What is the Right Time to Plant Irises
Most bearded irises are easy to grow, but they do have specialized needs. Plant and divide every 3 to 4 years in summer or early fall, splitting them into individual “fans” with the rhizome attached, or into divisions with a few fans. Trim leaves back before planting to make up for root loss. They grow best in full sun or very light shade and average to rich, well-drained soil. Barely cover the rhizome and point the leafy end in the direction you want it to grow, ideally out from the center of a group of three to five of a kind.
In fall, remove dead, dry leaves, which often carry borer eggs, and destroy badly infested fans in spring. You can also crush borers in the leaves by pinching toward the base of the telltale ragged-edged leaves or by running your thumb between the leaves and squashing any borers you find. They are also vulnerable when you divide the clumps; check every rhizome for this pest. If you find a few borers, try cutting them out, but destroy badly infested rhizomes.
Landscape uses: Smaller bearded irises are perfect in rock gardens and along paths and beds. For mid- to late-spring bloom, plant taller ones in a perennial border, or in a separate bed to provide optimum conditions. They also look splendid among garden ornaments and along patios.