Growing Irises

 Irises are among the hardiest of all perennials; they will survive and even bloom under harsh conditions from zone 3 to zone 9. Mid May through early June, just as the Tulips and Daffodils are finishing, the Irises burst into color. Irises are not what they used to be when our grandparents referred to them as ‘flags.’ Hybridizing has made the blooms larger, added ruffles and given them an amazing array of color. Twice blooming or re-blooming varieties have also been introduced.

 Irises grow from Rhizomes, which are knobby fleshy roots. They are not real picky about the soil they grow in, but prefer rich sandy loam. Irises like to be well watered, but once established they are also somewhat drought resistant. They don’t require a lot of feeding but do appreciate a light application of a balanced fertilizer; low nitrogen, such as 16-16-8 or 14-14-14. This should be applied in early spring.

 In early spring, dead foliage from last year’s growth should be raked and/or pulled away. By late April and early May, the rhizomes come alive and the plants grow quickly. Depending on springtime temperatures, by late May they are blooming at their peak.

 Irises also have a reputation for going from gorgeous to ugly. If you subscribe to that idea, it happens in June. June is when the flowers are done and shriveled on the stem. This can be unsightly, but if you cut and clear away the spent flower stem, the remaining sword shaped leaves are quite attractive.

 Mid July begins the ideal time to separate Irises. They need to be separated about every third year to maintain their vitality. The rhizomes are continually growing and can soon become a clump of matted roots competing for space. If not divided periodically, the clump will eventually stop blooming.


  • Dig deep enough so that you don't cut the roots that extend downward from the rhizome              
  • Cut away the individual rhizomes supporting 4 to 6 leaves in a fan.
  • Cut the leaves down to a six inch fan above the roots        
  • Turn and loosen the soil in the new location
  • Dig a hole deep enough that the roots can hang down without bunching below the rhizome  
  • Cover the roots and press the soil firmly leaving the upper half of the rhizome exposed.   
  • Water the new planting well to make sure there are no air pockets around the roots.
  • Some new plantings may not bloom the following spring, but most will if they have time to establish themselves before winter.

If you have the space, plant Irises in rows about three feet apart in every direction. If your space is limited, plant them toward the middle or back of your flower bed so that when they have bloomed and the flower stem is removed, they can be a dramatic backdrop for your smaller and colorful annuals.

The Iris growers I know enjoy sharing their success and their expertise. Trading new plants is part of the satisfaction and pleasure. Get to know the enthusiasts and you'll soon be one yourself. 

 The following links are just a few of the many sources for Irises:

K. Van Bourgondien 


Michigan Bulb 

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