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'

Growing Irises from Seed

by Tom Waters

We usually propagate irises by division: digging up a large clump, breaking apart the individual rhizomes, and replanting. This method is easy, and because most irises increase rapidly, within a few years you will have plenty of them. This post is about a different way of propagating irises: planting seeds. This is a process that has some challenges, but also has some wonderful rewards. If you've never thought about growing irises from seeds, or have wondered about it but are unsure how to start, read on!

Why?

If you are hybridizing, you will necessarily be growing irises from seed. Hybridizing refers to cross-pollinating irises to produce new varieties. When you cross two different irises, the result is a pod of seeds. Each of the seedlings will grow into a new individual, not exactly like any other iris. Propagating by division only creates exact copies of the original plant, whereas progagation from seed creates only brand new plants, different from either parent. Even if you are not intending to embark on serious hybridizing program to create new varieties to sell commercially, making crosses and raising seedlings can be fun and interesting.

Woohoo! Iris seeds just arrived from Czechia

But hybridizing is not the only reason you might want to raise irises from seed. Some types of irises may just not be obtainable from commercial growers as plants, but you may be able to acquire seeds from a collector or from a seed exchange. This is especially true of iris species, the wild irises from different parts of the world. It can be very difficult to import live plants from other countries, but importing seeds is usually much easier. I've gotten seeds of iris species from collectors in the Czech Republic and from seed exchanges run by the Species Iris Group of North America (SIGNA), the British Iris Society (BIS), the Scottish Rock Garden Club (SRGC), and the North American Rock Garden Society (NARGS). Although the seedlings from a given offering of species seeds will all be different, in subtle or obvious ways, they will all still be plants of that named species, unless the person providing the seed misidentified the plant, or unless it was accidentally cross-pollinated by a different species growing nearby.

Growing irises from seeds also has some other advantages: you get a wide variety of different plants, so you can choose the ones that do best in your climate or whose appearance you prefer. Growing from seed is also a way to eliminate virus infection, should that be a problem.

Finally, growing irises (or any plant) from seeds is a very satisfying experience. It connects you with the whole process of growth, from its very beginning. There's nothing quite like seeing the first bloom of a plant you've grown from seed yourself.

How?

The process of growing irises from seeds is not (usually) very difficult, but it does require patience and attention to factors that you might not have considered if your only experience of raising plants from seeds is growing vegetables or annuals. There have been many articles written on special ways to grow iris seeds; you can find a number of them on the web. In this post, I am not going to suggest one particular method as superior, but just give you an overview of the basics, so that you can get started and learn what works for you.

There are two requirements for germinating iris seeds:

1. They must experience several months of cold temperatures, followed by a warming period.

2. They must have adequate moisture.

Seeds planted into pots sunk in the ground
 (gravel on top protects from washout
and animal interferenece)

The simplest way to meet these two requirements is to plant the seeds outdoors in the autumn or early winter, and let nature take its course--assisting with supplemental water if natural precipitation is insufficient. Seeds can be planted straight in the soil, or in pots sunk into the ground or just left on a porch or in a cold frame. A planting depth of 1 cm or 1/2 inch is suitable for most seeds. Germination usually occurs around the time of iris bloom in the spring.

Some growers prefer to give the seeds their cold treatment ("stratification") indoors, by putting the seeds in baggies with slightly moist vermiculite, perlite, or other sterile medium and refrigerating them for 60 days or more. The advantage of indoor stratification is greater control over the conditions, and the possibility of getting germination a few months earlier. The disadvantage is that you need to be prepared to grow on the seedlings indoors under grow lights for some time, until they are ready to be hardened off and planted outdoors.

Newly sprouted seedlings!

I prefer the outdoor method, as it is less bother and easier to manage with large numbers of seedlings. If I had an extra refrigerator to use for seeds, I might prefer indoor germination.

