Using Species in MDB Breeding, Part 3: Iris reichenbachii x Iris pumila

by Tom Waters

This is the conclusion of a three-part posting describing projects with miniature dwarf bearded (MDB) and standard dwarf bearded (SDB) irises. The first and second installments were posted in July and October 2023. 

My goal for this hybridizing project is to produce a true-breeding line of MDBs that belong to the same fertile family as the SDBs and MDBs from SDB breeding. In theory, using species and species hybrids that are compatible with SDBs will circumvent the tall bearded ancestry that can lead to larger, out-of-class plants. The earlier installments cover the use of Iris lutescens and of a hybrid of Iris aphylla x I. pumila. 

The current post describes work with seedlings from I. reichenbachii x I. pumila. This third avenue of work is, to me, the most exciting and promising. However, I got started with it a bit later than the first two approaches, so it is less far along.

I. reichenbachii is a species native to the Balkan peninsula. It comes in both diploid and tetraploid forms. (The tetraploid species I. balkana is considered a synonym of I. reichenbachii.) Plants typically have very slender stems topped with two buds, ranging in height from about 6 inches to about 12 inches. Flowers are either yellow in color or some blend of violet, brown, and gray. This species is probably best known as a parent of Paul Cook’s famous ‘Progenitor’ (R. 1951), which introduced the dominant bicolor pattern into tall bearded irises.

The tetraploid forms of the species belong to the same fertile family as TBs and I. aphylla. Hence crossing it with I. pumila ought to produce plants compatible with SDBs, just like the aphylla x pumila cross described in part 2.

tetraploid I. reichenbachii ex Mt. Vikos, Greece

I have raised a number of these (cross S026) from crossing a yellow tetraploid I. reichenbachii from Mt. Vikos, Greece, with I. pumila ‘Royal Wonder’ (Coleman, 2013). About half the seedlings are yellow and half are purple. They are all about 5 inches tall, with one or two dainty flowers per stalk. Because I. reichenbachii is so much smaller and daintier than I. aphylla, I believe these plants have even greater potential to produce consistently small and dainty MDBs. I have made as many crosses with them as possible. So far, they are not cooperating as pod parents, although they produce plenty of fertile pollen.

S026-02
I. reichenbachii X 'Royal Wonder'

 

S026-05
I. reichenbachii X 'Royal Wonder'

    

I am eagerly awaiting bloom in 2024 of seedlings from ‘Miniseries’ (Keppel, 2011) X S026-02. Still in the pipeline are crosses of the S026 seedlings with ‘Arson’ (Keppel, 2016, SDB), ‘Come and Get It’ (Black, 2013, SDB), ‘Dollop of Cream’ (Black, 2006), ‘Oh Grow Up’ (Miller, 2018), ‘Pearly Whites’ (Black, 2014), ‘Self Evident’ (Hager, 1997), ‘Tasty Treat’ (Johnson, 2020, SDB), and ‘Pirate’s Apprentice’ (Hager, 2003). 

Multi-generational breeding projects like this one require patience and a certain amount of faith in the theory behind them. It can be a long slog with little immediate gratification. But it can also be very satisfying to pursue curiosity about paths not taken before and to learn as one goes. For me, this type of undertaking matches well with my limited space and my penchant for careful planning. Perhaps in a few more years, the groundwork described in these three posts will yield something worthy of being grown in gardens or meriting the attention of other hybridizers. Until then, the learning itself is a fine reward.

Progress with Arilpums

by Tom Waters

When I wrote my previous blog post on arilpums early in 2019, I had to focus mostly on history and theory, as I did not yet have much to show from my own seedlings. That has now changed, and the current state of this project is even better than I had dared hope.

As explained in the previous post, arilpums are arilbreds dwarfs that come from crossing pure arils with the dwarf bearded species Iris pumila. If the aril parent is a tetraploid, theory says the resulting arilpums should be fertile amphidiploids, a sort of arilbred analog of the SDBs. They thus have the potential of ushering in a whole new "fertile family" of miniature arilbreds.

Waters Q025-01

This spring, I bloomed two arilpum seedlings, both prolific two-year-old clumps covered in bloom. The first, Q025-01, from 'Merlin's Magic' (a selection of Iris stolonifera) x P002-05, a pumila seedling of Armenian origin, has a dainty Regelia look and some nice veining. The second seedling, Q053-01, from 'Tadzhiki Bandit' x 'Sudden Butterflies' is larger and huskier, with flowers reminiscent of tall arilbreds with Regelia ancestry, such as 'Stars Over Chicago' or 'Saffron Charm'.

I also had good bloom this year on an arilpum seedling from

Waters Q053-01

George Hildenbrandt, GH-11-4-2, from 'Dunshanbe' x 'Hidden Dragon'. This is a charming dark arilpum with nice aril-like flower form.

