If you’re looking to move or multiply your irises, learning how to transplant iris bulbs is a key skill. It’s a simple process that revitalizes crowded plants and spreads their beauty to new spots in your garden.
Transplanting, often called dividing, is best done in late summer to early fall. This timing gives the rhizomes—the thick, bulb-like stems—a chance to settle in and root before winter. You’ll know it’s time when the center of the clump looks crowded or stops flowering well.
How To Transplant Iris Bulbs
This main guide walks you through the whole process, from digging up your irises to replanting them for success next season.
Gather Your Tools and Supplies
Having everything ready before you start makes the job smoother. You won’t need any speciality tools, just some basics.
- A garden fork or spade
- Sharp knife or garden shears (cleaned with a mild bleach solution)
- Gardening gloves
- Bucket of water
- Trash bag for old foliage and debris
Step 1: Prepare the Irises and the Site
Begin by cutting back the iris leaves to about one-third of their height, roughly 4 to 6 inches. This fan shape reduces wind rock and makes the plants easier to handle. Choose a new planting site that gets at least 6 to 8 hours of full sun and has well-draining soil.
Step 2: Dig Up the Rhizome Clump
Insert your garden fork into the soil about a foot away from the outer edge of the foliage. Gently loosen the soil in a circle around the clump. Work the fork under the mass and carefully lift the entire clump out of the ground. Shake off excess soil so you can see the rhizomes clearly.
Step 3: Divide the Rhizomes
This is the most important step. Look for the plump, healthy rhizomes with roots and a fan of leaves. Each viable division needs at least one fan. Discard the old, woody center sections that have no leaves. They won’t produce new blooms. Use your clean, sharp knife to cut the rhizomes apart, making clean cuts.
- Keep: Firm, light-colored rhizomes with roots and a leaf fan.
- Discard: Soft, mushy, or pest-damaged sections (like those with iris borer holes).
- Trim: Long roots to about 3 inches to encourage new growth.
Step 4: Inspect and Clean the Divisions
Take a moment to rinse the divisions in your bucket of water. This lets you inspect them closely for any rot or pests you might of missed. Let them air-dry in the shade for a few hours or up to a day. This helps the cut surfaces callus over, preventing rot when replanted.
Step 5: Replant the Iris Divisions
In your prepared sunny spot, dig a wide, shallow hole. Build a small mound of soil in the center. Place the rhizome on the mound, spreading the roots down the sides. The top of the rhizome should be just barely at or slightly above the soil surface. Burying it to deep is a common cause of failure. Fill the hole and firm the soil gently.
- Space divisions 12 to 24 inches apart, depending on the variety.
- Point the leaf fan in the direction you want the growth to go.
- Water the newly planted rhizome thoroghly to settle the soil.
Step 6: Post-Transplant Care
Continue to water your new transplants every few days for the first few weeks if rain is scarce. Avoid fertilizing at this time; you can add a low-nitrogen fertilizer in the spring. Mark the location so you don’t forget where they are over the winter.
Common Mistakes to Avoid
Even experienced gardeners can make a few errors during this process. Here’s what to watch out for.
- Planting Too Deep: Iris rhizomes need to bake in the sun. If covered with soil, they will likely rot.
- Overcrowding: Giving them ample space ensures good air circulation and reduces disease risk.
- Wrong Timing: Spring transplanting can interrupt the bloom cycle. Stick to late summer/fall for best results.
- Using Dull Tools: Crushing cuts from dull blades heal slower and invite infection into the plant.
When Will They Bloom?
Patience is key. Irises transplanted in the fall may put up a few blooms the following spring, but they often need a full season to establish. You can expect a really great display in the second spring after transplanting. This gives the plant plenty of time to develop a strong root system.
Caring for Established Iris Beds
To keep your irises healthy and minimize how often you need to divide them, follow a few simple care tips. A little maintenance goes a long way.
- Remove spent bloom stalks after flowering.
- Keep the rhizomes clear of mulch and leaf litter.
- Divide clumps every 3 to 5 years to maintain vigor.
- Watch for pests like iris borers in spring, removing affected leaves.
Frequently Asked Questions
Can you transplant irises in the spring?
You can, but it’s not ideal. Spring-transplanted irises often skip blooming that year due to the stress. If you must, do it very early, just as new growth emerges, and be extra careful with the roots.
How deep should you plant iris rhizomes?
This is the most critical detail. Plant them shallowly, with the top of the rhizome exposed to the sun. In very hot climates, you can cover them with a very thin layer of soil, no more than half an inch.
What is the best month to transplant irises?
In most regions, aim for July through September. This post-bloom period allows the plant to focus its energy on root development before the ground freezes. The exact timing can vary slightly by your local climate zone.
Why are my transplanted irises not flowering?
Several factors could be at play. The most common are insufficient sunlight (they need full sun), planting too deep, or the clump being to young and needing another year to mature. Over-fertilizing with nitrogen can also promote leaf growth over flowers.
Can you transplant irises after they bloom?
Yes, this is the perfect window. Wait until about 4 to 6 weeks after they have finished flowering. The plant’s energy has moved from the blooms back into the rhizome, making it a strong time for division.
Transplanting iris bulbs is a rewarding task that ensures the health and beauty of your garden for years to come. By following these clear steps and paying attention to timing and depth, you’ll be rewarded with vigorous plants and abundant, colorful blooms. Remember, a happy iris is a shallow-planted iris with room to breathe and plenty of sunshine.