Iris x robusta is a designation for a hybrid of two native American irises, Iris versicolor and Iris virginica. ‘Gerald Darby’ is noted for its violet-blue flowers and dusky purple spring foliage. This plant is touted for its use in sunny sites near ponds, water gardens and moist borders. Purple flowers with yellow-splashed sepals (falls) appeared on purplish-black stems. Flowering began in early June and persisted for about two weeks. One evaluator recommended removing the spent flowers in midsummer.