Our grandparents grew bearded iris—or at least they tried. Most had tissue-paper flowers in pale gold or washed-out lilac that dissolved to mush in the rain. Their spindly stalks flopped during gusty spring storms, leaving the flowers spattered in mud and unable to open properly. Such disappointments should no longer trouble contemporary gardeners.
How to Select the Right Bearded Iris
Specialist iris growers have developed a fantastic array of varieties with clear colors, weather-resistant petals and sturdy stems. The advent of Internet buying makes it easier than ever to source new varieties of iris for your garden. However, the sheer number of bearded iris cultivars and the dazzling creativity of their names make choosing any one (or six) an intimidating prospect for novice fanciers.
Kelly Norris faced that choice as a kid gardener in rural Iowa and decided he had to have them all. Today, he runs a specialist iris nursery (Rainbow Iris Farms), wrote a book on bearded iris (A Guide to Bearded Iris) and serves as a judge and enthusiastic representative for the American Iris Society. “The AIS has almost one thousand new registrations a year, with six to seven hundred of those varieties being bearded iris,” Norris says. No wonder gardeners get bewildered.
Navigating the Choices
With so many options, how is a gardener to choose? Foremost, don’t get carried away by the beautiful flowers. Tom Johnson of Mid-America Garden in Salem, Ore., is an award-winning hybridizer of bearded iris. “If you just buy (an iris) for a flower that looks pretty,” he says, “you might as well have bought a picture and hung it on a wall rather than buying a plant.” His varieties have beautiful, clear colors and elegant forms, but they are also chosen to grow vigorously and reliably. “Most people are drawn to flower color,” he says, “but they should pay attention to the growth of the plant.”
Two aspects of a bearded iris cultivar’s growth are its vigor and its habit. How do you know if a bearded iris cultivar has good vigor? “At a minimum, each flowering rhizome should produce two offsets per season,” Johnson says. “A good grower will produce three or more.” The plant’s habit, or physical shape, is also important. Kelly Norris counts flower buds per stalk. The more buds, the longer flowering can last. “The standard is at least seven buds per stalk,” he says. Some cultivars can carry as many as eleven or twelve buds per stalk, which open in succession. “With several stalks on a two- to three-year-old clump, you can have up to three weeks of bloom,” Norris explains.
Strong stems are important as well. Anyone who’s grown heirloom bearded iris knows the sadness of walking out after a spring rain and seeing the stems tumbled to the ground, with sodden buds that will never open properly. “There is no excuse for a contemporary tall bearded iris to flop”, Norris says. He cites ‘Ten Carat Diamonds’, a new cultivar from hybridizer Gary Stagle, as an example. “Those stems are so thick,” he says, “I had to shave the stalks off with a vegetable peeler in order to get them to fit in the display bottle.”
Choosing a successful bearded iris cultivar also involves understanding the impact of geography on plant performance. To discover what varieties will grow best in your area, Norris suggests contacting your local chapter of the American Iris Society. They will be able to connect you with regional enthusiasts and offer advice on varieties with good local performance. Many societies also hold sales of plants grown in members’ gardens. If they have enough to sell divisions, then it’s likely a decent grower in your area. In addition, many botanic gardens have dedicated iris trial gardens. Visit during bloom season to find your new favorites.
Few of us are content with fields of iris alone. Instead, we combine our bearded iris with other garden plants. Too often, the iris plants get rangy and offer scarcer bloom—or, worse, they disappear altogether. For bearded iris to thrive in mixed borders, carefully choose companions with similar cultural requirements. “People mistake bearded iris for an English cottage garden plant,” says Tom Johnson. “They’re happier with cactus and succulents. They don’t play well with plants that require too much water.”
Gardeners in the Pacific Northwest have the luxury of using bearded iris amidst their agaves, echeverias and echiums as well as cottage-garden classics such as lupines and delphiniums. Gardeners throughout the continental climates of the United States have to look to a tougher range of companions. Prairie plants, with their low water needs and love of sunshine, make excellent companions for bearded iris in mixed plantings. “For a prairie version of lupines,” Norris says, “pair baptisia with tall bearded iris.” Recent breeding has widened the range of baptisias to include a slew of cultivars with clear or murky colors, mostly in blues and purples— but also whites, yellows and orange.
“Alliums and iris are another classic combination and easily repeated in different variations,” Norris says, noting that most alliums bloom in concert with early-blooming tall beardeds. He points to penstemons as potential matches for later-blooming varieties. Recent selections of Penstemon digitalis, such as ‘Pocahontas’ and ‘Dark Towers’, have purple foliage and pink flowers. Older seed-grown strains have variable foliage and looser clusters of white blooms.
In addition to companions with equally large and showy flowers, don’t forget plants with foliage that complements the bold clumps of strappy iris leaves. Prairie grasses, such as switchgrass (Panicum virgatum) and little bluestem (Schizachyrium scoparium), have graceful foliage that will contrast with the stiffly upright leaves of the bearded iris while subtly changing color throughout the year. Their fine leaves, glowing with light, sit as a soft backdrop to the grand blossoms of your glorious iris.
Step away from the dried-out rhizomes languishing in bags at the nearest box store. Make friends with your local iris fanatics, scout out a local show and peer through some specialty lists to find new bearded iris cultivars that will herald the summer’s arrival with flowers to make any rainbow look pale.
Caleb Melchior is a regular contributor to Horticulture. Visit his website for info about his latest projects.