Q. How do I encourage my bearded iris to produce more flowers?
When bearded iris (Iris germanica) has finished flowering, the flower stalk only should be cut down to the base. This will help the rhizomes to grow and thus provide better flowers for next year. Some irises are designated as “re-blooming” and may re-flower in the same season, but this is not reliable.
Iris will produce more blooms if a few simple rules are followed. First, irises need lots of sun (at least 6 hours a day) to flower well. Also, they need well-drained soil. They should be watered only in very dry periods; over-watering iris is a common mistake. Another important rule is that the rhizomes should not be planted too deeply. The tops of the rhizomes should be visible through the soil. Finally, irises should not be fertilized with preparations high in nitrogen; superphosphate or a 5-10-10 fertilizer is good.
Every 3-4 years, irises will become too crowded, causing bloom to decline. Thin them by removing several divisions and leaving a portion of the clump in the ground. Even better, remove the entire clump, replenish the soil, and replant a few large rhizomes.
The American Iris Society website provides good advice on growing irises.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service