Are Irises bi-annual? - Knowledgebase Question

Hillsdale, Ne
Question by n2mfd
April 21, 2010
I have had Irises for about 10 years or so, but they seem to be Bi-annual. Is this correct or is there something I can do for them. The alternate years I still get leaves, but no flowers.... zone 6-full sun

Answer from NGA
April 21, 2010


Irises should bloom every year. If yours aren't, they may be overcrowded and competing for moisture and nutrients, or they may not be getting enough sunshine or being fed enough.

Iris beds should be dug and divided about every 4 years and the healthiest parts of the rhizomes should be replanted. I'd dig the irises, amend the soil with compost or other organic matter, then replant - giving each rhizome 6-8 inches of space. Set the rhizomes just barely below the soil surface. Water them well and then side-dress with a 5-10-10 fertilizer (or equivalent). They should bloom for you next year and every year after that.

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