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Irises are beautiful flowering plants that come in many varieties and colors. They are easy to grow and care for, but they do need some pruning to keep them healthy and blooming well. Pruning irises involves removing the dead flower stalks, cutting back the foliage, and dividing the rhizomes or bulbs every few years. Here is how and when to prune irises for better blooms.
Remove Dead Flower Stalks
Irises typically bloom in spring or early summer, depending on the type and climate. Some varieties, such as bearded irises, may also have a second bloom in fall. After the flowers fade and shrivel, you should remove the flower stalks to keep the plants tidy and prevent seed formation. Seeds can reduce the plant’s energy and vigor, and may not produce true-to-type plants.
To remove dead flower stalks, use a clean and sharp pair of pruners or scissors and cut the stalk at its base, close to the ground. Make an angled cut to allow water to drain off and prevent rotting. You can do this as soon as the flowers are spent, or wait until late summer or early fall.
Cut Back the Foliage
Irises have long, sword-shaped leaves that are attractive and provide structure and color in the garden. The leaves also help the plant produce food through photosynthesis, which is stored in the rhizomes or bulbs for next year’s growth and flowering. Therefore, you should not cut back the foliage right after flowering, but let it grow through summer.
However, in the fall, you should cut back the foliage to prevent diseases and pests from overwintering in the dead leaves. Irises are prone to fungal and bacterial infections such as leaf spots, blight, and soft rot. They are also vulnerable to iris borers, which are caterpillars that tunnel through the leaves and rhizomes.
To cut back the foliage, wait until the leaves turn yellow or brown, or until the first frost kills them. Then use a clean and sharp pair of pruners or scissors and cut the leaves back to about 3 inches above the ground. Dispose of the cut leaves in the trash or compost bin, but do not leave them on the ground.
Divide the Rhizomes or Bulbs
Irises grow from rhizomes or bulbs that multiply over time and form dense clumps. This can reduce the plant’s flowering performance and increase the risk of diseases and pests. To rejuvenate your irises and encourage more blooms, you should divide them every two to four years.
The best time to divide irises is after flowering, but before cutting back the foliage. This way, you can see where the flowers are and how crowded the plants are. You can also use the foliage as a handle to lift and separate the rhizomes or bulbs.
To divide irises, dig up a clump with a spade or fork, being careful not to damage the roots. Shake off any excess soil and inspect the rhizomes or bulbs for signs of rotting or boring. Discard any damaged or diseased ones and keep only healthy ones with firm flesh and green leaves.
Cut off any excess roots and trim the leaves back to about 6 inches long. Then break apart or cut the rhizomes or bulbs into smaller pieces, each with at least one fan of leaves and some roots. Replant them in a sunny location with well-drained soil, spacing them about 12 to 18 inches apart. Water them well and mulch them lightly with organic matter.
Summary
Pruning irises is an important part of their care that helps them stay healthy and bloom well. You should remove dead flower stalks after flowering, cut back the foliage in fall, and divide the rhizomes or bulbs every few years. By following these simple steps, you can enjoy your irises for many years to come.