Whatever method is used to germinate the seeds, they should be transplanted to a semi-permanent seedling bed outdoors when they have at least three leaves. Some may bloom a year later. The year after that, most should bloom and you can decide which ones to keep and which to discard.

The reason the period of cold temperature is needed is that irises, like many perennials from temperate climates, cannot easily survive a winter while still small seedlings. When germination occurs in the spring, rather than in the fall, the young plants have the best possible chance of survival. In contrast, most annuals are fast-growing, opportunistic plants that can grow, flower, and produce seed whenever there is a few months of warm weather.

Dormancy

Even if the requirements above are met, not all the seeds will sprout the first year. With garden variety bearded irises, the percentage will usually be more than 50%, and can approach 100%. Most of the remainder will sprout the following year. At the other extreme, aril irises may sprout a few at a time over a period of 10 years or more. Why is this? It is nature's "insurance policy" against calamities and harsh conditions of various sorts. If all seeds sprouted at the same time, a drought, flood, fire, or other disaster could destroy the whole population. By having the seeds sprout over the course of several years, it is virtually guaranteed that some will survive.

For the gardener, however, such protracted dormancy is a frustration. Few of us want to wait a decade for the seeds we plant to sprout! In irises, dormancy has at least two causes: the hardness of the seed coat, which makes it mechanically difficult for the seedling to emerge, and chemical germination inhibitors inside the seed itself. In nature, the action of water and the cycles of freezing and thawing serve to gradually weaken the seed coat and to leach away the chemical inhibitors.

Some growers have success by planting seed fresh, before it has a chance to dry out. For some types, at least, this can bypass dormancy and result in immediate germination. Of course, one then needs a way to care for the seedlings over winter.

A variety of techniques are used to overcome dormancy artificially. One can attempt to leach out the germination inhibitors by prolonged soaking or use of running water. One can overcome the hard seedcoat by abrasion or chipping (cutting away the seedcoat to expose the embryo). This "forced germination" procedure is often recommended for difficult oncocyclus seeds. The ultimate procedure is to excise the embryo under sterile conditions, and germinate it on a nutrient agar medium. This "embryo culture" can be used to germinate seeds that will not germinate any other way, but it is very demanding work and the young seedlings are very vulnerable.

Whether you choose to use any of these techniques for overcoming dormancy will depend on whether the basic method is giving adequate germination for the types of seeds you grow. I think the best advice is to try natural germination first, and then move on to progressively more invasive and difficult techniques if you need to.

The Payoff

I encourage everyone to trying growing irises from seeds at least once, whether it's making a cross or two in your own garden or ordering a packet of seeds from a seed exchange. It's an adventure, and the first bloom of an iris you've raised from seed yourself makes it all worth the wait!

Here are three seedlings from the same cross, arilbred 'Aztec Prince' (Tasco, 2009) X Iris pumila:

Winter Iris Gardening

by Tom Waters

This being the day after Christmas, it seemed appropriate to write something "seasonal" for this blog post. So what does winter mean for the iris grower?

A word to the wise: Iris growers live in many, many different climates. What is true in one climate may be false in another. Be suspicious of any gardening advice on such topics as winter care that is written as though it applies everywhere. In this post, I'll mention a few things that one might want to consider, but I do not offer any absolute advice. For that, you need to speak with other gardeners in your own area or just do some trial-and-error work on your own.

All irises grow in temperate climates. They are adapted to the changing seasons. Most kinds have periods of rapid growth in spring and autumn, but slow down or go dormant in summer and winter. In fact, irises need a distinct winter with cold temperatures in order to bloom; they will not do well in tropical climates.

Selecting irises for your winter conditions. All garden irises are ultimately derived from wild iris species from different parts of the northern hemisphere. The climate where those species live can tell you something about how those irises will do in various climates. Louisiana irises, for example, are native to the southeastern US, where winters are mild and summers are warm and wet.

