Why Is My Iris Not Blooming?

An iris should blooms for three to four weeks in the spring.

The family Iridaceae and the genus Iris contain more than 200 species and subspecies. Irises grow in many colors, but the most common are shades of purple, white, yellow and blue. They grow from bulbs or rhizomes. The iris is a hardy plant requiring little care. When an iris does not bloom, the problem is often easy to correct.

Sunlight

Irises require full sun to bloom. Without enough light, the iris will not have the energy to bloom. If the iris is more than 2 years old and has never bloomed, transplant it to a sunnier spot in late summer. If the iris is an immature plant, give it one more year to develop a strong root system. If it does not bloom the following spring, transplant it.

Fertilizer

The iris does not respond well to nitrogen-rich fertilizers. Fertilize the iris in early spring and again in the summer with a low-nitrogen fertilizer. If you used a combination higher than 5-10-10 or 6-10-10, do not add any more. Begin the following spring with a small amount of an appropriate fertilizer, and your iris should bloom in the summer. If you have a rhizome iris, do not allow the fertilizer to touch the rhizomes that are above the ground.

Crowding

When an iris grows too large, it has difficulty blooming. Dividing iris clumps every 3 to 4 years avoids overcrowding. In late summer, remove the iris clump from the ground. Carefully separate the iris into smaller clumps, preferably of just one to two rhizomes or bulbs, and replant each smaller clump in different locations.

Planting Depth

Gardeners often plant iris rhizomes too deeply. The rhizome top should be visible when properly planted. Dig up the clump in late summer and carefully loosen the soil around the rhizomes and roots. Fill in the hole to the proper depth with soil and replant the iris. Partially bury the rhizome, leaving the top exposed and position the roots downward in the soil.

References

• Schreiner's Iris Gardens: How to Grow and Care for Iris
• North Dakota State University Extension; Questions On: Iris; Ron Smith
• Daily Press; Q&A: Why Won't My Iris Bloom?; Kathy Mullekom; April 3, 2007