Last September I divided an old clump of Siberian iris and moved the new clumps into a sunnier spot in the garden. This year, neither the old or the new clumps flowered although the leaves look beautiful! What should I do? Thank you, Jane
Thank you Jane for contacting Toronto Master Gardeners about your Siberian irises. I’m sorry to hear that you didn’t have any blooms this year. There are a number of reasons why Siberian irises (Iris sibirica) don’t bloom.
- Good light exposure is important. I’m glad you moved your Siberian irises to a sunnier location as they produce fewer flowers in too much shade.
- The timing of when you transplanted your irises may have resulted in lack of blooms this year. In colder climates, it’s recommended to divide and transplant Siberian irises right after they bloom, when new root growth is still active. Your plants may not have had adequate time to become established before the cold weather arrived. Note that the roots need to be kept moist while the plants are out of the ground and they need to be watered frequently after transplanting.
- The rhizomes should be planted 1” deep. Planting them too deep may result in no blooms.
- Iris sibirica also require consistent moisture from when the leaves emerge in spring until a few weeks after the flowers fade. We did experience some very hot, dry weather this spring so this could also have been a factor.
- Your soil could be a concern. Irises require well-draining fertile soil. An amendment of bone meal in early spring can help in the development of blooms.
- Overcrowding can negatively impact blooming but this isn’t a factor given the recent division of your plants.
- Last, a late freeze could kill any new buds that are forming. Toronto did experience freezing temperatures (and snow!) in late May.
As the leaves of your plants look very healthy, I wouldn’t give up on them. Enjoy their lovely grass-like foliage this summer. Hopefully next year you’ll be enjoying plenty of Siberian iris blooms in your garden.
June 30, 2021