Hildenbrandt GH-11-4-2

The remarkable thing is that all three of these seedling produced seed for me this year when crossed with other arilpums. In my previous post, I mentioned that earlier hybridizers working with arilpums had found them to be infertile as pod parents. That is clearly (and thankfully!) not a general rule! Here are my successful arilpum x arilpum crosses this year:

Q053-01 x Aladdin's Gem gave 38 seeds

Q025-01 x Q053-01 gave 9 seeds

GH-11-4-2 x Q053-01 gave 23 seeds

GH-11-4-2 x Aladdin's Gem gave 3 seeds

These are not huge seed yields, but they are certainly adequate for continued breeding. I am quite optimistic that a number of the second-generation seedlings from these crosses will be fully fertile, and it will be possible to line breed arilpums without having to constantly go back to the difficult aril x pumila initial cross. This will also open up arilpum breeding for hybridizers who live in areas where either arils or pumila are difficult to grow.

Next spring should offer even more excitement, as I have more than 30 arilpum seedlings from various crosses that will be blooming as two-year-old plants. I got a sneak preview of one this spring,  Q066-08, from 'Tadzhiki Bandit' x P018-02, a pumila seedling originating from the Caucasus mountains. It looks for all the world like a miniature rendition of its aril pod parent, giving a rather more "onco" impression than others mentioned in this post. It has not yet been tested for fertility.

Waters Q066-08

All this has been an exciting vindication of a breeding project motivated mostly by theoretic possibilities rather than concrete experience. I'm now confident that arilpums have a bright future ahead.

Hybridizing with Iris reichenbachii

by Tom Waters

Four years ago, I wrote a blog post here titled “The Untapped Potential of Iris reichenbachii”. At that time, I could comment on the use of I. reichenbachii in median breeding only as a promising theoretical possibility. Now, however, I have some solid results from my own hybridizing work to share.

As mentioned in the earlier post, I. reichenbachii exists in both diploid and tetraploid forms. The diploid forms can be used with diploid MTBs, while the tetraploid forms are compatible with TBs, BBs, and tetraploid MTBs. It was the tetraploid grouping that I was interested in, so my first priority was to acquire tetraploid forms of I. reichenbachii. Alas, none of the plants or seeds available commercially or through seed exchanges have been identified as either diploid or tetraploid, so I had to make this determination myself. Not being equipped to make chromosome counts, this meant making test crosses and patiently waiting for the results.

Happily, it turns out that the tetraploid forms are not uncommon. The first two reichenbachii forms I started crossing with both turned out to be tetraploid. One is a yellow form, a collection from Mt. Vikos in Greece. The second is actually a group of plants of unknown origin I raised from seed obtained from a collector in Czechia. Most of these are violet.

I. reichenbachii ex Mt. Vikos, Greece

Waters T009-02, purple tetraploid I. reichenbachii

Waters T051-01,
I. aphylla X I. reichenbachii ex Mt. Vikos

I have three fertile tetraploid seedlings now. The yellow Mt. Vikos form gave me seedlings with I. aphylla and with the tetraploid median plicata ‘Saucy’ (Craig, 1998, IB). One of the violet forms gave me a seedling with the tetraploid median ‘Night Mood’ (L. Markham, 2003, SPEC-X). All three of the seedlings fall in the SDB height range and have the slender stems of I. reichenbachii. None are any competition for the modern, ruffled, dramatically colored median hybrids being produced these days; rather, their value is in further breeding. Because these plants are so small and dainty, they can be used to add these qualities to tetraploid MTB or BB breeding programs. So the next step is to cross these seedlings with the best modern BBs and tetraploid MTBs. It would be nice to have all the color patterns, form, and substance the modern BBs have to offer, but in a line of plants that was consistently small and delicate. This project is already well underway, as I have hundreds of seeds from using these seedlings over the past two years.

Waters T059-02,
Saucy X I. reichenbachii ex Mt. Vikos

Waters T060-01,
Night Mood X T009-02

A second project using I. reichenbachii is directed toward producing dainty MDBs. Most modern MDBs are produced by accident - they are just seedlings from SDB crosses that fall below the 8-inch height limit. These MDBs can be very lovely in terms of flower form and color pattern, but they can easily grow out of class, and often lack the daintiness and early bloom that one hopes for in a true miniature dwarf.

SDBs are the result of crossing TBs with the dwarf species I. pumila. What if one used I. reichenbachii instead of TBs? The result should plants fully fertile with SDBs and modern MDBs, but much smaller. I have three seedlings so far (more on the way) from crossing the Mt. Vikos reichenbachii with the I. pumila cultivar ‘Royal Wonder’ (Coleman, 2013, MDB). One is purple, the other two are yellow. All our about 5 inches tall, with one or two terminal buds. They bloom earlier, overlapping the pumilas and the first MDBs. They are indeed fertile with SDBs and with MDBs from SDB breeding. Once again, the value of these seedlings is not in competing with the showiest modern hybrids, but in further breeding, where they can be expected to produce a line of consistently dainty and early-blooming MDBs. Again, this project is on its way forward, with many seeds from using these seedlings with modern MDBs and SDBs.

Waters S026-01,
I. reichenbachii ex Mt. Vikos X Royal Wonder

Waters S026-02,
I. reichenbachii ex Mt. Vikos X Royal Wonder

These projects using I. reichenbachii are not for the impatient; they are multi-generation endeavors. Yet, there is something uniquely satisfying in breaking new ground.

