 |
||
|
Cornell University : Cornell Cooperative Extension
|
||
|
||
| Yates Association |
|
|
Irises - Growing, Dividing |
|
|
Garden irises are hardy, long lived perennials that need a minimum of care. They are an established backbone of home gardens as they bloom when few other plants do, after spring-flowering bulbs and before most other herbaceous flowers. Irises are categorized into three types, bearded, beardless and crested. All types grow from under ground stems called rhizomes. These rhizomes grow slightly below the surface of the ground or at ground level. Many small roots penetrate the soil deeply. Every year, underground offshoots develop from the original rhizome. These offshoots may be divided and transplanted to grow new irises. When selecting a site for new irises, keep in mind that they prefer full sunshine. Prepare the new bed one to two weeks before planting to allow the soil time to settle. Use commercial fertilizer to enrich poor soil in the bed, use organic matter such as compost to improve soil structure and productivity. In the well-prepared bed, dig a shallow hole large enough to receive the rhizome. Carefully spread the roots in the hole and fill with soil. Place the rhizome just below ground level. An iris planted too deep will not perform well. Firm the soil around the plants and water immediately, thoroughly soaking the soil around the roots. Plant rhizomes at least eighteen inches apart. In the fall, cut back the leaves six to eight inches from the ground and cover the rhizomes with a light layer of mulch after the ground freezes. Two to five years after planting, the rhizomes will become crowded and will need to be divided to assure continued bloom. Divide and transplant irises in the late summer or early fall. Trim leaves to one-third their full height. Dig under a clump of rhizomes and lift out the whole clump at once. Wash away soil with a steady stream of water. Cut rhizomes apart with a sharp knife. Each division must have at least one growing point, a few inches of healthy rhizome and a number of well-developed roots. Each division is ready to plant and will bloom the first or second year after planting. Cornell
Cooperative Extension Yates Association |
