What you need : Irises are one of the easiest perennials to grow even for novice gardeners. They require at least six hours of direct sunlight in order for them to grow and bloom well. Set plants in a well drained location where water does not tend to stand. Wet feet, produces many problems for the iris grower. If you have these two requirements you are well on your way to becoming an iris grower.
How Irises grow : They grow from thick underground stems called rhizomes (pronounced rye-zome). These rhizomes store food produced by the leaves. The original rhizome grows just beneath the soils surface with many small roots imbedded into the soil. Each year the original rhizome produces new rhizomes. The multiplication will eventually form a clump that should be divided every 3 to 5 years. When a rhizome is removed with one bud or growing point it will produce a large fan of leaves and a flower stalk.
When to plant : Like many perennials irises may be moved any time if proper care is taken. But, the best time to plant or move them is during the dormant period which is from late summer to early fall, usually July and August. Rhizomes need to develop a root system before freezing occurs.
Fertilizing : Bone meal and most fertilizers with low nitrogen are good for iris growth. Apply to soil, using one-half cup per each 5 by 10 foot area or for every 6 - 7 irises before planting. Minimum fertilizing is required on established plants. Soil should not have a high acid content. Lime can be used to sweeten the area where your irises are to be planted.
How to plant : New rhizomes should be planted about 18-24 inches apart to allow for clumping. Dig and loosen your soil, mix in fertilizer and add lime if necessary. Dig a hole and form a mound in the center, set the rhizome on top of the mound, spread the roots around the mound and pull the dirt toward the plant fully covering the roots but leaving the top of the rhizome bare or just barley covered. Firm the soil tightly around the rhizome so the plant will be held firmly in place. Plant rhizomes facing the same direction so they will increase in the same direction.
Watering : As with all new plantings, irises should be watered, soaking the roots. Established plants require little to no watering depending on your growing conditions.
Cultivation and care : Following the steps above you should get a well established plant. To assure a healthy plant that will continue to produce beautiful bloom you have to go one step further. Gardeners should strictly adhere to the old saying, “cleanliness is next to godliness”. Keep your garden free of weeds and grass. This is much easier if you plant your irises in rows rather then beds. A weedy garden is an invitation to trouble. Cultivate shallowly being careful not to damage the roots or rhizome. A pre-emergence can now be applied if you want to use chemicals to help with the cleanliness process. If you are not hybridizing cut the bloom stalks off close to the ground after they have finished blooming. Do not cut the leaves (fans) back as they are required for new growth. Different growers will tell you differently about cutting back the fans in late fall. I cut mine off in the very late fall/early winter time period. Discard all waste from the garden. Do not mulch over the rhizomes as this may produce rotting in wetter climates or seasons.
Separating and transplanting : This should be done one to two months after your irises have bloomed, usually in July and August. This will give the newly planted rhizomes time to form roots before the winter freeze. Iris clumps need dividing every 3 to 5 years to assure maximum growth and bloom. Dig up the rhizomes you want to move, cut off a rhizome with a growing point and follow the same steps as when you planted the original rhizome. All rhizomes that you remove from the original will be exactly the same color as the original rhizome and will never change. This is known as “vegetative propagation”.
