Dividing a Bearded Iris
Irises provide some of the earliest spring color in the garden, from white to purple too many other colors of the rainbow. Managed planting of individual irises, genetically programmed to bloom at different times of the year, can provide you with a succession of iris blooms over several months. The white irises usually start the parade.


The significant structural element of an iris plant is the rhizome. This modified root that grows at the surface of the soil is an anchor and food storage element. The rhizome needs to have some surface exposure to the sun. The leaf blades and bloom stalk grow upward out of the rhizome and feeder roots for water and mineral absorption grow down into the soil. The rhizome puts out buds along its sides that can be separated into new plants. This bud production can result in crowding making it wise to periodically dig up the rhizome, separate the buds, and replant the separated rhizome and buds. The feeder roots can be trimmed to 3-4 inches at transplanting, serving only as anchors for the newly replanted rhizome. Trim the leaf blades to 3-4 inches also to prevent dislocation of the replanted rhizome. It is very important that the underside of the transplanted rhizome maintain contact with the soil. Eventually a shriveled old mother rhizome can be discarded as it will have spent its energy and cease to leaf and bloom. Because this rhizome is able to survive out of the soil when dug up, it is one of the easiest plants to transplant.

After blooms are spent, the bloom stalk can be cut back. Leaving the blades will continue the process of food production for the plant which will be stored in the rhizome. After the bloom cycles are over, the leaf blades can be a significant background element in your beds. You may want to trim off any browning edges, but leaving the rest of the leaf blade will be a benefit for the plant.

Irises are colorful with long lasting foliage for your beds, are hardy and easy to transplant, factors that make them a wise addition to any landscape. The fact that flourishing untended irises can be found at abandoned homesteads and cemeteries testifies to the fact that the plants can be self-sustaining.
Be careful with the seeds because they are very small so you may want to work over a bowl. Put them in seed raising mix and keep them just barely moist. Put the pot in semi shade, so it doesn't dry out. If it is fresh seed they should start to germinate after six weeks, if it is old seed it is better to soak it for a few days, changing the water daily. If the seed is from bearded irises, put the seed in some damp peat moss or paper towel, roll up in a sandwich bag and put them in the vegetable crisper for a few weeks. You may even have some seed starting to germinate after this time. Plant them out into the garden or larger pots in early spring and you may get some blooms on them the following spring. Expect a wide variety of offspring if they are bearded or Louisiana iris. Even if they look exactly like the parent plant, they will be genetically different.

Dividing Iris
Iris should be thinned or divided before they become overcrowded, usually every 3-4 years. If your irises are too crowded, they may look good but they won’t bloom as well and disease problems may occur. Old clumps may be divided by removing the old divisions at the centers of the clumps and leaving new growth in the ground. Or one may dig up the entire clump, examine rhizome and look for bacterial and crown rot. Remove and destroy any infected plant parts to avoid the spread of these diseases to healthy plants nearby. It would be wise to soak iris in a diluted solution (1-9 ratios) of bleach and water for several hours or even overnight before replanting the large new healthy rhizomes. If planting in the fall when dormant, one may wish to cut back existing roots to about three inches. To plant a rhizome, dig large hole, fill the center with a mound of well-drained amended soil and set the rhizome on top of the mound with their roots fanned out around the iris. The iris should be planted so the tops of the rhizomes are exposed and the roots are spread out facing downward over a mound in the soil. The rhizome its self should sit at about ground level. Firm the soil around each rhizome and then water.

Tips: from Guenette Bledsoe:


A common mistake is over watering iris in the hot summer months of June, July, and August. Over watering causes bacteria and crown rot. Fans of iris will turn brownish yellow and will eventually fall to the ground if they’re receiving too much water. In the cooler part of fall, iris will bounce back. They will be making new rhizomes then, too. In late fall or winter when the weather is cool, iris can handle more water. Another common mistake is to plant iris too deeply. Healthy green leaves should be left undisturbed, but diseased or brown leaves should be removed and discarded.

After blooms are spent, the bloom stalk can be cut back. Leaving the blades will continue the process of food production for the plant which will be stored in the rhizome. After the bloom cycles are over, the leaf blades can be a significant background element in your beds. You may want to trim off any browning edges, but leaving the rest of the leaf blade will be a benefit for the plant.

Irises are colorful with long lasting foliage for your beds, are hardy and easy to transplant, factors that make them a wise addition to any landscape. The fact that flourishing untended Irises can be found at abandoned homesteads and cemeteries testifies to the fact that the plants can be self-sustaining.

Step by Step on Dividing Your Iris:
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1. Carefully dig the clumps with a garden fork or spade taking care not to chop into the rhizome.

 

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2. Divide the rhizomes by pulling them apart with your hands. In some cases, you may need to use a sharp knife to separate the baby rhizomes from their mothers. If so, dip your knife into a 10% bleach/water solution between cuts. A good rhizome will be about as thick as your thumb, have healthy roots and have one or two leaf fans. Large, old rhizomes that have no leaf fans can be tossed.

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3. Wash soil off the rhizomes so you can look for iris borer (a fat, white worm). If you find a borer, destroy it. Some gardeners like to wash their iris rhizomes in a 10% bleach solution to protect against disease but that won't help plants that are already rotting. Soft, smelly or rotting plants should be destroyed. Discard any plants that feel lightweight or hollow and appear dead.

 

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4. Clip off the leaf blades so that they're 4-6 inches long. This reduces stress that the plant goes through asset concentrates on re-growing new roots instead of trying to maintain long leaves.

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5. Replant divisions, setting the rhizome higher in the planting hole than the fine roots, which should be fanned out. A bit of the top surface of the rhizome should be just visible at the soil surface.

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6. Space the plants 12-18 inches apart (closer for dwarf varieties, farther apart for larger varieties). For great display, consider planting the rhizomes so the fan of leaves face the same direction. Water them at planting time but after established; only if the weather becomes dry.
What is the best time to divide iris for replanting or sharing?


Divide iris in late August and then water sparingly until the weather cools. When there is too much water and it is hot, irises are susceptible to rot. Once rhizomes are clean, look for small-medium holes. These are telltale signs of borer damage. If your bearded iris leaves have dark streaks in them, you probably have iris borers, so look closely. Also look for soft spots because this is another common iris problem called soft rot. Using a sharp knife, remove any traces of either iris borer damage or soft rot and dispose of these segments of rhizome. Soft rot spreads easily, so disinfect your cutting tool with denatured alcohol between cuts, to prevent further contamination. If you are in doubt whether the rhizome is good or not, just throw it away.

Hopefully, this has given you a good primer on dividing Iris's and you will plant your garden abundantly with these wonderful plants.