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