Among the bearded irises, winter hardiness varies a great deal. The original diploid tall bearded irises come from the species Iris pallida and Iris variegata, native to central Europe, often at rather high altitudes. They have little difficulty surviving cold winters. These diploid types are today mostly found among the miniature tall bearded (MTB) irises. Modern tetraploid tall bearded irises also have species from the eastern Mediterranean in their ancestry, meaning that some of them fare poorly in colder climates. Depending on the particular mix of genes, modern TBs can be utterly hardy or quite tender, or anything in between. So how is one to know? Checking with other growers in your own area is always good advice, but one can also take a clue from the region where the iris was originally hybridized. Irises bred in Canada or in the US midwest are almost certain to be suited to cold winters, while those from the Pacific coast are not necessarily so. Border bearded irises (BBs) have the same ancestry as TBs, and so the same considerations apply.

Among the dwarf and median classes, miniature dwarfs (MDBs), standard dwarfs (SDBs), and intermediates (IBs) virtually all have Iris pumila in their ancestry. This tiny species is a native of central and eastern Europe, growing at higher elevations and in more continental climates than most of the TB species. It is very hardy, perhaps to a fault, because it has a reputation for failing to grow and bloom well in climates with mild winters. Consequently, growers in places like southern California and Arizona sometimes find that these types (the MDBs especially) do not do well for them.

Arilbreds vary in their degree of winter hardiness. The aril species grow in southwestern and central Asia. Although some of these are adapted to the very warm climate of the deserts of Israel, Jordan, and Syria, most arils are in fact mountain plants used to extreme winter cold and extreme summer heat. So why do northern growers find many arilbreds too tender for their climates? The fault is probably in their TB ancestry. The center of early arilbred breeding was Southern California, and the TBs used in arilbred breeding were those that did well in that mild-winter climate.

Having made these generalizations, I encourage iris growers to experiment with types that "conventional wisdom" might recommend against. Every garden has microclimates, and every category of irises has cultivars that are surprisingly adaptable.

Winter care: mulching. Irises are not very different in their needs from other perennials you may grow, so in climates where winter mulch is beneficial, it can be applied to iris plantings as well. The main purpose of a winter mulch is not to keep the plants warm, but to moderate the cycles of alternate freezing and thawing that can push plants out of the ground expose them to risk of winter rot. Snow makes an excellent insulator. If your climate is such that you can count on a fairly thick cover of snow all winter long, you have the ideal natural winter mulch!

I am not so fortunate here in northern New Mexico. We get temperatures below 0 degrees Fahrenheit every winter, most often without any snow cover at all. I do not apply a heavy much, but I do allow garden debris to stay in place over winter, giving the crowns of the plants some buffer against the wind and cold. I also put down a layer of cotton bur compost in the late autumn. Winter weather gradually degrades it and incorporates it into the soil, but in the meanwhile it seems to offer a little protection.

Beware that mulches can harbor overwintering insect pests and can collect water. In climates where these are issues of concern, it is best to forgo mulch.

Winter care: water. In climates where the ground freezes, watering in winter is nor desirable, and often not even possible, so winter offers relief from this particular garden duty. Many gardening books seem to assume this is true everywhere. However, if you live in a dry climate with spells of warm weather during the winter, you should pay attention and provide a little supplemental water as needed to keep the garden from becoming totally desiccated. Not much is needed: remember that the plants are dormant or semi-dormant, and that evaporation is less because of the cool temperatures.

Seeds! For those of us who like to grow irises from seeds, winter is an important time. Like most temperate perennials, irises have seeds that resist germination during the winter, to sprout when spring arrives. The cold and wet of winter are actually part of the preparation they need to germinate. The simplest way to grow irises from seeds is to plant them outdoors in the autumn, where they can overwinter and come up the following spring. Nature is unpredictable, of course, so many people prefer to use an indoor refrigeration process to replicate winter conditions. I'm not really set up for that kind of project, so I plant mine outdoors and let nature do her work.

