In Pursuit of Variegated Roof Iris

  by Bob Pries

Iris tectorum alba, Pries photo

Iris tectorum (the Japanese roof Iris) is one of the easiest species to grow. Many years ago, I heard about a variegated form and got very excited. In my eyes, the white flowers of Iris tectorum are one of the most enchanting of Iris flowers. Unfortunately, this variegated form was said to have blue flowers. I imagined how stunning the white flowers could be with beautiful variegated foliage.

When I finally saw some plants of this variegated form, I was somewhat disappointed in the quality of the variegation. It was much like some of the variegated, tall-bearded irises that have irregular streaks and stripes. It was, though, much more pronounced than what you see in virus-infected plants. However, the plants themselves were not robust growers, and this clone seems to have died out in cultivation.

There was one troubling fact. The insert image of the blue flowers was not Iris tectorum. At the time, I lived in zone 6 in Missouri. The image I thought looked very much like images I had seen of Iris japonica. But japonica does not tolerate zone 5 winters well. The foliage when received appeared more glossy.

Iris japonica flowers, Hensler photo

 

About the same time that I was eagerly searching for someone who could share a piece, I saw an advertisement in a general garden catalog. It showed an image of beautifully variegated foliage and a small insert of blue flowers. It proclaimed, "Variegated Iris tectorum for sale," so of course I ordered it. But the leaves were more slender than I. tectorum and it appeared I had gained a new house plant.

Variegated Iris japonica Pries photo

In trying to find out more about variegated Iris japonica, I found references that suggested there is more than one form of variegation and at least two types grow in Japan.

The next year I visited a very large perennial nursery outside of St. Louis. The proprietor—who I knew well—was proud to show me a huge planting of variegated Iris tectorum being used as a groundcover. It was absolutely gorgeous. I felt a bit guilty when I told him it was not Iris tectorum but japonica. I warned him it would not make it through the winter but he did not dig it up and it all perished. More and more I kept seeing Iris japonica incorrectly labeled as Iris tectorum in the trade.

Iris japonica, one of three focal points. The others are Brugmansia 'Snowdrift' upper right and variegated Curcuma; Pries photo

Since moving to North Carolina (zone 7) I have grown many forms of Iris japonica. Tony Avent’s Plant Delights Nursery (zone 8) has selected several with differing flower colors. All the green leaf forms survive my winters. They are especially good as groundcovers under the dry shade of Pine trees. But I still love the variegated form which I maintain as a pot plant. It seems just a bit more tender than its green cousin. It is especially attractive as a focal point in my houseplant garden and is a feature of my deck garden of potted plants. I would be delighted to find other forms of the japonica but someday I hope to grow a true variegated tectorum.

Variegated Iris japonica repeats the angular texture of Yucca 'Colorguard' Pries photo

The Beginnings of Tall Bearded Irises

by Bob Pries

My first blog! I thought I might start off with some thoughts about another beginning which occurred about 200 years ago. For years I wondered what the first tall-bearded irises actually looked like. Here is what I've found.

Circa 1820, E. Van Berg of Neuenkirche, Germany and Marie-Guillaume de Bure of Paris, France began naming cultivated varieties from the bee crosses appearing in their gardens. Van Berg did not introduce his selections into commerce. On the other hand, De Bure is noted for the first named and introduced cultivar ‘Buriensis’---which he named after himself. It was said to have a plicata pattern similar to the later ‘Madame Chereau’ but larger with more rosy markings outlining the white flower.

Although considered an “amateur” in 1848, De Bure was said to have the largest collection of irises in France. The book “The World of Irises” (available through the American Iris Society Storefront) credits De Bure for setting in motion the train of events which led to all present-day iris societies. It makes me wonder, "How many bearded irises did De Bure have in his collection?" By 1830, De Bure’s work had inspired fellow Parisian Henri-Antoine Jacques, the horticulturalist famed for introducing the Bourbon Roses. Perhaps his only surviving cultivar is ‘Aurea.’ Jacques in turn, inspired Nicolas Lémon of nearby Belleville, France (which was later annexed into the city of Paris).

Lémon was noted for growing thousands of seedlings. He did not bother with hand pollination and was quite happy with the work the bees produced. Nonetheless in 1840 he put irises on the map by offering 100 varieties for sale to the public.

 

This plate appears within Portefeuille des horticulteurs. Vol 2 (1848) with a nine page description

Between 1840-1850, Lémon continued to offer hundreds of irises for sale each year. To find descriptions of these irises we must go to the French literature. I am greatly thankful to Sylvain Ruaud and other members of the Société Française des Iris et plantes Bulbeuses for providing links to these descriptions of the Lémon varieties. Readers can find these by going to Lémon’s hybridizer page in the Iris Encyclopedia where you will find lists of his cultivars and linked references. The following plates show more of Lemon’s irises.

This plate appears within Bulletin du Cercle Général dHorticulture (1856)

American plant catalogs of this period rarely gave descriptions of these bearded hybrids and usually only offered collections of fifty or one hundred “germanica” irises. Although these bearded hybrids were often referred to as Iris germanica, it is likely that all of them had only Iris pallida and Iris variegata in their backgrounds. Experimental breeding between the two species by Sir Michael Foster, (of Trinity College in Cambridge, England) showed this to be the case. Since both species had chromosome numbers of 2n=24, their offspring were all fertile with each other also. Germanica irises grown in gardens at the time were probably ‘Grandmas’ Blue Flags’ a sterile triploid.

It was probably not until about 1885-1890 that fertile tetraploid Iris germanica was collected from Amasia, Turkey and Foster started entering true germanica irises into breeding. Lémon’s irises were all diploid, while Foster's ‘Amas’ was tetraploid. Thus, the early diploid irises really formed a fertile family distinct from today’s tetraploid tall bearded. The Lémon hybrids had more affinity to today’s diploid miniature tall bearded than to our modern tall bearded. The few that remain of the earlier group provide a delicate charm and grace to modern landscapes. I would love to see more images of them in the Iris Encyclopedia.