Over the Rainbow with Iris

April 27, 2019

Named for the goddess of the rainbow, the iris genus contains more than 300 species. The color palette ranges from white to orange, pale blue to almost black. Only bright red is missing.


Native to Asia, Europe, Africa and North America, irises can be divided into three general groups, two of which grow from rhizomes and the other from bulbs. The rhizomatous ones are the familiar bearded iris and “flags” or beardless iris.


Let’s begin with the fragrant bearded iris, Iris germanica. The common name refers to tiny pale hairs on the lower flower petals called “falls.” The upper petals are referred to as “standards.” These are bulletproof perennials as long as you get off to a good start. They want full sun and excellent drainage. Plant the rhizome level with the surface of the soil. Flowering decreases when the clump becomes overcrowded, so they may need to be divided every three or four years to maximize flower production.


 Hybridizers have been working with bearded irises since the early 1800s when the western European native I. germanica  was crossed with Balkan I. pallida and I. variegata from eastern and central Europe. In the 1890s, a tetraploid species was introduced into England from the Middle East. Tetraploids have twice the usual number of chromosomes, which is associated with larger flowers. This species was used extensively in the United States, creating most of the bearded irises now available.


Reblooming iris have been available for several years. I have found the rebloom to be more aspiration than reality.


Flags are native to the marshes and wetlands of North America, Europe and Asia. In fact, it is a European species of flag that we see in the stylized fleur-de-lis of France. Sixth-century King Clovis found himself in a rough spot during a battle. He looked about and saw iris growing far out in the river, an indication that the water was shallow, so he and his men safely retreated and Clovis made the iris his emblem. Louis VII had it redesigned as we see it today.


Over one thousand years ago, the Japanese began working with two species. One with dark violet or white flowers is praised in a poem written in 760! The other, I. ensata, is the fabulous Japanese iris we grow today. They bloom in late spring bearing orchid-like flowers that are eight inches wide. These want evenly moist soil and tolerate boggy conditions.


Siberian iris also want rich moist soil. They have attractive narrow foliage and tolerate a range of situations. I once had a huge clump of dark-blue-blooming Caesar’s Brother growing in a French drain. I tried it in my bog garden but it sulked until overrun by Louisiana iris.


Louisiana is home to five marsh-dwelling iris species. There they happily mix and mingle resulting in naturally occurring hybrids. Needless to say, professionals have also worked to bring gardeners  these water-loving garden plants. These iris flourish in the bog. In fact they can be used in ponds as well.


The bulbous iris are from southern Europe and north Africa. In the early 20th century a hybrid of two of these species resulted in our Dutch iris. Miniature late-winter flowering iris are also in this group. They all want warm dry soil so that they can safely go dormant after flowering.


I have irises from all three groups in my garden. Blooming at different times, they add color interest over a long period from late winter through spring.


(Photos, from top: My personal favorite, Edith Wolford; late-winter-blooming miniature iris George; reblooming iris Touch of Spring; Miss Saigon; Louisiana irises growing in a marsh.) 


Master gardener Ann Bartlett never lets lack of familiarity with a plant keep her from trying it in the ornamental beds around her home. You can email Ann at arose56@hamilton.net.

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