The first director of the Scott Arboretum, John C. Wister, was a passionate rhododendron grower and hybridizer. Largely due to his efforts, over 350 different rhododendron and azalea cultivars now grow at the Arboretum. While they can be seen across the Arboretum, the rhododendron collection is concentrated by the Scott Outdoor Amphitheater in the Crum Woods. The plants thrive here in the understory of the massive oak, ash, and tulip trees. Spring is the season to observe these plants in flower as their colorful blossoms light up the forest.