Seeds from my own crosses get planted around the time of the first frost in autumn. Those I get from seed exchanges or other providers usually come later, in December or January. The longer they have to experience the winter wet and cold, the better. Since winter and spring weather here is erratic, germination is unpredictable. I generally leave the seeds in place for several years.

I hope I've touched on at least a few topics of interest. What are your own experiences of irises and winter?

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...

Iris pumila: a Tiny Treasure

by Tom Waters

Iris pumila

In an earlier blog post, I wrote about how the tiny bearded iris species Iris pumila was imported to the US by Robert Schreiner in the 1930s and crossed with the popular tall bearded irises, giving rise to a whole new type of garden irises, the standard dwarfs (SDBs).

Today, I thought I would write about Iris pumila itself. Besides being an extraordinary find for iris hybridizers, it is a delightfully varied species that makes a wonderful garden plant. It is invariably the first bearded iris to bloom in the spring, starting several weeks before most of the hybrid dwarf cultivars.

In the wild, Iris pumila grows in a wide range across eastern Europe, from Austria in the west through Hungary, Romania, Ukraine, and into the Caucasus Mountains as far as Armenia and even Turkey. It is often found at higher elevations and dry, continental steppe climates. It is adapted to cold winters and sunny, open spaces. Conventional wisdom has it that Iris pumila does best in areas of colder climate (USDA hardiness zone 6 or colder), although I have grown it in southern New Mexico (zone 8), so it may be worth a try even in warmer areas.

Iris pumila is among the tiniest of bearded irises, with the tip of the blooms only about 10 cm from the ground. Usually, the stem is so short as to be hardly detectable; the blooms are held aloft on an elongated perianth tube, so that each bloom seems to be just sitting atop the rhizome from which it grows.

The species shows a phenomenal range of color. To judge from pictures I have seen on the internet, Ukraine seems to be the center of its diversity, with many extraordinary color combinations seldom seen in plants that have been imported to the US or western Europe.

The basic color may be blue, purple, yellow, or white, in any shade from pale to intensely saturated. There is almost always a darker "spot pattern" on the falls, which may be small or may cover virtually the entire petal. The spot may be solid color, or appear as rays or veins or an uneven wash of color.

You can find Iris pumila offered for sale by some alpine or rock garden nurseries. (A word of caution: non-specialist nurseries, like garden centers, often use "Iris pumila" to label any small bearded iris cultivar; these are not the true species.) Many seed exchanges have it, and growing from seed can be extraordinarily fun, since every seedling is different. It does take some patience, however, as irises take 2 to 3 years to bloom from seed.

There are also named cultivars of Iris pumila available from specialty iris growers. Many of these are registered as miniature dwarf bearded (MDB), since they meet the definition of the class. More recently, some have been registered as species (SPEC). One very popular Iris pumila cultivar is 'Little Drummer Boy' (Willott, 1997), which won the Caparne-Welch Medal for best MDB in 2005.

'Little Drummer Boy' (Willott, 1997)

Some newer Iris pumila cultivars include 'Steppe' (J. Burton, 2011), 'Keystone Oracle' (Jesberger, 2011), 'Wild Whispers' (Coleman, 2012), and 'Royal Wonder' (Coleman, 2013). 'Keystone Oracle' is notable for turquoise tones around the beard and spot, which varies from dark to pale depending on climate.

'Keystone Oracle' (Jesberger, 2011)

'Hobbit' (Miller, 2004)

'Royal Wonder' (Coleman, 2013)

I hope I've given you a taste of the beauty and variety of this diminutive iris species. Have you tried growing any Iris pumila in your own garden?

