trim iris root - Knowledgebase Question

Bossier City, LA
Question by francescharl
May 6, 2012
Although iris does not have a bulb, this was as close as I could identify my question. My plants have bloomed this year, and I wish to dig and divide. I understand I should wait until the follage has died back, but unable to do so this year...(need to separate). Please tell me how much I should trim and discard from the tubular(?)...some of them have dead or diseased looking root, and others are still looking like viable. Thank you. Frances Charles

Answer from NGA
May 6, 2012


I agree with you - sometimes the category choice is limited or doesn't seem to apply. But, we got your question and we're happy to answer it. I don't think there's any hard and fast rule about waiting until the foliage dies down before digging and dividing irises. It is a good idea to dig up rhizomatous irises every 4-5 years so you can separate out the weak and diseased ones. Then at the same time you can amend the soil a bit. They'll love you for it! After blooming lift the entire clump with a spade and separate it into small clusters of rhizomes (this is what the roots are called). Choose only the largest and healthiest-looking ones for transplanting. When you look at the rhizomes you'll often find that the center is dead but both the ends have foliage attached. You can break the rhizomes to remove the dead centers and then replant the healthy ends. Place your divisions into the prepared soil. Make the holes deep and wide enough to take the roots without crowding. Set the rhizomes so they are just below the surface of the soil. This should do the trick. Remember to dead-head them (remove the flowers after they fade). Enjoy your garden!

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