The Legacy of 'Anacrusis'

by Tom Waters

'Anacrusis' (Mathes, 1992), OGB/ABM

There is a very interesting line of irises created by Harald Mathes of Germany, beginning with 'Anacrusis' (Mathes, 1992). This iris was produced in a very interesting way. Mathes crossed a pure oncocyclus aril hybrid (I. iberica x I. auranitica) with the dwarf bearded species I. suaveolens. Both the aril and the dwarf are diploids (two sets of chromosomes), and wide crosses between diploids ordinarily produce sterile offspring. Mathes, however, used colchicine treatment to convert the seedling to tetraploidy (four sets of chromosomes). Theory predicts that such a tetraploid would be fertile, and indeed it was! (See my earlier blog post, Tetraploid Arils, Anyone?) Tetraploids created in this way can be unstable, reverting to the diploid state or growing poorly or erratically. So to preserve this breeding accomplishment, Mathes used the pollen of the tetraploid seedling on a conventional arilbred, 'Dresden Gold' (Foster, 1975). The result of that cross was 'Anacrusis'.

'Anacrusis' thus carries an unusual complement of genetic material. It has two sets of aril chromosomes, one from the oncocyclus hybrid Mathes had used, and one from 'Dresden Gold'. It has one set of TB chromosomes from 'Dresden Gold', and one set of dwarf suaveolens chromosomes. So it is a "halfbred", with two sets of aril chromosomes and two sets of bearded chromosomes, but with an important difference: one of the bearded sets is from the dwarf species I. suaveolens, rather than the TB ancestry found in most halfbreds. The aril species I. auranitica is also something different, not to be found in the ancestry of most halfbreds.  'Anacrusis', the result of this unprecedented combination of genetic material, is an arilbred median (20 inches in height) with the globular oncocyclus flower form, dark color, and a large black signal.

It is worthwhile to compare this with more typical arilbred medians, which come from crossing halfbreds with standard dwarf bearded irises (SDBs). These get their dwarf ancestry from I. pumila, whereas 'Anacrusis' gets its from I. suaveolens. Conventional arilbred medians are one-quarter aril, but 'Anacrusis' is one-half aril. And finally, conventional arilbred medians are sterile, but 'Anacrusis' is fully fertile, just like tall halfbreds are.

But what to cross it with? The first 'Anacrusis' child to be introduced was 'Invention' (Mathes, 1994), the result of crossing 'Anacrusis' with a sibling. This iris is similar to 'Anacrusis', also 20 inches in height, and with a similar dark color.

'Concerto Grosso' (Mathes, 1998) OGB/ABM

The next avenue to explore was combining 'Anacrusis' with other arilbreds. To this end, Mathes made use of one of his other unusual arilbreds, 'Gelee Royale' (Mathes, 1982). This iris is that most unusual of creatures, a pentaploid (five sets of chromosomes)! Its pod parent was an triploid OGB+ arilbred (2/3 aril complement, with the aril sets coming from I. auranitica and the Regelia I. hoogiana), with 'Dresden Gold' again as the pod parent. Although this is a complicated pedigree, 'Gelee Royale' breeds much like other halfbreds do. Mathes crossed 'Gelee Royale' with its sibling, crossed the result with the 'Anacrusis' sibling, and then finally crossed the result to 'Invention'. The result of this multi-generation hybridizing work was 'Concerto Grosso' (Mathes, 1998). Despite the presence of 'Gelee Royale' (registered at 35.5 inches) in its pedigree, 'Concerto Grosso' is still only 20 inches tall itslef.

'Concerto Grosso' has larger flowers than 'Anacrusis' and 'Invention', and is a rich mahogany color, quite different from most arilbreds. It went on to with the C. G. White medal, the highest award for arilbreds, in 2005.

'Iridescent Orange' (Mathes, 2001), OGB

Mathes had not finished his work with this line, however. 'Anacrusis', 'Invention', and 'Concerto Grosso' are all very dark in color, and Mathes wanted to extend the range of this line to lighter hues. 'Iridescent Orange' (Mathes, 2001) from ('Invention' x 'Gelee Royale') X 'Concerto Grosso' is a lovely orange self with a dark signal. At 23 inches in height, it is just above the limit for the arilbred median category, as defined in the Checklist of Arilbred Dwarfs and Medians. Its sibling, 'Suprassing Yellow' (Mathes, 2001) is a yellow rendition of the theme, also 23 inches.

The line is carried on in 'Glittering Garnets' (Donald Eaves by Elm Jensen, 2010) is from 'Anacrusis' crossed with the arilbred 'Desert Plum'. This is 22 inches in height, at the upper limit of the arilbred median category.

These irises have also been used in crosses outside the halfbred fertile family to which they belong. 'Dotted Sunsuit' (Mathes, 2001), is an OGB+ triploid from a yellow 'Anacrusis' sib crossed with an oncogelia seedling. 'Chain Reaction' (Tasco, 2007) comes from an SDB seedling x 'Concerto Grosso', a small arilbred median at 13 inches. 'Arcanum' (Jensen, 2013) is from 'Anacrusis' x I. pumila 'Crouching Tiger', a diminutive arilbred dwarf at only 6 inches in height!

There is still potential to be tapped from the 'Anacrusis' legacy. Its value in breeding fertile arilbred medians should be noticed and pursued. The most promising way to go about this is to cross 'Anacrusis' or any of its descendants with the smallest halfbreds available. 'Peresh' (Whitely, 2001), at 15 inches, and its siblings 'Eglon', 'Kedesh', and 'Tekoah' come to mind.

