were propagated and eventually (1970-1972) brought to Heritage Museums & Gardens where they were evaluated and a selection of Dexter’s cultivars were named.
Heritage’s most notable rhododendrons include:
- ‘Scintillation’- with a subtle pink color with shades of yellow, ‘Scintillation’ is considered to be the best of the plants created by Dexter. It can grow up to 8’ tall and 8’ wide in 20 years, has a pleasant fragrance, and when closely examined, it’s flower clusters are 8-10” across and made up of 20+ funnel-shaped clear pink blossoms with freckling on the upper side.
- ‘Yellow Gate’- hybridized by Dexter Estate Superintendent J.C. Cowles in the 1960s, the ‘Yellow Gate’ rhododendron begins its bloom with coral pink buds that open into vibrant yellow petals.
- ‘Dexter’s Orange’ – an original Dexter hybrid that boasts wonderful pink flowers that appear orange from a distance. They have the added bonus of being wonderfully fragrant.
- ‘Dexter’s Spice’ – boasts one of the largest white flower clusters of any rhododendron. This cultivar is known for its fragrant flowers that has a distinctive spicy fragrance.
- ‘Eben Jordan’- hybridized by Dexter Estate Superintendent J.C. Cowles in the 1960s, Eben Jordan is known for its beautiful magenta color with a white blush and deep magenta spots.