The Evolution of Irises

by Tom Waters

Have you ever wondered where irises come from? Well, we all know they come in a box from Oregon via UPS. But I mean a little farther back than that. How did these particular plants evolve? How do they fit into the long history of life on Earth? How did they come to have so many shapes, colors, and sizes, and spread to so many different continents and climates? Iris is a wonderfully diverse genus, with between 200 and 300 species. And it is part of a larger iris family (which botanists call Iridaceae) that includes something like 2000 species, including other familiar garden plants like the crocus and gladiolus. Early botanists tried to deduce the family trees and family history of plants by noting their physical similarities and what clues could be gleaned from fossils. In this century, much has been learned from DNA studies, giving us a more complete picture of plant evolution. Peter Goldblatt of the Missouri Botanical Garden has taken a special interest in the Iris family, and Carol Wilson of Rancho Santa Ana Botanical Garden has studied the genus Iris itself in more detail. I’ve relied heavily on their work in putting together this post.

Origin of the Iris Family. Like many families of flowering plants, the iris family has its beginnings in the late Cretaceous period. At that time, the Earth’s climate was about 8C (15F) warmer than today, and there were no polar ice caps. Sea levels were high, and many areas were covered by shallow inland seas. It was a time when flowering plants were spreading throughout the world. They were diversifying and evolving rapidly, both encouraging and encouraged by the simultaneous evolution of bees and other insect pollinators. The iris family probably got its start about 82 million years ago, in what is now Antarctica.

Antarctica?

At that time, Antarctica wasn’t centered on the South Pole, but was nearer Africa, with some parts of it extending well north of the Antarctic Circle. It was still joined to Australia on the east. The climate was temperate, although cool, and the high latitude made for long summer days and long winter nights. It is thought that the strappy, vertical leaves (a distinguishing feature of the iris family) evolved to make maximum use of the sunlight, which would have been nearly horizontal much of the time. Two of the earliest branches of the iris family were isolated in Australia as it broke off from Antarctica, and five others developed in Madagascar and South Africa. (Madagascar and India were wedged between Antarctica and Africa in the southwest Indian Ocean at the time, making it possible for plants to migrate between the two continents.)

Around the time these different branches of the iris family were evolving away from one another and beginning to develop their own separate identities, the Earth experienced one of its great mass extinctions when a meteorite struck the Earth in what is now the Gulf of Mexico, 66 million years ago. Most people think of this event in connection with the extinction of the dinosaurs, but its effects were much more far-reaching than that. Many species of plants that depended on photosynthesis were driven to extinction by the dark envelope of dust that shrouded the Earth following the impact. 

Fortunately for the iris family, Antarctica, Australia, and South Africa—on the opposite side of the globe—were the best place to be. Although it is estimated that more than half of North America’s land plant species were lost in the extinction, few if any species were lost “down under,” although the numbers of individual plants plummeted.

With Antarctica moving south and the world growing colder, the future of the iris family now belonged to these plants that had colonized Africa and other warmer lands.

Two of the types of early irids (members of the iris family) in south Africa turned out to be very successful, spreading to other parts of the globe. These are also the branches of the family most familiar to gardeners today: iridoids and crocoids.

Iridoids and Crocoids. No, they are not rival alien factions from Dr. Who. The iridoids are members of the iris family related to irises, and the crocoids are members of the iris family related to crocuses. The iridoids include irises, as well as other familiar genera like Tigridia, Sisyrinchium, Moraea, and Dietes. A prominent distinguishing feature of the iridoids is their wide, arching, petal-like styles that cover the anthers and end in a crest. We can picture this emerging as an especially effective way to channel bees into the heart of the flower. The crocoids include crocuses of course, but also Romulea, Ixia, Tritonia, Freesia, Crocosmia, and Gladiolus. It’s hard to imagine a stylish modern garden without at least of few of this crew. Crocus, Romulea, and Gladiolus eventually found their way north into Eurasia from their south African origins, but it was the iridoids that eventually made it all the way to the Americas.

Iris. In the iridoid clan, the closest relatives to the irises themselves are the South African Moraea, Dietes, and related genera. Iris separated from these genera about 45 million years ago. The great sea that had divided Africa from Asia was gradually narrowing and vanishing, perhaps allowing the ancestors of the irises to find a new home in Eurasia. Later, the Sahara and Arabian deserts would prevent their return south.

