Iris versicolor, commonly known as Northern blue flag, is native to the northern part of the United States and into Canada. The flower stalks stand 2 to 3 feet tall, each with 3 to 5 blue flowers in May and June. The flowers have a prominent yellow blotch and a white area with purple veins at the base of the falls. Northern blue flag will grow well in full sun to part shade and in average soil, but it loves the edge of a pond or stream where it can keep its feet wet. It is closely related to the Southern blue flag iris, Iris virginica.