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Growing Tips: Reblooming irises add pizzazz to fall gardens

PHOTO BY DEBRA BURROWS A reblooming iris makes an elegant addition to this Clinton County garden in October.

Chrysanthemums and asters are often the workhorses of fall gardens here in Central Pennsylvania. As the flowers of summer blooming perennials fade, many gardeners look to mums and asters to keep things colorful during September and October. A lesser known, but equally beautiful fall-flowering addition to the garden is the reblooming bearded iris (Iris gemanica).

Although bearded irises are most commonly thought of as late-spring and early summer bloomers, reblooming varieties can produce a second wave of flowers in the fall here in Pennsylvania. Their tall, elegant bloom stalks create a nice contrast to the bushy habits of mums and asters. In addition to their visual appeal, some reblooming bearded irises are also fragrant.

Reblooming irises, which are sometimes referred to as “remontants” are varieties that have the ability to send up bloom stalks more than once in a growing season. It’s important to note that, while they have been bred to rebloom, repeat blooming is not always a given and some cultivars are more reliable repeaters than others. Adverse conditions, such as inadequate moisture or nutrients may prevent reblooming. Some varieties require several years of growth to become sufficiently established to rebloom. Climate is another factor. Most reblooming varieties do best in USDA Zone 5 or warmer locations, although a few cultivars have been shown to rebloom in colder zones.

In my Zone 6 garden, I’ve tried two reblooming tall bearded iris varieties, “Sugar Blues” and “Immortality” which have done very well. Both are considered reliable repeat bloomers.

The fragrance of “Sugar Blues” is sweet and delightful, so much so that I find myself spending extra time in that area of garden when it’s in bloom. It produces blue-purple flowers on strong stalks 30-36″ tall, rising above the foliage of other perennials and lasting for weeks in October.

“Immortality” is a slightly shorter variety which produces snow-white blooms. It is one of the few that will rebloom when located in Zone 4 gardens.

The variety and availability of reblooming irises has increased in recent years, providing gardeners with numerous choices as to color, height, fragrance, etc. To get an idea of the extent of cultivars available, I visited Schreiner’s Iris Gardens online catalog at https://www.schreinersgardens.com/reblooming-iris and was pleasantly surprised to see dozens of reblooming cultivars listed along with photographs and detailed descriptions. Color choices were extensive and there were many options for characteristics such as height, fragrance, smooth or ruffled falls (petals), stippling, etc.

Unlike many once-blooming bearded irises, which are usually tough, reliable perennials that require minimal care once established, reblooming varieties need a little more attention to encourage a second round of flowering. Providing the right conditions increases the likelihood of rebloom. Those conditions include a site that receives full sun (at least six hours of sun daily), supplemental watering during dry periods, and sufficient nutrients. Reblooming bearded iris tend to be vigorous growers and usually require more moisture and fertilizer than once-blooming varieties. They should not be interplanted with once-blooming irises because the additional water and fertilizer could actually be detrimental to the once-blooming varieties.

Detailed information on growing reblooming irises is available from the Reblooming Iris Society at https://www.rebloomingiris.com/Culture/.

Irises belong to a big family (Iridacea) and bearded irises are not the only members capable of reblooming. Certain cultivars of both Siberian (Iris sibirica) and Japanese irises (Iris ensata) are repeat bloomers as well. With so many choices now available, reblooming irises can add both color and fragrance to the fall garden, and in so doing, add a little bit of pizzazz to our autumn landscapes before the gray days of winter are upon us.

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Debra Burrows, PhD is a retired Penn State Extension Educator and certified Master Gardener. She can be reached at dcb3@psu.edu .

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