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How to Plant Bearded Iris

1 Jul 2021 1:00 AM | Brenda Peshak

Planting Bearded Iris

Iris rhizomes should be divided every 3-4 years.

Bearded iris (“German iris”) is among everyone’s favorite flower for late spring-early summer blossoms. If their growing conditions are met, they’re fairly easy to grow. However, like many garden treasures, they’re not completely maintenance-free.

Learn How to Plant Bearded Iris

  • Choose a sunny, well-drained site. Irises require 6-8 hours of sun daily. Sandy soil is good because iris cannot flourish in wet, clayey soil. If your soil is not well drained, consider amending with sand or planting in a raised bed. The idea is to keep the rhizome (the fleshy part with roots attached) relatively dry—otherwise it will rot.
  • Planting season is usually mid-July through August. Planting at this time allows time for settling in before winter.
  • Before planting, incorporate a low-nitrogen fertilizer into the soil. (Bulb fertilizer is a good choice.) Check the N-P-K numbers on the label. The first number needs to be lower than the second—e.g., 3-5-3 or similar. Always follow label directions. More is not In fact, “more” - too much may well burn new roots. Fertilize at planting time and the following early spring.
  • Water at planting time then only during very hot, dry periods. Too much moisture will rot bearded irises.
  • Space generously—18” between plants. Irises must have good air circulation to avoid disease, rot, and pests. (Anyway, they soon fill in!) If planting miniatures, 12” spacing is okay. The closer together you plant them, the sooner they will need to be divided. A crowded iris bed is an invitation to weeds, iris borers, and leaf spot.
  • Do not mulch. Although we’re told to mulch our plants, bearded iris is an exception. Too much moisture on the rhizome will certainly lead to rot. Of course, this means watching out for weeds!

How to lift and divide irises

  • Using a spade, shovel, or digging fork, lift the entire plant up and cut off all but about six inches of the leaves. (If you leave all the foliage, the roots will be stressed trying to maintain the leaves. Plus, the plant could topple during a rain storm, pulling the rhizome and roots out of the ground.)
  • Next, inspect the rhizome. Remove any damaged or decayed areas with a sharp knife or box cutter. If you’re dividing the plant, cut off the old woody section and discard it. It won’t bloom anyway. You can leave the healthy cut rhizome out in the sun to dry for a few hours or up to two weeks, but after that, it’s time to plant! If desired, dust cut ends with sulfur to discourage disease.
  • Since the roots may die anyway, especially if left out of the soil for a period of time, you can cut them back to about six inches. These will help anchor the plant in its new soil. Of course, if you re-plant immediately, no need to trim the roots, but you still need to trim the foliage back to avoid transplant shock.
  • When the divided rhizomes have formed a callous, you can plant them with the top quarter inch or so of the rhizome exposed to the sun. Do not completely bury the rhizome unless the soil is very sandy.
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