Not adequately established: Some iris cultivars need a year or more to fully establish in their new locations before blooming. If you relocate them frequently, they may never become well enough established to bloom. Plant irises far enough apart to allow for several years' growth before requiring division.
Inadequate sun: Bearded irises need at least 6 hrs of direct sun a day to bloom well.
Nutrient deficiencies: Consider having a soil test run to make sure your soil provides all necessary plant nutrients in appropriate amounts and fertilize according to the recommendations returned with the soil analysis. Soil that has been growing irises for many years without amendments or fertilization is probably nutritionally depleted. Avoid high-nitrogen fertilizers. If bearded irises are fed high-nitrogen fertilizers, they may grow lush foliage with little or no bloom.
Inappropriate watering: Bearded irises might not bloom well if they experience periods of extended drought, though the plants themselves are quite drought-tolerant. Conversely, bearded irises that are overwatered are often susceptible to bacterial soft rot and fungal leaf spot infections. If you provide supplemental water, water deeply no more than once a week. Soaker hoses are preferable to overhead watering to avoid spreading leaf diseases from plant to plant.
Planted too deeply: Bearded iris rhizomes should be planted so the tops of the rhizomes are at or slightly below the soil surface. If planted too deeply, bearded irises will grow leaves but may not flower. Be careful, also, not to allow mulch to cover the rhizomes. Make sure any mulch is pushed away from the rhizomes.
Overcrowding: Overcrowded clumps often quit blooming until they are divided, OR irises closely planted with other plants may not bloom well (or at all) if they are struggling to compete for sunlight, water, and soil nutrients.
Weeds: There are certain weeds and grasses that are so aggressive they can inhibit the performance or even survival of plants they invade (Canada thistle being one of them). Keep the weeds and grasses away from your irises.
Ill health: Irises that are diseased or under insect attack may not be able to bloom until the problem is eliminated.
Late freezes: Killing freezes that are severe enough to damage iris foliage within six to eight weeks prior to normal bloom can abort developing stalks even if the stalks are not yet showing above the foliage.
Immature rhizome: Rhizomes will not bloom until they are mature. If you have planted smaller rzs, you probably need only wait for them to grow a bit before they'll bloom.
Irregular bloomer: All irises are not created equal. While some irises may bloom very regularly in your garden once established, others may never do any better than blooming once every several years ... or perhaps never blooming at all. The same cultivars that bloom beautifully and reliably for a neighbor down the road or a friend across the country may do nothing more than sulk in your own garden. The only way to discover which irises will perform best for you is to keep trying different cultivars, growing them properly, and replacing those that don't meet expectations within 2-3 years after planting.
Still have questions? Join us on the Iris forum where you'll find friendly, helpful iris lovers!
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