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Repeat-Blooming Beard Iris

By William Scheick
Contributing Editor

They are “belles of the day” enjoying a “short reign of beauty.” So wrote Thomas Jefferson about bearded irises, one of his favorite flowers. A bearded iris bloom is indeed strikingly elegant: three upright petals (standards) with three arched petals (falls) ornamented by a fuzzy nectar guide.

Clearly, Jefferson lamented the transience of this perennial’s eye-catching splendor — the fact that bearded irises bloom once and briefly in early spring. How delighted he would have been to hear of a different scenario — repeat-blooming irises. Today, in fact, getting one-time bloomers to rebloom has emerged as an horticultural frontier, which now includes even new varieties of hydrangeas and lilacs.

Several years ago Renée Shearer gave me a crash-course introduction to reblooming (remontant) bearded irises. She had lived in Austin for 25 years before starting an iris business in Decatur in 2002. Eventually she moved to Waco and then, in 2005, hauled her many irises to Odessa, where she founded Wild Prairie Farm (www.wildprairie.com).

Unfortunately, Renée has recently told me, the iris farm will likely close. “For years I have promoted my farm heavily, given educational presentations year-round and physically managed everything alone while evolving as a pottery artist. When I had the opportunity to follow my true passion, I sold off my remaining remontant stock to different growers, kept enough in the ground to restart the business if I desired and to fill any unsolicited orders that come in.”

Renée has been featuring iris selections developed by Texan hybridizers, including Tom Burseen in Grand Prairie and Vincent Christopherson at Accent Iris Garden in Arlington (http://toolsbydesign.com/vciris). She proudly spoke of her remontants as “Texas-tough beauties born and bred in harsh growing conditions.” Irises capable of thriving in the “worst soil conditions of West Texas,” she believed, could grow just about anywhere.

Whether or not she closes her farm, Renée’s repeat-iris lessons are as enduring as passalong plants exchanged among friends over many years. And I’m passing on those lessons here.

REMONTANT BASICS
The bearded irises most commonly found in our gardens tend to blossom for only about two weeks in early spring. Some appear a little earlier, others a little later, depending on available moisture and sunlight. After blooming, their leaf-fans sit, often in prime garden spaces, for the next 50 weeks before they earn their keep by flowering the following spring.

Remontant irises bloom in the spring and then sometimes also in the fall. How often they flower varies based on their treatment and local conditions. Rebloomers inspire hope in a second show but come with no guarantee. “Each has its own character and will rebloom when it wants to,” Renée told me.

Basically, remontant irises require the same amount of care as do the more common tall bearded irises: excellent drainage in neutral to slightly alkaline soil exposed daily to at least five hours of sunlight. Excessive heat and dryness can impede iris flowering generally, but such conditions especially inhibit a rebloomer’s replay. Remontants must not go dormant due to protracted dryness, Renée advised, adding that drip irrigation is ideal for them. Repeat-blooming irises tend to need more water than more typical bearded selections and also extra feedings with a low-nitrogen, high phosphorus fertilizer, such as 5-10-5. Renée recommended feeding them on Valentine’s Day, Memorial Day, Labor Day and Halloween.

There is a good reason why rebloomers need more water and nourishment. All bearded irises sprout leaf-fans from thick underground stems (rhizomes). Usually it takes an entire year for an iris rhizome to produce a new bud and a flower stalk. Instead of one year, though, remontant irises complete this new growth cycle in one season. That’s their distinctive difference, Renée pointed out.

Individual varieties of bearded iris, including the remontants, commonly vary in their performance depending on their setting. In contrast to time-tested Texas iris passalongs, many of the elaborate and appealing iris hybrids marketed in plant nursery catalogs or sold in local box stores benefit from cold winters and mild summers. When planted in Texas, these rhizomes might flower for one or maybe two years, but then they often dwindle away. Generally, as advised by Joe and Donna Spears at their up-for-sale Argyle Acres Iris Gardens (www.argyleacres.com), “in Texas, bearded irises grow best north and west of US 59 (from Houston to Laredo). They require a definite winter season not found farther south or near the Gulf Coast.”