The creative, unprecedented cross that produced 'Anacrusis' is a true hybridizing success story, not only producing an interesting, attractive iris, but opening up new paths for the hybridizer and for others who were to follow.

Our debt to Iris aphylla

Tom Waters

I. aphylla

The European bearded iris species Iris aphylla has contributed to the development of modern bearded irises in a number of different ways. It still remains of considerable interest to hybridizers, particularly those working with the median classes.

The species is native to much of eastern Europe, with a range extending farther north than other bearded species. This makes it thoroughly winter hardy. It goes completely dormant in winter, losing all its leaves right to the ground. (The Latin word aphylla means "leafless".) The flowers are violet, although some recessive white and other off-color forms exist. The flowers themselves are not particularly glamorous, being often narrow and of poor substance. One of its most distinctive characteristics is prolific basal branching, with long branches starting low on the stalk, not infrequently at the point the stalk emerges from the rhizome. It varies in height, with forms as small as 30 cm and as tall as 60 cm or more. Both wild-collected forms and garden cultivars of the species have been registered and circulated.

I. aphylla 'Slick' (Lynn Markham, 2003)

Happily, I. aphylla has a similar chromosome complement to that of our modern tetraploid tall bearded (TB) and border bearded (BB) irises. This means it can be crossed with them to produce fertile seedlings that can be continuously worked with and improved for as many generations as one likes.

Early breeders showed little interest in medians, and simply worked I. aphylla into TB lines. It was found to contribute two interesting traits: an intensification of violet flower color, and blue or violet beards! Many early approaches to black in TB irises, such as 'Sable' (Cook, 1938) and probably 'Black Forest' (Schreiner, 1948), derive from I. aphylla. It is also behind many whitish or light blue TBs with blue or violet beards. In these irises, the dominant white found in TBs interacts with the intensification of violet pigment from I. aphylla.

When enthusiasm for median irises blossomed in the 1950s, with the formation of the Median Iris Society and the establishment of the four classes of median irises, creative breeders began to consider the potential of I. aphylla to add variety to these classes.

'Tic Tac Toe' (Johnson, 2010)
tetraploid MTB descended from I. aphylla

The most ambitious of such undertakings was Ben Hager's project to create tetraploid miniature tall bearded (MTB) irises. This class had been created with diploids in mind. Most TB irises from the 1800s and early 1900s were diploid, with a daintiness that was lost when tetraploids came to dominate. Early MTB breeders had taken these daintier TBs and bred them for even smaller size and greater delicacy. The MTBs were promoted as subjects for flower arranging. Tetraploid TBs, however, showed more different colors (such as tangerine pink), wider form, and better substance. Could these traits from the modern TBs be transferred to irises dainty enough to qualify for the strict requirements of the MTB class? Hager set about proving that they could. He crossed I. aphylla with small TBs and BBs, and then kept breeding toward the MTB requirements. After many generations of work, he established a line of tetraploid MTBs. Although these did not look exactly like the diploid MTBs (I. aphylla yields straight, upright stalks with vertical branching, whereas diploid MTBs often have a more zig-zag branching style), they had an appeal all their own. The first pink MTBs were Hager's tetraploids from I. aphylla.

'Saucy' (Craig, 1998)
tetraploid IB descended from I. aphylla

Hager's work was carried on by Jim and Vicki Craig, who combined Hager's irises with their own crosses involving different forms of I. aphylla. They introduced not only tetraploid MTBs, but BBs and IBs from the same breeding lines. This enhanced the variety of all three classes. They even produced a couple that were small enough to qualify as standard dwarf bearded (SDB)!

Others have worked with I. aphylla over the years, and continue to do so. Some hybrids that a relatively close to the species itself have been registered in the SPEC-X category. Paul Black's "small-flowered TBs" owe a debt to I. aphylla.

This species has contributed a great deal to the variety we find in both TBs and medians today. Do you grow any irises with I. aphylla ancestry? I'd wager you do!

'Night Mood' (Lynn Markham, 2003)
SPEC-X from 'Blackbeard' X I. aphylla 'Dark Violet'

Arilbred Irises: A Little History

Tom Waters

'Brash and Bold' (Black, 2009),
William Mohr medal 2106
(arilbred median)

The story of arilbreds begins in the late 19th century, when the exotic aril iris species of the Middle East found their way into the gardens of European plant enthusiasts. Sir Michael Foster, England's foremost iris expert at the time, tried his hand at crossing the arils with the more familiar tall bearded (TB) irises. His motives were mainly exploratory; at the time, no one knew if the arils and bearded irises were compatible, or whether desirable garden plants might result from crossing them.

Although these early arilbreds were interesting plants, showing features of both parents, they were also quite sterile. Arils and TBs were just too distantly related to produce fertile offspring when crossed. One might expect hybridizers to simply give up on the idea, but many kept trying. The allure of the arils, with their huge globular blooms, often strikingly marked with velvety signals, veins, and stippling, was not something to be lightly set aside. Also, the arils themselves were difficult to grow in England and much of the US, demanding very dry conditions when dormant in summer and winter. So the great hope was that crossing arils with TBs could produce an aril-like bloom on a plant that could grow in any garden where TBs grow.

