1. Q. I love to grow iris but my entire planting bed does not bloom as it once did. Should I replant? My neighbor has beautiful iris that I could replant with. When should iris be transplanted?
A. Iris beds need "thinning" periodically (every two or three years). September is the ideal time to plant or to divide and replant iris - the common man's orchid. Here's how it's done.
Before digging rhizomes (roots), cut leaves back to about one-third their full height. Dig under a clump of rhizomes, and lift out the whole clump at once. When dividing and replanting, use only the strong, healthy rhizomes for planting.
Cut rhizomes into sections, containing one to three buds. Each division must have at least one growing point (or fan of leaves), a few inches of healthy rhizome, and a number of well- developed roots.
Discard diseased and stunted plants. Disinfect pruning shears if you accidentally cut into a diseased rhizome using a solution of one part household bleach to nine parts water.
Plant iris in a sunny, well-drained area with good circulation around the plants to prevent diseases. If the soil is poorly drained, consider using raised beds, since iris will rot in poorly drained soils.
After planting, water the bed thoroughly to settle the soil around the roots. Usually no additional moisture is required unless a prolonged water drought occurs.
2. Q. When is the best time to transplant and/or separate iris? How should I prepare the planting site?
A. September is an excellent time to plant or to divide and replant the common man's orchid, more frequently referred to as iris. The new beds should be prepared at least a week prior to planting to allow the soil to settle.
Select a loamy soil in a sunny, well-drained area of the yard. If soil is poorly drained, consider using raised beds as iris will not tolerate wet, poorly-drained soil as the rhizomes tend to rot. Incorporate a complete fertilizer into the upper 6 to 10 inches of soil using one pound per 100 square feet of bed area. Also apply superphosphate at the rate of one-half pound per 100 square feet of area.
When dividing and replanting use only the strong, healthy rhizomes for planting. Cut rhizomes into sections containing one to three buds each. Discard diseased and stunted plants. To plant the prepared rhizomes, form a mound of soil in the bottom of the planting hole so that the top of the mound is about one inch below the surface of the bed. Place the rhizome on top of the mound with the roots spreading outward. Press the rhizome into the soil mound until it is at or below the soil level then finish filling the hold so the roots are covered and the rhizome is just barely covered.
There is a mistaken idea that iris foliage should be pruned back each year. Actually there are only two reasons to justify this practice. The first is to prepare the plants for digging and transplanting and secondly to remove diseased foliage especially at transplanting time. When trimming the foliage, cut it back to one-third its original height. In established beds, do not cut the foliage as it is needed to build up food reserves for flowering the next spring.
After planting, water the bed thoroughly to settle the soil around the roots. Usually no additional moisture is required unless a prolonged water drought occurs. Iris usually suffer more from too much water rather than a lack of moisture; however, they can be damaged if the roots and rhizome are allowed to become completely dry.
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