QUESTION: When is the right time to divide irises?
Bearded irises, the large, showy flowers that have fuzzy patches on the outer petals, are putting on a pretty nice show across the region right now, and they’ll continue to bloom for several weeks.
After they have finished blooming, the rhizomes can be thinned out and divided if needed. But if you don’t get to it right away, you can wait until later. Irises are resilient and can survive being moved as long as they are re-planted properly.
Garden expert Judy Lowe recommends this method in her book, Month by Month Gardening in Tennessee & Kentucky:
Cut the leaves into a 6-inch high fan shape, then lift the clump with a spading fork and gently wash the dirt from the tubers. Cut off any soft, mushy or damaged parts, then cut the rhizome into smaller pieces, each with an eye or bud, using a sharp knife.
Lowe recommends dipping each rhizome into a fungicide solution to reduce the chance of fungal problems; one part liquid bleach to nine parts water is one suggestion to use.
Replant the rhizome sections close to the soil surface and water them well. Rhizomes of bearded irises should be planted so that their tops are visible above the soil. Iris beds should not be mulched.
In general, you may need to think iris beds every three to five years.
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“I wrote it for new gardeners and for those who like simple (easy) steps to follow that will help them succeed as gardeners,” she says.
The book features 101 container “recipes” that any novice gardener can follow – she tells what plants to buy, what size container to use, how to place the plants, and substitutions to consider if you can’t find (or don’t like) the suggested “ingredients.” But it’s also nice for experienced gardeners who are looking for new ideas. It’s published by Cool Springs Press; retails for $19.99 and you can order it through Parnassus Books and Amazon.