Most iris, especially bearded iris, will grow best with full sun for at least 6 to 8 hours a day. In very hot areas though, some shade in the afternoon will help keep flower colors from fading in the heat. Iris should be planted in an area with good air circulation to help prevent disease problems.

Most iris need very well-drained soil. Japanese and Louisiana iris will grow in wet soil. If your soil is not ideal you can amend it with organic matter and build raised beds for better drainage. Do not use manure unless it is very well-composted (aged for at least one year). Manure can encourage iris soft rot. Bearded iris prefer slightly alkaline soil. Many of the beardless iris like a more acid soil. It is a good idea to test your soil and amend the soil before planting a new iris bed.

Fertilize a new iris bed when preparing the soil before planting with a complete fertilizer low in nitrogen and high in phosphorus and potassium. Follow soil test recommendations for best results. In the absence of test results apply 1 pound of 5-10-10 per 100 square feet. Work the fertilizer into the soil and let the bed settle before planting.

When feeding established iris, do not let fertilizer touch the rhizomes. It is better to underfeed than to overfeed bearded iris. Reblooming varieties, however, are more likely to rebloom with supplemental food and water after spring bloom.

Remove old blooms and stalks promptly after flowering to allow the plant to devote its energy to growth rather than seed. Removing old blooms and stalks also encourages repeat flowering on reblooming iris.

The best time to plant bearded iris is July through September, or October near the coast. This will allow them to become well-established before winter. Japanese, Louisiana and Siberian iris can be transplanted during the summer and early fall. Container-grown iris can be planted in the spring.

Bearded iris are grown from a fleshy, bulblike stem called a rhizome that grows horizontally just below the soil surface. Plant iris with the rhizome high in the soil, and the roots well-anchored. Dig two trenches with a ridge between them, place the rhizome on the ridge and spread the roots carefully in the trenches. Then fill the trenches with soil, letting the top surface of the rhizome be just barely beneath the surface of the soil. In heavy clay soils the rhizome should be planted higher so that up to half of the rhizome is exposed above soil level. Firm the soil well and water thoroughly.

After three to five years, iris generally become crowded and should be divided.