The Japanese iris is a tender perennial that, unlike most flowering plants, appreciates the feel of wet feet. This Japanese native, known as the Hanashobu, is a water-loving plant that blooms only when its water requirements are met. It requires acidic soils and thrives in most zones from 4 through 8.
Choose a warm, sunny location for your Japanese iris. Select a location that receives at least six to eight hours of direct to partially shaded sunlight each day. The ideal location receives full morning sun with partially shaded afternoon and evening sun. Ensure that the soil is slightly acidic with levels resting between 5.5 and 6.5, as recommended by the Mt. Pleasant Iris Farm. Choose a location near a water bed if possible.
Soak the rhizomes of your Japanese iris before planting. Dig up the planting bed to loosen the soil and remove any compacted areas. Remove any weeds from the soil and make sure the roots of the weeds are also removed. Plant your iris so that the crowns are about 3 inches deep into the soil bed. Plant multiple Japanese iris approximately 20 inches apart.
Irrigate your Japanese iris to maintain a consistently moist soil environment. Water regularly, almost daily, to provide a wet environment in the spring and a moist environment throughout the entire summer. Never allow your Japanese iris to dry out.
Fertilize your heavy feeders in the early spring, just before the first bloom. Select a well-balanced, slow-release fertilizer for acid-loving plants. Distribute the fertilizer evenly throughout the planting bed and irrigate the feed thoroughly into the soil. Keep the fertilizer at least 1 foot away from the crown to prevent root burn and rot.
Protect your Japanese iris' soil moisture and reduce the potential of weed invasion. Apply a 2-inch layer of mulch around the planting bed. Reduce the potential of insect invasion by spraying your iris with an annual insecticide treatment.