The famous iris breeder William Mohr, working in California, produced an arilbred iris that seemed close to fulfilling this dream. Named for him posthumously in 1925 by his friend and fellow iris expert Sidney Mitchell, the iris 'William Mohr' was an instant sensation. Its large blooms and wide falls, inherited from its aril parent Iris gatesii, proved irresistible in an era when most TBs had relatively small, narrow flowers.

'Elmohr'

Like the other arilbreds of similar pedigree, 'William Mohr' was essentially sterile. But it was so popular that hybridizers all over the country kept making crosses with it, ever hopeful. And occasionally 'William Mohr' would reward such persistence by producing a seed or two. We now understand that these seeds were the result of unreduced gametes, where an ovule is produced by bypassing the normal cell division. Usually it was TB pollen used in making these crosses, so the resulting seedlings were 1/4 aril. 'Mohrson' and 'Grace Mohr' were the first introduced, in 1935, launching a tradition of working "Mohr" into the name of these arilbreds. One of these, 'Elmohr' (P. A. Loomis, 1942) became the first and only arilbred to win the Dykes Medal. In this way, William Mohr became associated with the "quarterbreds" (arilbreds of 1/4 aril ancestry), even though he himself never produced any irises of this type.

Although less widely appreciated than the famous 'William Mohr', there was actually one truly fertile arilbred in cultivation at this time, 'Ib-Mac' produced by the Dutch firm of Van Tubergen and introduced in 1910. Unreduced gametes were once again involved, as its aril parent Iris iberica produced an ovule will two sets of aril chromosomes instead of the usual one. 'Ib-Mac' thus ended up as a balanced tetraploid, with two sets of aril chromosomes and two sets of bearded chromosomes, a configuration that is usually fertile.

Crossing 'William Mohr' with 'Ib-Mac' produced the fertile arilbred 'Capitola' (Frank Reinelt, 1940). Many hybridizers now began using 'Capitola' pollen on TBs, a much surer way to produce quarterbreds than hoping for the occasional seed from 'William Mohr'. These quarterbreds were also colloquially referred to as "Mohrs".

The frustration for hybridizers of this era was that although one could produce quarterbreds by crossing 'William Mohr', 'Ib-Mac', or 'Capitola' with TBs, there was no easy way to get more arils into the mix. The quarterbreds only showed moderate aril characteristics, and did not go very far in capturing the appeal of the aril species themselves.

'Oyez'

The great breakthrough in arilbred breeding came from the work of Clarence G. White in the 1940s. Based in southern California, he was able to grow many pure arils and use them extensively in his hybridizing. His early hybrids, such as the perennially popular 'Oyez' (White, 1938), were infertile diploids, but eventually fertile arilbreds began to appear among his seedlings. The first to be introduced was 'Joppa Parrot' (White, 1948). In the decade that followed, a steady stream of fertile arilbreds in a remarkable range of colors and patterns issued from White's garden. We do not know exactly how this happened, because by this time White had given up on keeping records of his crosses, claiming it took too much time away from making the actual crosses. Most likely it was the sheer volume of his breeding program that made these breakthroughs possible. With an enormous number of seedlings, even unlikely events such as unreduced gametes are bound to happen from time to time. The fertile C. G. White arilbreds were later shown to be balanced tetraploids (like 'Ib-Mac' and 'Capitola') with two sets of aril chromosomes and two sets of TB chromosomes.

The 1950s saw the founding of the Aril Society International (ASI). Despite the name, its membership was largely concentrated in southern California, with a few in New Mexico and elsewhere. The ASI in its early years provided a much-needed framework for defining the arilbred class and encouraging the breeding of arilbreds with clear, strong aril flower characteristics. To be classified as an arilbred, an iris could have no less than 1/4 aril ancestry. Hybridizers had often crossed the early quarterbreds back to TBs, sometimes for several generations, promoting the progeny as "arilbreds", although their aril genes had in most cases dropped by the wayside, leaving plants that were for all intents and purposes just TBs. The ASI cooperated with the American Iris Society to establish the C. G. White award for best arilbred in 1961. In 1969, the William Mohr award was added for arilbreds of less than 1/2 aril ancestry, restricting the C. G. White award to those that are 1/2 or more aril. This further encouraged hybridizers to focus on arilbreds with strong aril characteristics. Both these awards attained medal status in 1993.

With the "fertile family" of C. G. White arilbreds firmly established, arilbred breeding at last came into its own. As breeders continued to work with these fertile arilbreds, they improved both in gardenability and in the form, color, and pattern of the flowers themselves. The original C. G. White hybrids typically had only a small diffuse signal patch, and veining that was indistinct and blended. Through the extended effort of dedicated arilbred hybridizers, we now have arilbreds with huge, dramatic signals, striking crisp veining, and an extraordinary range of bright clear colors.

'Anacrusis'

Most fertile arilbreds today derive almost entirely from the original C. G. White introductions. A few notable additions to the family appeared subsequently: 'Welcome Reward' (Sundt, 1971), Henry Danielson's fertile regeliabreds such as 'Genetic Artist' (Danielson, 1972), and Harald Mathes's fertile arilbred medians beginning with 'Anacrusis' (Mathes, 1992). Fertile arilbred seedlings produced by Samuel Norris from his tetraploid arils crossed with TBs also appear in the pedigrees of some modern arilbreds.

