Rhododendron 'Gartendirektoer Rieger' features bell-shaped flowers measuring 2¾" to 4" wide, predominantly white with a subtle pink hue and striking deep purplish-red spotting on the dorsal side. These blossoms are presented in open clusters containing 4 to 9 flowers. The plant has rounded, slightly curved leaves with yellow-green petioles and maintains an upright growth habit. It thrives in partial sun, requiring ample light for abundant flowering while favoring filtered sunlight for optimal leaf development. It withstands cold temperatures down to -10°F (-23°C).