Planting and Growing Irises:
Irises are among the easiest of perennials to grow, and they give an abundance of beauty with minimum care. The iris has a thick fleshy root called a “rhizome” (pronounced rye-zome) about like a tough potato in texture. When you buy a new iris, you will probably receive a rhizome with clipped roots and leaves. It can remain out of the ground for a week or two without serious harm, but the sooner it is planted, the better. It helps if you soak the rhizome overnight in water just before you plant.
To plant your irises, choose a sunny spot in well drained soil. Prepare soil well by spading or turning over the soil with a garden fork to a depth of at least 10 inches. Spread fertilizer and work it into the top of the soil. A well prepared bed will result in better growth and more bloom. The soil should be light. If it is clay soil, add very coarse sand and humus. Bone meal and a good garden fertilizer, low in nitrogen, are good for irises, but manure should be used only after it has aged for about a year. Otherwise, it may cause rot. The roots must be buried firmly to hold the plant in place, but the rhizome should be near the surface.