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

9 Out Of 10 Gardeners Recommend Crests

by Jim Murrain

The best known of the Crested Iris is Iris tectorum. It is often referred to as the 'Japanese Roof Iris'. Of course we now know that it is not native to Japan nor does it grow on roofs unless forced to do so. It is one of the most common of the irises native to China. 

 It is very easily grown from seed or, thanks to its fairly large rhizomes, from divisions. Iris tectorum seeds have been available via the SIGNA (Species Iris Group of North America) Seed Exchange every year since I joined almost 25 years ago. It remains a very popular iris.

When grown from seed and a goodly number planted in your garden you can admire the many different shades of lavender and even white this iris manifests.

However we must take note of the crests! They can vary a lot on each seedling and somewhat on each fall! It can look almost like a simple beard or large jagged ridge to wild shapes that remind me of corals seen  under water. 

The amount of spotting or water marks on Iris tectorum can also be highly variable. It can have clear clean colors to heavily marked petals. The marks show predominantly on the falls but can manifest on the standards also. 

This is one Iris where you can say "I have the blue, now I want the white". But the fun of growing a number from seed is to see the natural variations that can occur.

Even after being grown world wide for many years there are only a few named selections available, and they were primarily chosen for larger flowers or the amount of spotting. None of the odd forms have been chosen. I'm sure some of you would enjoy a monstrous form as seen here:

Iris tectorum has a huge range in its native land and can be grown in most places where people live. It will need a protected location in very cold climes and may benefit from growing in a pot under shade in warmer areas to help keep it cool when dormant. It is a fun iris in so many ways, and so easy even a child can grow it.

Most of the photos were taken in the garden of Rick Davis of Independence, Missouri and grown from SIGNA seed.

Those Puzzling Iris Names

By Griff Crump

Some time ago  --  a few years, actually  --  the question arose on iris@hort.net as to why the various species of iris are named as they are. A whole list of puzzlers had been submitted. 

I. tectorum

While most irisarians have heard that I.tectorum means “iris of roofs” or “roof iris”, stemming from the Japanese practice of growing them on their roofs (although I have seen that explanation disputed), the meanings of other names remained obscure. Being the compulsively helpful person that I am, I offered the following explanations for some of them, which I repeat here for those who are not iris@hort.net veterans:

attica -- similar to tectorum, but grows beneath the roof

subbiflora -- same as attica, but two floors down

mandschurica -- a variety, candidans mandschurica, will sit quietly in your

garden for years, then suddenly burst into bloom

acutiloba -- smelling this one can give you a very bad case of iloba

barnumae -- a real circus of color

bismarkiana  --  though plantings may be dispersed, this one will

consolidate and take over your garden

gatesii --  to be planted at the entrance to your garden, of course

hookeriana  --  (ahem, well . . .)

wattii -- in sufficient quantity, this becomes known as voltii

minutoaurea  -- a little bull goes a long way

odaesanensis -- comes from Odessa, but ran into a spelling problem

bulleyana -- crowds out other flowers

innominata -- Linnaeus lost the tag; very common; most of us have some

nelsonii  -- British; has only one branch

crocea -- Kasparek reject, who, looking at it, said "That's a croc."

ludwigii -- first cousin to hartwegii

foetidissima -- a real stinker

bungei -- you can't get rid of this one; it just keeps coming back

farreri -- Italian, misspelled

lazica  --  has to be staked

aitchisonii -- named after the well-known railroad town  (Aitchison, Topeka

and the Sa-anta Fe)

hartwegii -- first cousin to ludwigii

galactica -- honoring the Battlestar of the same name

stenophylla -- a nice present for your secretary

stocksii -- you buy this one when bondsii is too pricey

zaprjagajewii -- named for its discoverer, a Cossack who fell into a clump

of it when his horse missed a steppe

No doubt others among us have explanations for some of the rest.  


You can see the names of all the species irises and many beautiful photos of them at the Species Iris Group of North America (SIGNA) website.


Editor's Note:  Griff invites you to add your own "definitions" for iris species names in the comments section.  Be sure to keep it clean and, above all, funny!