Bearded irises are among the easiest perennials to grow. With reasonable care they will produce beautiful blossoms year after year.
For best results, plant iris rhizomes in July or August in the Prescott, Arizona area. The roots of newly planted iris must be well established before the end of the growing season. Roots take 3-4 weeks to develop so planting a month before the first frost is essential.
Iris require at least a half-day of sun, but bloom best in full sun. Select an area with good drainage.
Irises will thrive in most well drained soils. In clay soils, gypsum is an excellent soil conditioner. A good procedure is to dig a generous amount of compost into the soil.
Irises should be planted so the tops of the rhizomes are visible. Spread the roots and tamp soil firmly to remove air pockets and to anchor the rhizomes. Water well at planting time.
Planting rhizomes 16 to 24 inches apart is the norm. Close planting results in instant color but makes dividing clumps a more frequent necessity.
Newly planted rhizomes need moisture so their root systems develop. Once established, water deeply once a week. Deep watering is better than frequent shallow watering. Over watering of iris can result in rhizome rot. Soil should be moist but not remain wet.
The soil type for your area will determine your fertilizer needs. Superphosphate, alfalfa pellet (without salt), bone meal, or 6-10-10 fertilizer are recommended. Avoid anything high in nitrogen as it encourages soft rot. A light application in early spring and again a month after bloom is encouraged. Place fertilizer around rhizomes, not directly on them.
When irises become crowed, usually 3 to 4 years, bloom will decline. At this time, old clumps may be thinned by removing several divisions and leaving a portion of the clump in the ground. A better practice is to remove the entire clump, replenish the soil, break the clump apart and replant a few large rhizomes.
It is extremely important to keep your iris beds free of weeds and fallen leaves so the rhizomes may bask in the sun. Space plants so there is good air circulation to help prevent diseases. Remove bloom stalks as soon as bloom season is over. This prevents contamination of your named varieties by chance bee crosses.
Visit the American Iris Society (AIS) for a list of commercial growers or look in the back section of any AIS Bulletin. The AIS web site is a good source for iris news, links to the AIS Sections (specialty groups), regions and local iris clubs. Most commercial growers have web sites where their irises may be viewed before purchase.
For specific questions about growing iris and more detailed information, come to the PAIS club meetings, the May iris show or the summer rhizomes sales.