I have a question about transplanting tall bearded iris. In most gardens, the iris are in full bloom now, except for the ones in my garden. I have them under a long needle pine tree, and for the last 4 – 5 years they have done great. This year, however, I only have 2 that are going to bloom. So, I have decided to divide and move them. When and how do I do this?
Wait until after your tall bearded irises have finished blooming to dig up any clumps that are in need of dividing and transplanting. The plants go semi-dormant after they flower, so you can move them without much problem.
If your schedule is flexible, it’s always easier on the plant if you can move it on an overcast day when a rain shower looks promising.
You will find the irises are easier to transplant if you first cut the leaves back to about 12-inches with a sharp blade or pruner. This makes the plant easier to handle and helps it recover faster if there happens to be root loss during the division.
The plants grow from rhizomes, which are just under the soil. Lift the rhizomes by working a spade under them. Then remove the clump from the soil. Next shake off the soil or wash the rhizomes with a garden hose. This will give you a better view of where to make the cut. With a clean, sharp knife, separate the clump, dividing the rhizomes with 2 or 3 fans of foliage attached.
Now you are ready to plant. Prepare a hole 8 to 10 inches deep and work in some compost. In the center of the hole create a mound of soil that rises almost to the top of the hole. Place the rhizome on top of the mound and spread out the roots. Refill the hole until it just covers the crown. After all the plants are in place, water them in.
Your newly transplanted divisions should bloom the following year.