If you have a soggy area around your place that you don’t know what to do with, have I got a plant for you? However if you aren’t willing to water during dry spells, stop reading right now and go off to another section of the Quad Cities Daily as this plant is not very forgiving.
Japanese iris (Iris ensata) has the largest flowers of all irises, anywhere from four to eight inches across. They have lovely large flat either single, double and peony-type forms, in various colors and patterns. Singles have three falls (the lower flower petals of iris), doubles have six and peony-type has nine or more. Bloom time is from late June to July about a month after the tall bearded and Siberian iris
Japanese iris leaves are taller and thinner than bearded iris leaves and similar to Siberian iris. A good way to distinguish Japanese iris is by the rib that runs lengthwise down the leaves.
They require full sun, a rich, acidic soil and ample water. They prefer a rich soil containing organic matter, which helps in water retention as well as adding nutrients. Japanese irises are heavy feeders. Use an azalea-type fertilizer in the spring, just after bloom. I like to use cotton seed meal. You can get a 50 pound bag at the Co-op and use left over’s on your blueberries and azaleas. Keep the pH between 5.0 and 6.5. Do not use lime as it raises the pH and will kill the plants eventually. Use a biweekly application of a water soluble acid fertilizer such as Miracid on the leaves and around weak plants. Japanese are generally vigorous growers and a spacing of three or four feet between plants is needed. Two to three inches of mulch will help hold in water and reduce weeds. Two to three year old clumps usually have the best blooms. They grow in zones 4 through 9. The Shoals area and the top half of Alabama is in zone 7 on the new USDA plant hardiness map. Zone 7 is smack dab in the middle of their comfort zone.
I have mine in a low area that gets the runoff from the down spout drain of the barn as well as run off from my Mom’s yard. They really like water. Lack of water will stunt the plants and produce miniature blooms. A good place to plant them is near a pond or stream.
When planting Japanese iris allow plenty of room for to spread. They should be planted two to three inches deep in a depression which will allow it to catch water. Mulch well and do not let the plant dry out. New roots will grow above the old roots and after three or four years the roots will start coming out of the ground, a signal that it’s time to divide. Another sign that division is needed is a clump that has formed a solid ring with a bare center. Best time to divide is in the spring. After the plants have been divided, trim the leaves to a height of four to six inches. Do no plant in an area where other Japanese iris have grown as the plants will be stunted and eventually die, unless it is an area that has lots of water leaching through it such as soil under a downspout or by the side of a stream. They can be replanted in pots if fresh potting soil is used and the old soil discarded. Apparently they secrete some sort of toxin into the soil while growing that is toxic to other iris. When replanting in an area which contained Japanese iris, plant something else beside iris.
For overwintering, remove and destroy old foliage after the first hard frost which may contain borer eggs or thrips.
Check out my GRIT magazine blog post: