You’ve found the perfect place for all your questions about growing, showing and loving irises. The American Iris Society is an international organization of gardeners dedicated to advancing interest in and knowledge of irises. We want to help you, the gardening public, to grow and love irises.
Please wander around our site and see the wonderful variety of the diverse iris family. We have information on irises for every garden condition: dry, wet, sun, shade, clay, sand, or gravel. Irises can be added to almost any garden. There are irises in every height from 2 inches to 6 feet. There are irises that bloom with the crocus in early spring and some that bloom in high summer. Some even bloom in the autumn. Come and explore the possibilities.
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Iris are generally discussed in two groups: Bearded and Beardless.
Bearded have a fuzzy beard on the fall (the bloom part that hangs down). Beardless do no have this. Their cultural requirements are different although both can be easily integrated into your existing garden.
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.
To plant your bearded irises, choose a sunny spot in well drained soil. Prepare the 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. If possible, this should be done 2 to 3 weeks before you are ready to plant. A well prepared bed will result in better growth and more bloom. Don’t starve your irises or make them compete with nearby grass or weeds for food and water. Many gardeners, iris and otherwise, have soil analyses made of their garden soil, then add the fertilizer of the kind and quantity the tests show the soil needs.
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. An easy way to achieve this is to dig two trenches with a ridge between them, place the rhizome on the ridge and spread the roots carefully in the trenches. Be sure to firm the soil tightly and allow enough for settling to keep the rhizome above any possible standing water. Then fill the trenches with soil, letting the top surface of the rhizome be just barely beneath the surface of the soil.
If you have several plants, plant them at least a foot and a half apart, “facing” the same way. The rhizomes will then increase in the same direction, without crowding each other too soon.
From the new parts of the rhizome, new bloom stalks will come up in later years and the flowers will be exactly as the original flower. This is called “vegetative propagation”.
In about 2 or 3 years, the new rhizomes will begin to crowd each other and you will want to divide the plant, cutting the newer parts of the rhizome free from the old, which may then be discarded. Unlike the other bearded irises, arils need to be transplanted annually.
You will have so many new rhizomes that you will share them with your friends. Perhaps you received your first rhizomes from a friend. When digging, keep all plants carefully labeled with their names, for sure identification. It is wise to keep diagrams of your planting area to double check individual labels on the plants.
This digging and separating is best done between one and two months after bloom season, usually in July or August. Soon after this the irises grow roots which help to hold the plant firmly during the winter in areas where freezing and thawing can result in heaving the rhizome out of the ground. If you live in this type of climate, a mulch of salt hay can be very beneficial.
Culture of the beardless irises differs somewhat from culture of the bearded irises. They should be transplanted in the fall or in early spring. The roots should never be allowed to dry out while they are out of the ground and they should be watered heavily after transplanting. They should be set slightly deeper than the tall bearded.
Japanese iris should be planted in a distinct “depression” in heavy soil to assist in supplying moisture to the plant.
Siberians and the Pacific Coast Natives can tolerate light shade but the Spurias, Japanese and Louisianas demand full sun.
Louisianas and Japanese require moist conditions during the summer months while the Pacific Coast Natives enjoy a very low humidity and dry soil no matter how hot it may get. All, except Louisianas, should be planted in a permanent spot where they can remain for many years as they resent being disturbed. Louisianas are strong and quick growers and therefore, should be tended to every few years. All are heavy feeders and need to be fertilized regularly.
Contemporary Views by Perry Dyer
New AIS members receive a $25 voucher at participating nurseries. Details of the voucher program can be found here
New AIS members also receive a copy of the AIS publication Basic Iris Culture, an informative booklet that provides useful guidelines for successfully growing irises.
AIS members also receive a quarterly publication, IRISES The Bulletin of the American Iris
Society. Each issue of IRISES provides approximately 65 pages of fresh information on iris culture, an array of color photographs of both old and new irises, and an advertising directory of commercial iris growers located throughout the United States.
As an AIS member you will be able to learn about and to participate in a wide range of activities and programs:
For more information on membership please see AIS Membership Information
The AIS has associations with other organizations that have interests in particular types of irises. AIS charters these organizations as Sections. For membership information about AIS Sections
Cooperating societies are other organizations that have primary purposes that are consistent with those of AIS. For membership information about AIS recognized Cooperating Societies