Turkey seems to be the center from which the genus Iris has spread throughout the northern hemisphere. Many different types of irises are found in Turkey today, whereas most other regions have just a few local species.

For centuries, botanists had assumed that the most fundamental divisions of the genus could be seen in the different rootstocks: Junos with their bulbs and fleshy roots, xiphiums (which include the Dutch irises so popular with florists) with their tulip-like bulbs, the small reticulatas with their bulbs covered in netting, and of course those that grow from rhizomes. Some botanists even put these groups into different genera based on their rootstock. The rhizomatous branch of the genus was presumed to have then split into beardless, crested, and bearded sorts.

Iris unguicularis 'Lavender Moonbeams' (Tasco, 2014):
the newest version of the oldest iris?
photo: Superstition Iris Gardens

What has become clear recently is that these different rootstocks do not represent an early division of the genus into separate branches. Early irises were probably all beardless and all grew from rhizomes. These evolved into several different branches still having these basic characteristics, and then some of these branches gave rise to offshoots with deciduous foliage and bulbs as an adaptation to climates with very dry summers. So spuria irises are more closely related to Dutch irises than they are to Siberians, for example. Crested irises arose in more than one branch of the family tree, and are not a precursor to the development of beards. The earliest group to branch off from the others is represented today by Iris unguicularis and the closely related Iris lazica. If you want to have a mental picture of what the ancestor of all irises was like, Iris unguicularis is a good candidate.

Next, the family tree split into two branches, one of which spread mostly westward in the vicinity of the Mediterranean, while the other spread mainly northward and then east into northeast Asia and eventually North America. The Mediterranean branch produced the bearded, oncocyclus, and Regelia irises, but also gave rise to the Junos, and apparently the crested irises of east Asia, such as Iris japonica  and Iris wattii. These are actually more closely related to the Junos (which also often sport crests of various sorts) than to any other groups. Interestingly, one small branch of this group gave rise to both Iris dichotoma and Iris domestica, once thought to be so dissimilar that they were each placed in their own genus!

Meanwhile, the Asian branch of the genus led to the spurias, xiphiums, and reticulatas, plus most other beardless species. The migration of irises into North America was apparently not a single event, as there is no single branch of the iris family tree that has all the American irises and no Asian iris. The American crested irises, including Iris cristata, have the oldest lineage, but they do not seem closely related to the east Asian crested irises, as was once supposed. The crest feature developed independently in these two distantly related branches. A second venerable branch of irises in north America includes Iris missouriensis (the Rocky Mountain Iris), and the western species Iris tenuis. The Louisiana irises represent another early branch of the evolutionary tree. The other North American irises were presumably later arrivals, with close cousins in Asia. Iris virginica is related to the Siberian Irises and to Iris pseudacorus; this Asian-American grouping has a common ancestor with both the Pacific Coast group and also with the widespread Asian Iris lactea.  

Bearded Irises. The bearded irises grow around the Mediterranean, with some species ranging northward into central Europe. The tall bearded irises were the first to attract the attention of European nurserymen and plant breeders in recent centuries, and they are the most represented in our gardens today. There was probably an earlier division of bearded irises into dwarf species with a basic chromosome count of 8 (Iris attica, Iris pseudopumila, and Iris pumila, which apparently arose as a tetraploid hybrid of the first two) and other species (mostly taller and branched) with a basic chromosome count of 12. It is from this latter branch that our modern TBs, BBs, and MTBs are directly derived. The chart of bearded iris relationships here is not from DNA studies, but based on chromosome analyses, geographical considerations, and other suppositions.

