Iris: Divide and Conquer

Grab the digging fork and head out to the garden; it’s time to divide iris. Here’s the quick how, when, and why.

How do you divide iris? Use a digging fork to lift the rhizomes from moist soil. Iris clumps can be ‘tough as nails,’ don’t be afraid to break apart the rhizomes (fleshy tubers) with the fork or a sharp knife. Wash off the rhizomes and look for any signs of rot; the rhizomes can appear soft, mushy. If found, you have two options – you can cut away all infected areas or, if severe, you can throw out. Your new division should include a fan of leaves, healthy rhizome, and roots.

A few helpful hints for replanting: It’s all about the soil, so spend a little time turning over and preparing the soil before you reset the fans. Heavy soils should be amended with compost or leaf mold. Before you replant, remove the top half of the leaves, also called fans. Set 3 divisions in a circle with the fans facing outward. With your hands, firm the soil around the rhizome, but do not completely bury, you want the top of it exposed. Water in after planting.

When do you divide iris? Late July into August is best; it allows the plants to set roots before winter arrives. Some gardeners will divide and reset iris every 3-5 years. You are the best judge for your own iris patch.

Why do you divide iris? Like everything else, Iris can grow tired and overcrowd its space. Dividing iris renews their vigor and flowering.