Being able to avoid guessing which irises will perform in our state was one reason why Renée’s “Texas-tough” iris hybrids have been such a boon. For those of us unable to grow our state’s moisture-loving wild irises — zigzag, giant blue and yellow flag — some iris-selection guidance can be useful. A wide variety of Texas-bred bearded irises, including miniatures, is available from Dana and Vernon Brown at Malevil Iris Gardens in Lubbock (http://www.malevil-iris.com). I have also found that various Texas-based iris societies are often extremely helpful when identifying which cultivars have performed well in their vicinities. Members of the Iris Society of Austin, for instance, pointed to ‘Cantina,’ ‘Fall Spotlight,’ ‘Eleanor Roosevelt,’ ‘Holy Kosmoly’ and especially ‘Daughter of Stars’ as reblooming-iris successes, though even these can be variable.

TROUBLE-SHOOTING
So far, my rebloomers have flowered beautifully each year, but they have never repeated. I blame myself. I’m neglectful, a “halfway-iris keeper” whose yard too often displays plenty of evergreen bearded iris leaf-fans but precious few flowers. I have even convinced myself that I just love those iris fans. After all, they are so durable despite the local weather and my neglect.

I know I should divide and replant my crowded rhizomes. And sometimes I do. But a year-round punishing lack of rain in my Central Texas area often puts unwelcome finishing touches on my best efforts. Relying on tap water that hasn’t been stored for a day, before use, unfortunately contributes chemicals detrimental to plant performance. In my case, too, tap water reinforces the alkalinity of my soil.

Which brings me to a phenomenon reported by some iris-keepers — a peculiarity concerning iris hue that I have seen for myself.

A good example of this phenomenon is described on the Letters page of the September-October 2010 issue of Texas Gardener. “I have had a strange thing this year,” Betty Johnson wrote concerning her formerly peachy-pink ‘Happy Birthday’ irises. “As the years have gone by … the color has lightened until they have been a sand color for a few years, until this year when the top level bed bloomed a perfectly snow white.”

A common explanation for this phenomenon is that white iris is an extremely aggressive rhizome that can invade and take over a bed. I have searched for and so far failed to find botanic confirmation of this widely held view of rampant white irises. The notion might be true; I just can’t confirm it scientifically.

I have found something else, though, that might pertain to the phenomenon. A clue, I think, lies in Betty Johnson’s suggestion of a hue-fading or bleaching sequence over time: peachy-pink becoming sand-hued in turn becoming whitish. She reports “a perfectly snow white” stage, but I wonder if, considered up-close, those flowers aren’t actually a pale off-white.

It is genetically impossible for irises to change color, but their capacity to express their color can be compromised. The successful floral expression of color requires certain levels of acidity in the petal cells. “Even mild shifts in acidity may alter their absorbance and color properties,” Dr. David Lee has explained in Nature’s Palette.

Besides acidity level, various chemical compounds (co-enzymes) in petal cell sap play an even a bigger role in the expression of color. These co-enzymes, Fritz Köhlein observed in Iris, can be impeded by one or more mineral deficiencies, or by an excess of some mineral(s). So soil environment is important generally to successful iris flowering and specifically to the expression of iris floral color. It is good to keep in mind, for instance, that bearded irises (in contrast to Siberian and Japanese irises) prefer a slightly alkaline to neutral soil pH, but much of Texas is way more alkaline than “slightly.”

The hue-fading or bleaching sequence of Betty Johnson’s irises over time suggests not a change in their color but, instead, their increasing inability to express their color. Of course, I turned to Renée for some insight.

She had heard of “the bleaching issue” (her words), though only from some of her southern customers. She recommended refreshing the iris bed’s “soil nutrients, probably depleted due to the overcrowding.” She added: “Fluff up the bed with compost and organic matter and water once a week when there is no rain.”

Reluctant to let Renée return to her gorgeous pottery, I wheedled for just one more insider tip about remontant irises. And then she revealed a secret, a practice she admitted is controversial. Renée mulched her irises with layered newspaper and bark — in Decatur she used hay — to within four to six inches of each rhizome. This newspaper mulch, she told me, retains moisture, controls weeds and decomposes/composts over time.

If Renée does close her farm, her Texas-tough irises will be missed. Her iris expertise, though, remains to be passed along.

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