Everything You Need to Know About Dividing and Transplanting Irises

Irises, named after the rainbow goddess of Greek mythology, are stunning perennials that come in a variety of vibrant colors and emit a delightful floral fragrance. These tall, elegant plants form beautiful clumps over time, thanks to their creeping rhizomes. However, when left unchecked, these clumps can become overcrowded, eventually leading to a decline in flower production.

To keep your iris stands strong and vibrant, it’s essential to divide and transplant them every three to four years. This process not only rejuvenates existing clumps but also provides you with new rhizomes to transplant to other areas in your garden. So, grab your gardening tools and let’s dive into the world of dividing and transplanting irises.

When to Divide

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To prevent overcrowding and ensure continued flower production, aim to divide your irises every three to four years. The best time to divide and transplant them is after they have finished flowering and become dormant in the summer. Wait about six to eight weeks after flowering or plan to do it from midsummer to early fall. Prior to dividing, make sure that the top layer of soil is dry, as it will make the removal process much easier, as the rhizomes and roots are close to the surface.

How to Divide and Transplant Irises

What You’ll Learn:

When to Divide
Lift the Clumps
Trim, Clean, and Inspect
Trim the Fans
Divide the Rhizomes
Replant
Choose Containers Wisely

Lift the Clumps

To start the division process, use a garden fork or spade to loosen and lift the clumps of irises. Insert the fork into the soil along the dripline, or about three to four inches outside of the visible rhizomes. Loosen the soil all the way around the clump before attempting to lift it. If the clump is too large to lift in one piece, use a clean, sharp spade or garden knife to divide it into smaller, more manageable sections.

Trim, Clean, and Inspect

After lifting the clumps, it’s essential to clean and inspect the rhizomes and roots. Use a soft bristle brush to remove excess dirt, making it easier to identify where to divide them. Trim and discard any pieces that do not have an attached leaf fan, as well as any dry, powdery, or smelly rhizomes. Inspect the remaining rhizomes for signs of pests or disease, discarding any that show symptoms of infestation.

Trim the Fans

Before replanting, trim the leaf fans of the irises to a height of six to ten inches. This will help the plants focus their energy on establishing healthy roots rather than supporting excessive foliage. Additionally, trimming the fans reduces the risk of wind damage, preventing the rhizomes from shifting before their roots have established.

Divide the Rhizomes

When dividing the rhizomes, ensure that each section has an attached leaf fan to produce flowers. Use a clean garden knife or scissors to cut the rhizomes into pieces about three to four inches long, leaving the roots intact. To prevent bacterial infection, dust the cut ends with powdered fungicide.

Replant

Irises thrive in full sun with well-draining soil and a slightly acidic to neutral pH. Ensure that the soil is loose and well-amended before planting the divided rhizomes. Create planting holes slightly larger than the rhizomes, mix in compost or manure for added nutrients, and plant the rhizomes with the tops exposed to the sun. Water gently but deeply after planting to help the roots establish.

When replanting irises in containers, choose dwarf or miniature varieties and ensure the pots have proper drainage. Fill the containers with a humus-rich soil, plant the rhizomes with the tops exposed, and water regularly to maintain soil moisture. Provide winter protection for container-grown irises by moving them to a frost-free location or adding a layer of mulch to insulate the rhizomes.

Ensuring Vigorous Blooms

To ensure a continuous display of vibrant blooms, divide your iris clumps regularly and replant the surplus rhizomes in various locations. Share the extras with family, friends, or neighbors as a thoughtful gift or for a local plant exchange. By dividing and transplanting your irises, you’ll not only maintain their health and vigor but also expand their presence in your garden.

If you have any questions about dividing and transplanting irises, feel free to drop us a line in the comments below. For more information on growing irises in your garden, check out the following guides: