The Intersection of Plants and People

How to Cross Bearded Irises

It’s fairly easy to cross Bearded iris, and the only tools needed are tweezers (or careful fingers), some large paper price-tags with strings, and a permanent marker. It’s also helpful to understand the basic anatomy of an iris.

From Matchmaking to Consummation

iris diagram 2

Bearded Iris Diagram

Bearded iris come equipped with everything they need to create the next generation:

1) The stamen, or male part of the plant, which produces the pollen, or seed. The stamen consists of a slender, wand-like filament that holds up the pollen-laden anther. In Bearded irises, the anthers are tucked under the “style arms,” described further below.

The pistil is the female part of the plant. In irises, this includes the ovary below the flower head. From that ovary, three “style arms” reach up into the bloom, looking to most people like just another part of the petals. Each style arm ends in a “stigmatic lip” or simply, the stigma. On a Bearded iris, the area where the style arms come up creates a space that resembles a gaping mouth, and the stigma does look somewhat like teeth just below the upper lip of the “style crest”.

A closer look into an iris reveals the "style arms," which resemble the Mitsubishi diamond logo. Part of the ovary below the bloom, style arms rise up to present both the stigma and the stamen within their cupped structure.

A closer look into an iris reveals the “style arms,” which resemble the Mitsubishi diamond logo. Part of the ovary below the bloom, style arms rise up to present both the stigma and the stamen within their cupped structure.

Because the anthers on Bearded iris are hidden under the stigma, it’s unusual for one of these plants to fertilize themselves. They need help from an insect, a strong wind, or more likely, a human being, for anything to happen that would result in seeds.

Ray Schreiner, the third-generation hybridizer at Schreiner’s Iris Gardens in Salem, Oregon, puts it simply when asked advice on how to begin breeding irises:

“Always use two good parents,” he suggests.

That means choosing disease-free parents with strong stalks, good branching, heavy substance (thickness of the petals), and good budding — enough buds for lengthy blooming, but not set so close to one another that they overlap awkwardly. When making a cross, blooms should be freshly opened — no more than a day-old is best, as both the stigma and pollen can get too dry for germination to occur.

Catherine Long, owner of Long’s Gardens in Boulder, Colorado, says that some hybridizers enjoy spending their winters poring over the registration books sold by the American Iris Society, which sometimes track the parentage of listed irises all the way back to the original species. These iris breeders are keen on genetics, and are seeking two parents that might yield specific traits in their offspring. Other hybridizers are more casual, using their observations of blooming plants to choose the qualities they hope to blend.

“People can have all these different approaches and get about the same results,” says Long, a third-generation iris grower.

Dust-like pollen clings to the anther of a Bearded iris.

Dust-like pollen clings to the anther of a Bearded iris.

The technical part of making the cross is not difficult at all. With tweezers or fingers, the stamen is plucked off close to the anther of the first plant (what will be the father). The anther is then rubbed onto what will be the mother iris’ stigmatic lip. The pollen is tiny but visible — a yellowish, white or bluish, grainy powder. It’s best to put pollen on all three of the stigmatic lips of the mother plant, just to get better odds of pollination. And, if more than one bloom is open on the mother plant, iris breeders often put the same pollen on those as well, increasing the chances of diversity among the sibling seedlings.

It’s important to “emasculate” the pollinated mother plant by pulling off its stamens, otherwise it could self-pollinate, resulting in seeds that are not the intended genetic mix.

Pollen clings to the sticky "stigmatic lip."

Pollen clings to the sticky “stigmatic lip.”

The next step is to write down the cross on a price tag, first listing the seed parent (the mother, which has been fertilized), then the pollen parent (the father, which provided the pollen):

Name of Mother Plant X Name of Father Plant

For example, you might have:

High Peak X Lady Friend

The tag should be attached to the sturdiest part of the stem, away from the blooms. Many times hybridizers will make a “reciprocal cross,” which means that, after they pollinate the mother plant, they take that plant’s pollen and put it on the father plant (so that it can experience the joys of motherhood as well).

To keep other hybridizers such as bees and ants away from a cross, many breeders pull off the petals of the mother plant. It’s a sad sight, but the bloom has done its job attracting a hybridizer. Once the glory of its beauty is removed, the plant is much less likely to attract other pollinators, leaving the ovary to get busy making seeds from the breeder’s cross. Taking off the petals is actually necessary in wetter climates, says Keith Keppel, a hybridizer in Salem, Oregon. In his rain-prone climate, intact petals can rot, causing decay that can destroy the developing seeds.

