German irises can be propagated by dividing their rhizomes every few years. This process is called asexual propagation. 

When to divideĀ 

  • Divide in late summer, after the irises have finished flowering.
  • This allows the plants to become well-established and store carbohydrates.
  • Irises divided in late summer are more likely to flower the following spring.

How to divideĀ 

  1. Use a garden fork to dig up the iris clump.
  2. Shake off loose dirt.
  3. Pull the rhizomes apart by hand.
  4. Discard the old, woody center section.
  5. Select young, healthy rhizomes with at least one fan of leaves.
  6. Cut the rhizomes into pieces with a sharp knife.
  7. Trim the leaves by about half.
  8. Replant the rhizomes in fresh soil.

How to replantĀ 

  • Space the rhizomes 12ā€“24 inches apart.
  • Plant them in a shallow hole, with the leaves facing the sun.
  • Firm the soil around the roots, but leave the top of the rhizome exposed.
  • Water thoroughly.

Why divide

  • Dividing irises increases the number of blooms and reduces the risk of disease.Ā 

Over time, irises can become congested, which can inhibit flowering.