The fertile "C. G. White type" arilbreds have also opened up other new areas of arilbred breeding. Crossed with TBs, they have given us quarterbreds that are much more aril-like than the old "Mohrs", and crossed with the standard dwarf bearded (SDB) irises, they have produced the charming arilbred medians, which are at least as popular as the taller quarterbreds today.

The history of arilbred breeding has progressed from an early period of difficulty and frustration, through the breakthrough of C. G. White's "fertile family" to a modern era of continual improvement and expanding diversity. What will the future bring?

Honey, I Shrunk the Irises!

by Tom Waters

MTB irises 'Redrock Princess' and 'Dividing Line'

Miniature Tall Bearded?

An oxymoron is a phrase whose parts seem to contradict each other, like jumbo shrimp. In the iris world, we have the rather perplexing term miniature tall bearded. How can an iris be both tall and miniature? Of course the word "miniature" here must be taken in a relative sense: these are irises much smaller than the standard tall bearded irises which they otherwise resemble.

Bearded irises are categorized into six classes, based mostly on height. Strangely, however, there are three classes that all occupy the height range between standard dwarfs and tall beardeds: intermediate bearded (IB), border bearded (BB) and miniature tall bearded (MTB). When I first became interested in irises in southern New Mexico in the 1970s, I found this rather confusing, moreso because at the time I had not grown any of these various types of medians. I asked a local club member about MTBs, and she said "I don't think anyone here grows those."

Happily, this group of irises has grown steadily in popularity since then. They are now widely grown, and one 'Dividing Line' (Bunnell, 2005), has even won the Dykes Medal. But what are they exactly?

The Story of MTBs

The answer takes us back to the 1920s and 1930s, when the popular tall bearded irises were changing rapidly through the work of the hybridizers of the day. In particular, more and more tetraploids were being introduced and supplanting the older diploids in popularity. A tetraploid is a plant with four sets of chromosomes, whereas diploids have only two. Tetraploids are often larger and huskier than their diploid counterparts. This was certainly the case with the TB irises, and the iris world was all enthused over the new large blooms and tall stalks.

'Hot News'

But there were a few people here and there who were less enthusiastic about the new "bigger is better" trend. Ethel Peckham, Thura Hires, and Mary Williamson were amongst the first to go against the trend and seek out the smallest TBs, rather than the largest. Mary Williamson's father, E. B. Williamson, was a noted iris breeder at the time, and the three ladies kept a close eye on his seedling beds looking for the daintiest, tiniest irises, which the hybridizer himself referred to as "runts". Pekham dubbed them "table irises" to call attention to their suitability for flower arrangements. These original selections were all diploids.

Interest in the table irises declined as time passed, however, probably because they were not recognized as an official category, so had no awards or other encouragement. They might have been altogether forgotten were it not for the work of Alice White in the 1950s, who tirelessly promoted the table irises. The timing was right, as this was an era when there was a surge of interest in dwarf and median irises. New types were being developed, and it became apparent that a new system of categories was needed to accommodate the many different sorts of irises smaller than the TBs. So in 1957, the miniature tall bearded class was created. This name was chosen over "table irises" to emphasize that they can be appreciated as garden plants in their own right, not just for flower arrangements.

The requirements of the MTB class are stricter and more exacting than any other. Not only must they fall in the proper height range (41 to 70 cm, although the center portion of that range is preferred), but they must also meet limits for flower size and even stem diameter. In many ways, the standards of the class are a reaction against the prevailing trends in TB breeding. Instead of taller and taller stalks with larger and larger blooms, MTBs must be truly miniature and dainty in all respects.

Meet the Diploids...

Iris variegata

As noted above, the original MTBs were all diploids. That is no longer the case, but diploids remain the most prominent type. Although a variety of different bearded species are in the background of the diploid MTBs, the dominant influence is from Iris variegata, a dainty median-sized species from eastern Europe, usually yellow with red or brown veins covering the falls. Its wiry stems curve gracefully, resulting in a slightly zig-zag branching pattern. The blooms have a nice flaring form.

There are many modern diploid MTBs in which the variegata coloring and form are much in evidence, but the range of color and pattern goes beyond that into white, blue, violet, plicata, orchid, and blends. Some recent favorites of mine include 'Redrock Princess' (Witt, 2006), 'Peebee and Jay' (Schmieder, 2006), and 'Hot News' (S. Markham, 2009). 

diploid MTB 'Rayos Adentro' (Morgan, 2007)

...and the Tetraploids

Iris aphylla

Although the tetraploid TBs are larger than the diploid TBs, there are tetraploid bearded species in all different sizes. Early on, some creative hybridizers such as Ben Hager realized that it might be possible to breed tetraploids that would meet the strict size requirements of the MTB class. Hager used Iris aphylla, a copiously branched small bearded species to create tetraploid MTBs, introducing many in the 1970s and later.

Why undertake such a project? One reason is that there are colors and patterns in the tetraploid bearded irises that simply do not exist in the diploids. Tangerine pink is the best-known example. If you want a true pink (or orange, or red-bearded white) MTB, it will have to be tetraploid.

