Monday, September 19, 2016

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?

1 comment:

  1. Excellent article. Very informative.

    Ron Thoman