A Bearded iris in Robert Van Liere's garden is tagged with the coded name of a seedling cross. A pink ribbon alerts the hybridizer to not deadhead the aging bloom, which would destroy a newly developing seed pod.

A Bearded iris in Robert Van Liere’s garden is tagged with the coded name of a seedling cross. A pink ribbon alerts the hybridizer to not deadhead the aging bloom, which would destroy a newly developing seed pod.

After the initial matchmaking, it’s a matter of waiting to see whether the ovary on the mother plant swells — the sign that the cross has taken, and that seeds are being formed inside. If the cross didn’t work, the ovary will shrivel and drop off.

An ovary that’s developing seeds will swell to become a green, egg-shaped “pod” that ripens over the summer. Towards the end of the season, the pods will begin to turn brown and will dry enough to begin splitting open at the seams. This is the time to harvest — just before the pod cracks or just when the seeds are barely exposed enough to see. Once separated from the dry pod, the seeds can be placed in a paper envelope labelled the same way as the original tag to keep track of parentage.

Planting the Seeds

There are different ways to get Bearded iris seeds started. Depending on an iris breeder’s home climate and his or her patience, there are some ways to speed up how quickly an iris comes to bloom.

William Rickatson Dykes, after whom the highest award for iris hybridizers, the Dykes Medal, is named, explained in his 1911 book, Irises, that “raising Irises from seed is far easier and more certain than usually supposed.”

The method he describes is this:

“All that is necessary is to sow the seeds in pots early in the autumn and to plunge the pots outside in some cool position. Germination should ensue in the following spring, and in May, June and July, the young plants may be planted out in the positions where they are to flower. Given good soil, fair weather, and some attention in the matter of weeding and cultivation of the surface between the plants, the majority should flower in the following spring.”

A "pregnant" iris, its ovary swelled with developing seeds.

A “pregnant” iris, its ovary swelled with developing seeds.

This method is still used, but individual hybridizers have their ways of getting blooms sooner than two years’ time.

Robert Van Liere of Iris4u Iris Garden in Denver puts his seeds in envelopes when they ripen in Colorado’s sweltering August. In October, he plants the seeds in pots, then waters them up to six times a day for four weeks. This watering helps rinse off the natural chemicals on the seed coat which inhibit germination.

When the first hard freeze sets in, Van Liere puts the plants “to bed,” covering them with blankets to keep them cold for 90 days, so that the erratic Colorado winters, which alternate between sunny, 70-degree days and 30-degree dumps of snow, won’t turn on and off the process of “vernalization.” Vernalization is the technique of cooling a seed, bulb or seedling for a period of time to stimulate an earlier bloom after planting.

“I force mine to germinate in February so I can go from seed to flower in one year,” Van Liere says. “If I let them germinate on their own, they’re not going to be big enough to transplant until July or August.”

Going from seed to bloom in a year instead of in two years allows Van Liere to begin his selection process, culling the irises that don’t appeal to him, and keeping the ones he hopes will lead to a plant he’ll want to introduce for sale in the future.

Bearded Iris seed pods begin to crack open when the seeds are ready for harvest.

Bearded Iris pods begin to crack open when the seeds are ready for harvest.

According to Van Liere, other hybridizers have more unusual methods of getting their seeds to germinate quickly. One includes putting the seeds in a nylon stocking, which is then placed into a toilet tank. The soaking and flushing help rinse off the germination inhibitor. Afterwards, the breeder puts the seeds in wet paper towels with some vermiculite mixed in, then into the refrigerator for three months for vernalization.

In a southern climate like Texas, seeds collected in September can be planted right away, and will germinate fairly quickly. Since the mild winters may not produce a freeze until January or February, the seedlings can be transplanted by late fall or early winter of the same year that they were crossed. In cooler climates, seedlings started in a pot in the fall can be transplanted into the ground the following spring.

Evaluating the New Creations

While it’s thrilling to see the first bloom of an iris no one’s seen before, Long warns that “it’s very hard to judge things on their maiden bloom.”

New irises go through a kind of adolescence, and in the first year, it’s difficult for hybridizers to tell whether they have a plant that’s going through a temporary, awkward stage or that’s simply a complete dud. Other times, the bloom of youth is destined to wear off quickly.

“You can see it and think, ‘Wow, this is great!’ And then the next time it blooms the following year on a more mature plant, it’s like, ‘What was I thinking?’” Long says.

When a hybridizer decides an iris is worth saving, he or she will “increase stock,” keeping it in the ground to grow new side shoots from the base of the plant, the root-like rhizome. A rhizome is not a true root, but actually a horizontally growing stem. The rhizome on a Bearded iris resembles another rhizome used in cooking — the ginger root.