Iris aphylla has lots of branches and lots of buds, which is a good thing, but it brings some problems, too. The stems tend

'Tic Tac Toe'

to be stiff, with branches from the base of the stalk that stay parallel to the main stem. This can lead to a crowded, coarse appearance far from the MTB ideal of grace typified by diploids from Iris variegata. Still, with diligence and patience, the difficulties were gradually overcome, and today we have quite dainty and graceful tetraploid MTBs to complement their diploid counterparts.

Some favorites of mine include 'Say Red' (Craig, 2008), which has three buds in each of its many sockets, and seems to just keep on blooming forever, 'Tic Tac Toe' (Johnson, 2010), a lovely pink and pastel violet bicolor, and my new favorite 'Silver Ice' (Black, 2013) an almost-white plicata with beautifully formed ruffled blooms.

'Say Red'

Although some were initially skeptical regarding tetraploid MTBs, there is no doubt now that they are here to stay, giving us even more choices and possibilities within this class of delicacy, daintiness, and refinement.

Have you tried MTBs in your own garden? Do you prefer diploids or tetraploids, or do you enjoy some of each?

The Untapped Potential of Iris reichenbachii

by Tom Waters

Today's post is all about an underappreciated bearded iris species, Iris reichenbachii. The name, it seems, is bigger than the iris itself. I. reichenbachii is a dwarf, ranging in height from 10 to 30 cm (4 to 12 inches), with one or sometimes two buds at the top of the stalk. (Very rarely, a third bud may appear further down the stalk.) The flowers are yellow (often with brownish markings or blending), smoky violet, or occasionally clear deep violet.

Iris reichenbachii

The species is native to the Balkan peninsula, from Rumania and Bulgaria through Serbia and into Greece. A related species, I. suaveolens, is similar but smaller. Two other species names, I. balkana and I. bosniaca, are now regarded as synonyms of I. reichenbachii.

As a garden subject, I. reichenbachii is pleasant enough, if somewhat unremarkable. It has found a home with rock gardeners and plant collectors. For those who fancy modern hybrid dwarf and median irises, this little species can seem drab by comparison. The petals are rather narrow, substance is lacking, and the colors can seem a bit murky.

To the hybridizer, however, I. reichenbachii has something unique to offer. Its chromosomes are very similar to those of tall bearded irises, and it is quite compatible with them. Furthermore, I. reichenbachii exists in both diploid (two sets of chromosomes) and tetraploid (four sets) forms. Since modern TBs and BBs are tetraploid, they can cross with tetraploid I. reichenbachii and produce fertile offspring. (For an explanation of diploids and tetraploids, see my earlier blog post Tetraploid Arils, Anyone?)

'Progenitor' (Cook, 1951)
 from I. reichenbachii X TB 'Shining Waters'

In the 1940s, the talented hybridizer Paul Cook did precisely that. A seedling from the cross, aptly named 'Progenitor', was registered in 1951. It was an unimpressive iris of intermediate size, but Cook could see its potential. 'Progenitor' was a bicolor, with violet falls and pure white standards. At the time, this was a new color pattern. (Earlier bicolors were actually variations on a "spot pattern" from I. variegata, and seldom showed the completely solid falls and pristine standards of 'Progenitor'. It is interesting to note that I. reichenbachii itself is not a bicolor. The bicolor pattern resulted from combining its genes with those of the TB parent. By crossing 'Progenitor' back to high-quality TBs, Cook was eventually able to transfer the bicolor pattern onto irises that otherwise showed no resemblance to the modest little dwarf that had given rise to the new pattern. 'Whole Cloth' (Cook, 1958), four generations on from 'Progenitor', won the Dykes Medal in 1962.

Virtually all TB and BB bicolors today (standards white, yellow, or pink; falls blue, violet, purple, reddish, or brown) are descendants of 'Progenitor', and hence of I. reichenbachii.

But there is still more to be done with this interesting little species. When Cook was making his crosses, there was very little interest in dwarf or median irises. In fact, medians as we know them today hardly existed at that time. So Cook simply worked to transfer the new color pattern into TBs. Today, however, there is considerable interest in breeding medians, especially BBs and MTBs that are consistently small and dainty. Surely the little dwarf I. reichenbachii has something to offer in these endeavors. The tetraploid forms are compatible with BBs and tetraploid MTBs, while the diploid I. reichenbachii could be crossed with diploid MTBs. Since these sorts of crosses should produce fertile seedlings, a hybridizer could continue the breeding line to achieve any desired goal.

Iris reichenbachii

I. reichenbachii is a little difficult to find in commerce, but not impossible. Some specialty nurseries list it, and if one is willing to grow from seed, it shows up rather often in seed exchanges that include iris species.

If you see this odd little species available somewhere, why not give it a try? Perhaps even make a cross or two to see what happens...

Tetraploid Arils, Anyone?

by Tom Waters

'Tadzhiki Eclipse'

If you're a gardening enthusiast with a keen interest in irises or other perennials, you've probably come across the term tetraploid. There are tetraploid daylilies, for example, and in the iris world you'll see the term used to describe some miniature tall bearded (MTB), Siberian, and other types of iris. But what is a tetraploid and why does it matter if a variety is tetraploid or not?

