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Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

Home  >  Perennials and Grasses  >  Selection, Culture and Care  >  How do I divide my iris plants?

How do I divide my iris plants?

Bearded iris grow from thickened underground stems called rhizomes. Roots grow from these stems in the spring and again in the fall, during moist, cooler weather. They should be divided every three to five years to reduce crowding, and maintain vigorous clumps. Late summer is the time to divide iris, before the new roots are produced. Finish the job before October, so the plants have time to anchor themselves before winter. Iris require full sun and well drained soil.

To divide iris, dig up the rhizomes and wash away any soil. Examine them for rotting and holes in the rhizomes and leaves caused by iris borers. Cut these damaged areas out, and discard. Then, cut the healthy rhizomes into sections. Each section must have a fan of leaves and several inches of rhizome and healthy roots. Trim the leaves to one third their height. Dig a shallow hole in a sunny, well drained site. Make a cone of soil in the center of the hole and place the rhizome on it with the roots spread out. Cover with soil and water well. Iris are shallow growing. The rhizomes should be planted level with the soil. Space the divisions 18 inches apart.