How to Grow Reblooming Iris Plants

They're not just for spring anymore. Reblooming irises light up your fall garden.

When summer's lush greenness gives way to the sunset hues of autumn, you'd expect the garden to overflow with asters and chrysanthemums. But bearded iris? How did this flouncy flower of spring transform itself into an autumn beauty? Obviously, these aren't ordinary irises. These are reblooming irises, and they're changing the look of fall gardens.

It would take a trained eye in spring to spot any differences between reblooming iris and the more common once-blooming varieties. Both types flaunt sweet-scented fleurs-de-lis over a fan of leaves. But while most irises sit out the summer, rebloomers multiply in a frenzy of growth. By late summer or fall, they're ready to flower again. Where the growing season is long enough, reblooming irises are known to squeeze in a third or even a fourth flush of flowers.

Reblooming Types

Although commonly called rebloomers, there are several types within this category, according to the Reblooming Iris Society:

  • "Rebloomers" (also called "remontants") are irises that produce two or more flushes of bloom each year.
  • "Cycle rebloomers" produce a spring crop of flowers, lie low during summer, and grow and flower again in the fall.
  • "Repeaters" produce new flowers soon after the first spring flush dies back, extending the bloom season to one to two months.
  • "All-season rebloomers" produce flowers irregularly throughout the season.

There are two "catches" to this classification system. First, most retailers will say that a variety they carry reblooms, not what type of rebloomer it is. The other catch is that there are no guarantees that any particular sort in any specific setting will behave in any certain way. That said, most of the irises labeled as rebloomers by reliable suppliers will give you far more "bang" for your flower buck.

Consider Your Zone

In general, the reliability of reblooming iris declines as you go farther north. Gardeners in Zones 3 and 4 may see little or no reblooming. (The exception is the variety 'Immortality', which is reputed to rebloom as far north as Zone 3.) In most types, the reblooming cycle is set off by cooler weather, so if your temperatures are tropical year-round, you may not see a second bloom. Also, some varieties will not start reblooming for a couple of years, so patience is a virtue.

Planting and Maintenance

Because they're doing more work throughout the growing season, reblooming iris need more attention than regular varieties. Use a low-nitrogen fertilizer (one with a small first number, such as 5-10-20), following package directions. To prevent burning, don't allow the fertilizer to remain on the exposed rhizomes.

Feed the plants lightly in spring as growth starts, and again in September. Water every other week to keep the soil moist and prevent the plants from going dormant. This much water can cause regular irises to rot, so it's best to keep your rebloomers apart from your standard irises.

Reblooming irises grow faster than regular irises, so you'll need to divide them more often. To prevent overcrowding, divide reblooming iris every two to three years, but take only the outside rhizomes of the plant; leave the healthy older portions of the plant intact. Replant the small rhizomes 12 to 18 inches apart.

Like other irises, rebloomers can fall prey to iris borers and various diseases. If you spot signs of decline, talk to your county extension service about steps you need to take.

Reliable Rebloomers

Most rebloomers are bearded iris, though some Siberian, Japanese, and other species offer this trait.

Below are some of the most reliable reblooming bearded iris. Note: the time of bloom refers to the first flowering.

  • 'Autumn Bugler,' early, tall (28 inches), purple
  • 'Autumn Tryst,' early to midseason, tall (34 inches), violet and white
  • 'Baby Blessed,' very early, dwarf (10 inches), light yellow
  • 'Bountiful Harvest,' early, tall (33 inches), violet and white
  • 'Clarence,' midseason, tall (35 inches), white and violet
  • 'Corn Harvest,' early to midseason, tall (30 inches), yellow
  • 'Harvest of Memories,' midseason, tall (40 inches), yellow
  • 'Immortality,' midseason, tall (30 inches), white 'Jennifer
  • Rebecca,' midseason, tall (34 inches), rose pink
  • 'Sugar Blues,' mid to late, tall (36 inches), blue
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