| 1 | | | Arnold Arboretum (USA) |
| 2 | | | Brooklyn Botanic Garden (USA) |
| 3 | | | Crystal Springs Rhododendron Garden (USA) |
| 4 | | | Descanso Gardens (USA) |
| 5 | | | Holden Arboretum (USA) |
| 6 | | | Jenkins Arboretum (USA) |
| 7 | | | Longwood Gardens |
| 8 | | | Magnolia Plantation (USA) |
| 9 | | | Morris Arboretum (USA) |
| 10 | | | Morton Arboretum (USA) |
| 11 | | | New York Botanical Garden (USA) |
| 12 | | | Polly Hill Arboretum |
| 13 | | * | Rhododendron Species Botanical Garden (USA) |
| 14 | | | San Francisco Botanical Garden (USA) |
| 15 | | | Scott Arboretum (USA) |
| 16 | | | Sonoma Botanical Garden (USA) |
| 17 | | | Tyler Arboretum (USA) |
| 18 | | | UBC Botanical Garden (Canada) |
| 19 | | | UC Berkley Botanical Garden (USA) |
| 20 | | | US National Arboretum |
| 21 | | | Washington Park Arboretum (USA) |
| 22 | | | Winterthur (USA) |