These two irises are genetically identical offshoots of the same mother plant. Still attached at the stem-like rhizome, they can be divided by cutting, and planted separately.

These two iris stalks are genetically identical offshoots of the same mother plant. Still attached at the stem-like rhizome, they can be divided by cutting, and planted separately.

Every year, the side shoots develop at the rhizome, creating new rhizomes and plant stalks. These can be divided by hand in mid-summer or fall, and each new fan-like group of leaves can be set out in the soil as its own plant. These side shoots are identical to the parent plant, and they themselves will grow a few new side shoots the following year.

Iris breeders may find that a young plant has a beautiful, unique bloom, but asymmetrical branching or a low bud count. The hybridizer will work with the plant, crossing it again and again with other irises, hoping that their desirable traits will help produce an iris with candelabra-like branching and enough buds to satisfy a gardener’s love of blooms. Over time, the breeder’s goal is that the iris becomes dependable enough in its growth to be formally introduced for sale. Some hybridizers, realizing that the iris is not ready for sale to the public, will offer the plant in trade with other breeders, so that the genetic material is available for tinkering.

Even an imperfect plant can be saved by hybridizers as a “breeder,” Long says.

“So it’s like some of us,” she laughs. “We could be a good parent, but have flaws.”


Once an iris is ready for introduction, the hybridizer registers the plant’s name and parentage with the American Iris Society, which records new iris varieties from around the world.

midamerica catalog

Mid-America Garden’s 2010 catalogue featured a kaleidoscope pattern of ‘Stir It Up,’ an iris bred by hybridizer Thomas Johnson. Online and print catalogs are produced by iris breeders every year to show off their latest introductions, as well as their more established stock.

A smaller farm like Long’s Gardens might want a hybridizer to provide 50 plants for the first year of introduction to sell to customers. A bigger grower might want 200 of the one variety.

Long, who works with hybridizers, helps them evaluate their plants and distribute them to a wider audience. Plants ready for introduction will be sent to national conventions two years ahead so that they can be well-established in time for the event, since divided and transplanted irises can take two years to bloom. Long also will give away an introduction as a bonus plant to customers with bigger orders, or trade it with other growers for their new introductions. The point is to get the new introduction into as many different gardens, soil conditions and climates as possible, where it will have to prove itself as a dependable grower and something that customers enjoy year after year.

As an accredited judge at regional and international iris shows, Long has the point-of-view of both a grower and a connoisseur.

“To really fully evaluate,” she says, “you should see something more than one season, hopefully see it in more than one garden to know — okay, this plant really seems to grow well, it’s vigorous, it seems to be disease-free, it sends up nice stalks, it blooms over a long period of time.”

To earn a Dykes Medal, an iris has to have won many other awards first. It can take decades to become eligible for the prestigious honor, but the result can be a plant worthy of becoming a treasured heirloom for future generations of gardeners.

One of Long’s favorite irises, ‘San Francisco,’ was the first Dykes Medal winner from 1927. It’s a variety that’s “tried-and-true,” the tagline her grandfather used for his seed business in the early 1900’s.

“In a year like this where we didn’t necessarily have a great year on Tall Bearded, it’s one of the things that dependably bloomed,” she says.

plantxing endnote (2)Photos by Benita Green Lee

4 comments on “How to Cross Bearded Irises

  1. A. Ripley
    May 4, 2014

    what is the name of that purple and red Iris pictured above/ I have been trying to find this Iris…to no avail. Help is much appreciated. have a great day!


    • Benita Green Lee
      May 14, 2014

      Absolutely stunning, isn’t it? It’s ‘Brash and Bold’ by Paul Black of Mid-America Garden. It’s actually an Arilbred Iris. Here’s a link to the online sales page:


      • Benita Green Lee
        May 15, 2014

        Sure thing! Arilbreds are very majestic and have a kind of exotic flair. You might enjoy some of the other cultivars out there as well.


        • Benita Green Lee
          May 17, 2014

          The irises will interbreed at least a little but your original plants will not change colors. If you saw a seed pod form on one in the summer, waited for it to ripen, then planted those seeds, you would get the offspring of those accidental crosses. The offspring would be different than the parent plants you have growing in the garden – though many of them might look very similar to one of the parents. Part of the fun of making crosses is the genetic grab-bag you end up growing – each seed is totally unique to the world.

          There are quite a few very dark irises out there. Try googling “black iris” or check out the iris growers listed in our Find section and search on their sites. The black irises can be very dramatic-looking in a garden!


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This entry was posted on September 10, 2013 by in Feature, Uncategorized and tagged , , , .
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