Plants and animals are made up of cells, and in the nucleus of each cell are structures called chromosomes that carry the organism's genes. These chromosomes come in sets. For almost all animals and many plants, there are two sets of chromosomes in each cell. Humans, for example, have two sets of chromosomes, 23 in each set. At conception, each person receives one set of chromosomes from their mother and one from their father. One can't really think of any simpler way for an organism to inherit genes from both parents.

There are more complicated ways, however, especially in the plant kingdom. Some plants have four sets of chromosomes, two sets coming from each parent instead of one. These are tetraploids. (Plants with just two sets are called diploids.)

What are the consequences of having four sets of chromosomes instead of two? One consequence is that tetraploids are frequently (not always) larger than their diploid counterparts. In the 19th century, garden tall bearded irises were all diploids. Around 1900, plant collectors found tetraploid tall bearded species in the Middle East, and brought them into European and American gardens. The new plants attracted attention because of their taller stems and larger flower size. (There was no knowledge of chromosome numbers at the time, so iris growers and breeders were aware only of the difference in appearance of the new plants.)

The tetraploids were so popular with iris breeders that by the middle of the twentieth century, virtually all new TB varieties were tetraploid. This is still the case today.

One must be cautious, however, in associating tetraploids with large size. Size is determined by many factors. One of the very smallest bearded irises, the dwarf species Iris pumila, is a tetraploid although the blooms are only a few inches above the ground!

The great importance of tetraploidy in plant breeding is not that tetraploids are sometimes larger, but rather that more genetic combinations are possible with tetraploids than with diploids. With four copies of every gene instead of two, there are just many more possibilities!

One extraordinary aspect of tetraploid breeding is that hybrids between different species or types may be fertile if the parents are tetraploid, but sterile if the parents are diploids. The standard dwarf bearded irises (SDBs), for example, are fertile hybrids between tetraploid TBs and the tetraploid dwarf Iris pumila. So tetraploidy makes possible whole new types of fertile hybrids that simply could not exist otherwise. This is the main reason some hybridizers have taken such an interest in tetraploids.

'Bronze Beauty Van Tubrgen'

So now we come to the topic of this post: tetraploid arils. I love aril irises, with their exotic color patterns and dramatically shaped blooms. Most aril species are diploids. (I'm referring to pure arils here, not the arilbreds, which are a mix of aril and bearded ancestry.) In fact, the oncocyclus arils (the type that usually comes to mind when one thinks of arils) are all diploid. Crossing them with bearded irises, when it can be done at all, produces sterile hybrids.

Think of the possibilities that could open up if there were a family of tetraploid arils, like the family of tetraploid TBs!

Aril hybridizers have been thinking of that possibility for decades, and there are in fact some tetraploid arils, just not very many yet.

First, although all the oncocyclus species are diploids, there are two Regelia species that are natural tetraploids: Iris hoogiana and Iris stolonifera. A classic hybrid from these two species, 'Bronze Beauty Van Tubergen' (Van Tubergen, R. 2001) is also tetraploid. These are all lovely irises, but being Regelias, they do not have the oncocyclus characteristics, like huge globular blooms and big velvety black signals, that are the allure of aril irises for most people.

'Dunshanbe'

Second, a few arils with some oncocyclus ancestry are "accidental" tetraploids. Occasionally, a diploid parent produces a tetraploid seedling by chance. 'Persian Pansy' (Austin, 1960) and 'Tel Hashi' (Kellie, 1968) came about this way, but both seem to be lost now. 'Dunshanbe' (Wilkes, 1977), a seedling of 'Persian Pansy', is still being grown however, and is quite lovely with a dark sheen and nice veining. Its makeup is still more Regelia than oncocyclus, however.

Third, some breeders have created tetraploids deliberately using the chemical colchicine, that interferes with cell division, sometimes converting a diploid plant to a tetraploid. Usually, the plants created this way are unstable and sometimes unhealthy, but they can be crossed with other tetraploids to produce stable, reliable plants. 'Werckmeister's Beauty' (Werckmeister, 1992) came from this approach. In the 1980s, Sam Norris and John Holden created many tetraploid arils of predominantly oncocyclus makeup using this method. Alas, few have survived to the present day, and none are available commercially. Lawrence Ransom used one of these to produce 'Tadzhiki Eclipse' (Ransom, 1997) and 'Tadzhiki Bandit' (Ransom, 1997), both of which are still being grown in Europe and the US. 'Tadzhiki Eclipse' is, I think, the most oncocyclus-like tetraploid aril one is likely to be able to acquire today.

'Werckmeister's Beauty'

Through a little patience and diligence, I have acquired a small collection of tetraploid arils from the plant sale of the Aril Society International, occasional offerings of commercial growers, and the generosity of fellow aril hobbyists. I encourage others to do the same, especially those who live in the western US or other regions where pure arils can be grown without heroic measures being taken on their behalf. These are arils, not arilbreds, so they may need a little special attention regarding soil and siting. I have found them easier than most other pure arils, however.

If you are a hybridizer, you can cross them with each other to expand the family, or cross them with tetraploid bearded irises to create brand new types of fertile arilbreds.

Even if you are not a hybridizer, you can enjoy their bloom and know that you are helping preserve a very important group of plants, which may someday become the progenitors of new breeds of irises we can only imagine today.

If you can grow aril irises, have you tried any of the tetraploids? I think they are worth seeking out.

'Tadzhiki Bandit'