Several cultivars of iris thrive when planted in bogs or shallow water that covers their crown, such as pseudacorus and laevigata. They bring height, sturdy green foliage and colorful flowers to the edge of ponds, streams, pools and lakes. Plant water iris directly into shoreline soil or in containers set below the water's surface, depending on the site requirements and your preferences. As water iris are known to be invasive and are in fact restricted species in some regions, container planting provides some control over the spread of the plants.
Plant water iris in soil-filled nursery pots several inches larger than the plant root ball. Layer 1/2 inch of gravel or stones in the bottom of the pot to prevent soil seeping out and to weigh down the pot. Set the pot into the water on a stable surface of soil, a stone slab, bricks or other riser material. Ensure that the crown of the iris plant is between 1-3 inches under the surface of the water but no deeper.
Plant water iris rhizomes directly into the soil of the water bed so that the soil comes to just above the rhizome and to the crown of the plant. Bury the plant in a spot where the surrounding water consistently comes no higher than 3 inches over the crown of the plant.
Layer an inch or so of gravel or small stones over the soil, surrounding the iris roots to hold the soil in place under water and anchor the pot in an upright position. Surround, but do not cover over, the crown of the plant with the stones or gravel.