How To Transplant Iris

If your iris patch is getting crowded or blooming less, it’s time to learn how to transplant iris. This simple task rejuvenates your plants and fills your garden with more color. The process is straightforward and one of the most satisfying jobs you can do. I’ll walk you through every step, from timing to aftercare.

Transplanting iris mainly involves dividing the thick, underground stems called rhizomes. These rhizomes multiply each year. When they get too packed, they compete for nutrients and space. This leads to fewer flowers. By dividing and moving them, you give each plant room to grow and thrive again.

When is the Best Time to Transplant Iris?

The ideal time is late summer through early fall. This timing is crucial for a few key reasons.

The plants have finished their blooming cycle for the year.
The weather is cooler, reducing transplant shock.
There’s still enough warm soil left for the rhizomes to establish new roots before winter.
It gives the plant a full season to settle in before next year’s bloom.

A good rule is to transplant about 6 to 8 weeks after the last blooms fade. In most regions, this means July, August, or September. You can transplant in spring if you must, but it may cost you that season’s flowers.

What You’ll Need

Gathering your tools first makes the job smoother. You likely have most of these already.

A garden fork or spade
Sharp knife or garden shears (clean them first!)
Gardening gloves
Hose or bucket of water
Trash bag for old foliage and debris
Optional: Bone meal or a low-nitrogen fertilizer

Choosing the Right New Location

Irises need plenty of sun and well-drained soil. Before you start digging up the old clump, pick your new spot.

Sunlight: Aim for at least 6 to 8 hours of direct sun daily. Less sun means fewer blooms.
Soil: They prefer neutral to slightly acidic soil. If your soil is heavy clay, amend it with compost or coarse sand to improve drainage. Wet feet cause rhizomes to rot.
Space: Plan for about 12 to 24 inches between each new division. They need air circulation.

Step-by-Step Transplanting Guide

Step 1: Prepare the Iris Clump

Start by trimming the leaves. Cut them back to about one-third of their height, forming a fan shape. This reduces water loss and makes the plants easier to handle. It also helps prevent wind from rocking the new planting.

Step 2: Dig Up the Rhizomes

Insert your garden fork or spade in a circle around the clump, staying a few inches away from the outer leaves. Gently loosen the soil and lift the entire mass out. Try to keep the rhizomes intact as much as possible. Shake off the excess soil.

Step 3: Divide the Rhizomes

This is the most important step. Wash the clump with your hose to see the rhizome structure clearly. You’ll see a network of thick, horizontal stems.

Look for plump, firm rhizomes with healthy roots and a fan of leaves.
Discard any old, woody centers that have no leaves or growth points.
Also toss any soft, mushy, or diseased sections.
Using your sharp knife, cut the rhizomes apart. Each division should have at least one fan of leaves and a set of healthy roots.
You can often break apart newer sections with your hands by giving them a firm snap.

Step 4: Inspect and Trim

Before replanting, give each division a final check. Trim the roots to about 3 inches long; this encourages new growth. Trim the leaves again to a neat 4- to 6-inch fan. This balanced trim helps the plant recover faster.

Step 5: Prepare the Planting Hole

In your new, sunny location, dig a wide, shallow hole. The hole should be just deep enough so the rhizome sits slightly below the soil surface. Mound a little soil in the center of the hole. This mound is where the rhizome will rest.

Step 6: Plant the Rhizome Correctly

Place the rhizome on the soil mound. Spread the roots down the sides of the mound. The top of the rhizome should be just barely visible above the soil line. This is critical. If you bury the rhizome to deep, it will likely rot. Backfill the hole, firming the soil gently around the roots. Water it in well to settle the soil and remove air pockets.

Step 7: Spacing and Aftercare

Space multiple divisions 12 to 24 inches apart. Water newly transplanted irises regularly for the first few weeks if rain is scarce. Do not overwater; the soil should dry slightly between waterings. You can sprinkle a little bone meal around the base, but avoid high-nitrogen fertilizers which promote rot.

Common Mistakes to Avoid

Even experienced gardeners can make a few errors when handling irises. Here’s what to watch for.

Planting Too Deep: This is the number one cause of failure. The rhizome must bask in the sun.
Overcrowding: Give them space. Crowded plants get diseases and stop blooming.
Wrong Timing: Transplanting in the heat of summer or too late in fall gives plants no time to establish.
Over-fertilizing: Too much fertilizer, especially nitrogen, leads to lush leaves and no flowers, or worse, rot.
Using Dull Tools: A clean, sharp cut heals faster and prevents crushing the rhizome tissues.

Caring for Irises After Transplanting

Your work isn’t quite done once they’re in the ground. A little care ensures success.

Keep the area weeded. Weeds compete for nutrients and water. In late fall, after a few hard frosts, you can cut the foliage back to the ground. Remove and discard this debris to keep pests and diseases away. In very cold climates, a light mulch after the ground freezes can help, but pull it away in early spring.

Come spring, you should see new growth. Be patient; a division might not bloom it’s first spring but should by the second. Once established, irises are quite drought-tolerant and low-maintenance.

FAQ Section

Can you transplant irises in the spring?

Yes, but it’s not ideal. Spring-transplanted irises often skip blooming that year as they focus energy on root growth. If you must, do it very early, as soon as the soil can be worked.

How often should irises be divided?

Every 3 to 5 years. You’ll know it’s time when the center of the clump looks dead and the flower production decreases.

Do you soak iris rhizomes before planting?

No, you should not soak them. After dividing, you can let them dry for a few hours to let the cuts callus, which helps prevent rot. Planting them in moist soil is sufficient.

Why are my transplanted irises not blooming?

The most common reasons are not enough sun, planting too deep, or using to much nitrogen fertilizer. It can also take a year for a division to recover and store enough energy to flower.

Can you transplant iris while they are blooming?

It’s strongly discouraged. Transplanting shocks the plant and will shorten the bloom time. It’s best to wait until the flowering period is completely over.

What do you do with iris rhizomes after digging them up?

Divide them immediately and replant the healthy sections. You can share extras with friends! Do not store them long-term like bulbs; they will dry out. If you must store for a few days, place them in a cool, dry spot.

Transplanting irises is a simple and rewarding garden task. By following these steps, you ensure your irises remain healthy and productive for years to come. The key takeaways are timing, keeping the rhizome exposed, and providing good drainage. With a little effort, you’ll be rewarded with a stunning display of blooms season after season.