Acclaimed for their glamorous flowers gracing the garden in spring or early summer, some bearded iris varieties rebloom again in late summer or fall, offering us the pleasure of, once more, enjoying more of their colorful ruffles and mind-blowing flowers. As an added bonus, many reblooming irises bear sweetly fragrant flowers.

What are Reblooming Irises?

Reblooming irises are found in both beardless irises (Siberian Irises, Japanese Irises, Louisaina Irises or Aril Irises) and bearded irises (Miniature dwarf bearded, Standard dwarf bearded, Intermediate bearded, Miniature bearded, Border bearded, Tall bearded). 
There are different types of reblooming irises.

  • 'Rebloomers' (or 'Remontants"): they produce more than one crop of bloom stalks in a single growing season.
  • ​'Cycle Rebloomers': they complete two distinct cycles of growth, blossoming and increasing in any one growing season. The second new increase does not require any chilling period to produce bloom stalks and generally occurs in late summer and (or) fall.
  • 'Repeaters': they produce additional bloom stalks on old growth immediately following the initial production of spring bloom. These iris varieties frequently extend their spring bloom season from 4 to 8 weeks.
  • 'All Season Rebloomers': they can send up bloom stalks throughout the growing season. Their bloom time is not controlled by day length, but by soil temperatures.

Is Reblooming guaranteed?

  • Remontancy is not guaranteed and can depend on your geographic location, climate and cultural conditions. However, do not give up if you don't get your reblooming irises to rebloom the first year. Some varieties need to grow into a sizable clump and acclimate for a few years before they rebloom well.
  • Rebloom usually occurs between September and late fall (zone 5), in October (zone 6), in July (zone 7), in August or September (zone 8) and in September and later (zone 9). However, note that hot summer night time temperatures can trigger dormancy as does frigid winter temperatures.
  • Rebloom can also depend on your cultural conditions. While worth the extra effort, reblooming irises take a little more care than the once bloomers. They like a little more fertilizer and water since they need an extra boost to flower again (you don't want to let them go dormant). You should fertilize them in early spring and again after spring bloom. Use a fertilizer with a fairly low Nitrogen content, such as 5-10-5, mixed 50/50 with superphosphate (0-45-0). Water your irises at least once every other week if the rainfall hasn't been sufficient, so they don't dry out completely.

Tips:

  • You may want to grow your reblooming irises together or mark them in some way since the once bloomers may rot with the extra water and fertilizing.
  • Since most rebloomers increase faster than once bloomers, you may need to separate and replant them every second or third year. Since some cultivars need to be well established before they rebloom, you should divide and reset half of the clump and leave the rest to rebloom.