In the big picture over long time scales, we think of evolution as a branching tree, where populations divide, become isolated, and go their separate ways to form new species. But if we look at the process in more detail, we see that species sometimes come about in other ways: as hybrids of earlier species, by polyploidy (doubling or otherwise increasing the number of chromosome sets), or by both these processes at once. The relationships among the bearded irises, for example, sometimes resemble a branching tree, but in some instances are more like a network, which species separating and then coming back together to make new species. Evolution is an intricate process.

Irises, being prized as garden flowers, have attracted the attention of human breeders. When looking at the difference between modern hybrid TBs and their wild predecessors, it is tempting to see a new, accelerated evolution now dominated by human intervention. But although the effects of human breeding efforts are dramatic, it remains to be seen what impact they will have in the long term. Our own genus Homo is perhaps 3 million years old; the genus Iris has been here about fifteen times as long already. The last two centuries of iris breeding, compared with the 45-million-year evolution of the genus, is a very tiny fraction indeed (the same as about half a second out of a day). The irises humans have created mostly depend on humans for their existence—you find them in gardens, and sometimes in old cemeteries, but they have yet to take over the Asian Steppes or the Amazon. Will there still be irises 5 million years from now? 20 million years from now? Will our present interest in them leave any traces that far in the future? 

Plate tectonic maps by C. R. Scotese, PALEOMAP Project (www.scotese.com). Used with permission.

Species Irises: Back to Nature

by Tom Waters

Iris missouriensis, a beardless species native to North America

Iris missouriensis, a beardless species native to North America

Iris missouriensis, a beardless species native to North America

I became interested in irises as teenager. After a year or so of growing tall bearded irises, I became more aware of the other types available, and of the special groups of enthusiasts who had gathered around each type. When I discovered that there was a group (SIGNA) just for “species iris”, I was baffled. In my biology classes at school, I had learned that the species was the basic category for classifying all life on earth. So didn’t all irises belong to some species or other? It didn’t make sense that there would be a special iris society just for species.

Beginning classes in school, naturally, emphasize simplified basic concepts at the expense of all the qualifications, complications, and exceptions that the real world has to offer. In school I learned that two individual animals or plants belong to the same species if they can breed and produce fertile offspring. But that’s not always the case, especially in the plant kingdom. Irises belonging to two different species can often cross and produce fertile offspring, and in fact this is how most of our named garden varieties of iris originated. Those named varieties (“cultivar” is the precise term) are almost all hybrids, with two (or more, usually) different species in their ancestry.

So now it started to make sense. People interested in “species irises” were interested in the original iris species that exist in nature, as opposed to the many garden cultivars that had been produced by hybridizing, crossing different species with one another.

Iris paradoxa, an aril species from northeastern Turkey

Iris paradoxa, an aril species from northeastern Turkey

I grow bearded and aril iris species, because I’m interested in hybridizing with them, and also because they come from parts of the world with climate similar to my own, so it seems a good fit. Many people grow other kinds of species: Siberians, Louisianas, and wild irises from North America, Europe, and Asia.

Iris reichenbachii, a bearded species native to the Balkans

Iris reichenbachii, a bearded species native to the Balkans

Iris reichenbachii, a bearded species native to the Balkans

What is the appeal of species irises for gardeners? Obviously, botanists are scientifically interested in the original species, which are the product of natural evolution and occupy distinct ecological niches. For a gardener or iris hobbyist, this scientific curiosity can inspire interest in the wild species. But there are other lures as well. There are many species that have been used infrequently or not at all in hybridizing. If you take a fancy to these, you will necessarily be growing species. Some of us like the “wild look” as an alternative to the deliberately “altered” creations of human hybridizers. And some like the idea of growing the wild irises native to their own area.  For others, conversely, species from other parts of the world provide a connection with the plant life of distant lands and environments.

