Growing best in wet to mesic soils, blue flag iris is a perennial that prefers full sun to partial shade. Growing to a height of 3 feet, the beautiful blue flowers are in bloom from May-July. There is a noticeable yellow blotch on the bottom sepal of this flower which sets it apart from other members of its genus. Spreading by both seeds and rhizomes, this plant can form large colonies is the highly fertile soil that it thrives in. Seeds are often dispersed by water flow where the seeds can float atop the water.