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September 13

Irises-Part II
Posted on September 13th, 2011 at 6:36 PM by Newark Ohio Garden Club

Dividing and Transplanting Irises-Part II

Preparation

If possible, till the soil a week or so before planting. Avoid adding barnyard manure because this can rot the rhizomes. If your soil is heavy clay, you may stir gypsum into the soil. Avoid adding peat moss because it is acidic. Irises prefer alkaline soil.

To improve any poorly drained area, you may want to build raised beds.

Dividing

It is best to do the digging, dividing and transplanting all in one day. This increases survival rate of your plants. Do one clump at a time.

Carefully lift each clump of iris out of the ground with a spading fork. If possible, lift the mass whole. You may need to break the clump apart to get it all out of the ground. Clean as much dirt off each iris as possible before dividing.  Dusting off dirt will make it easier to divide the clump. It is very important to inspect the rhizomes for soft spots and iris borers. (Iris borers are plump pinkish caterpillars that can kill your plant). Cut off any soft, insect -infested or unhealthy looking parts.  Discard any old, infested, mushy or bad smelling growths.

With pruning shears or a sharp knife, trim any broken or torn roots. With a sharp knife divide the remaining rhizomes into pieces. Trim the leaves to about 6-9  inches to reduce the need for moisture before replanting.  Each piece for replanting should have some healthy looking roots and at least one fan of leaves.

Transplanting

Select a location that is  sunny and well drained. Dig a hole for each clump.  You may add compost and stir into the soil. If desired, you may add bone meal to the soil but take care to mix the bone meal well into the soil. The iris roots can be burned if they touch the bone meal.

Position the rhizome so that it will settle into the ground just below ground level. Be careful not to plant the rhizomes too deeply or the plant will produce foliage but never bloom.

For a striking display, plant the iris rhizomes in groups of 4-6.  Space the rhizomes 12-16 inches apart.

Water thoroughly.

References

Planting and Dividing Bearded Irises by Don Janssen, Extension Educator, Lancaster County, University of Nebraska

Gardening Experiences: Dividing Bearded Irises by David Ross, 1999

prepared by Joan Cullen

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