Iris stolonifera, an aril species from central Asia

Iris stolonifera, an aril species from central Asia

Iris stolonifera, an aril species from central Asia

If you take an interest in species irises, you soon learn an important difference between species and hybrid cultivars. The hybrid cultivars are all propagated by division. Each plant is an identical replica of the original. Each one is really an individual organism, as distinct from all other irises as you or I are from all other people. But a species is not an individual. A species is an entire population of related individuals; it is like the whole of Homo sapiens from all the places humans live, with all their different characteristics and genetic heritage. So whereas I can “have” a particular cultivar, say ‘Dividing Line’, in my garden, I cannot “have” a species, such as Iris pumila. I can only have at most a few individual plants that belong to that species. They will all be different individuals, and all different from the great numbers of other  Iris pumila plants growing wild in Eastern Europe.

Species enthusiasts embrace this fact, and often strive to have a range of different plants representing each of the species they grow. This not only adds interest to the collection, but helps preserve some of the genetic diversity of the species in our gardens. Like many wild plants, irises are often threatened in their native environment by human activity and encroachment. The gardener who grows species contributes, in a small but potentially significant way, to their conservation and preservation.

For those of us interested in hybridizing, growing many different plants of the same species offers another benefit: genetic diversity.  If you trace the ancestry of our garden hybrids back far enough, you will find the same ancestors appearing over and over again. Despite all the range of color and form in the modern hybrids, they actually come from a rather inbred gene pool. Going back to the species expands the genetic base for our hybridizing efforts.

Iris pumila, a bearded species from eastern Europe

Iris pumila, a bearded species from eastern Europe

Iris pumila, a bearded species from eastern Europe

This brings me to a final observation. One can obtain species plants from commercial sources and others who grow them, including named cultivars in some cases (these are selected individuals of the species, not hybrids between different species). But it can be even more satisfying to raise species from seed. Many iris societies and rock garden societies have seed exchanges, where one can inexpensively obtain seed of many different iris species, including sometimes seed collected in the wild. There are also some commercial sources, mostly specialist plant collectors. When you raise irises from seed, you will naturally be “selecting” those plants with the genetic predisposition to do well in your own climate.

Growing species irises, particularly growing them from seed, provides a window onto the natural world that growing only hybrid cultivars cannot. There is a special pleasure that comes from raising these lovely wildflowers, knowing that you are enjoying (and helping preserve) some of the world’s beautiful and fascinating flora.

Iris missouriensis growing wild near my home in northern New Mexico

Iris anguifuga - The missing link?

by Jim Murrain

     Iris anguifuga is native to China and has been cultivated for centuries around summer gardens to repel snakes from entering the grounds and, when the rhizome is ground into a paste, applied topically as an herbal remedy against snakebites (or so these ‘Old Wives' tales go). This clone was collected by Dr. James Waddick in 1989 and has been named 'Snake Bane'.

     'Snake Bane' is a typical beardless Iris in many respects. It has that generic shape and color of many irises. It could easily be mistaken for a Spuria Iris at bloom time. However, it has a marked difference from all other irises, it is dormant and leafless during most of the growing season. Iris anguifuga begins growth in late fall as other irises are getting ready for winter and the snakes are going into hiding. It remains green in my z6a garden all winter although at only two to three inches in height. In early spring it puts forth a burst of growth and is in flower by mid-May. Around June, as the snakes emerge and gain their strength back, the Iris goes dormant or 'disappears'.

     These two older photos give a better idea of the true color. I. anguifuga is vigorous in full sun and makes a nice clump quickly. It will grow in partial shade but flowering will be reduced.

     The missing link? Iris anguifuga spends summer as a compact bulb. When it breaks dormancy in the fall it grows a rhizome. After flowering the rhizome withers away except for the growth point which pulls together in the form of a bulb. It is thought that this may be how bulbous irises first developed. 

     This illustration from the book Iris of China shows Iris anguifuga on the right half, 1 through 5. You can see the bulb shape has formed just before the rhizome will disappear for the summer.

     It is a modest plant in the garden with a simple display, but the story is a real conversation starter and who knows?  Maybe it will keep the snakes away, too.