In 2000 as I prepared to row out my tetraploid Louisiana iris seedlings noticed that one of the tetraploid seedlings looked unhealthy or slightly chlorotic. Closer inspection showed that most of the larger leaves had streaks of yellow and cream. This tet seedling was planted along with its siblings in hopes that whatever was ailing it would be remedied with the fertilizer that was previously worked into the new seedling bed.
The tet seedlings hit the ground running. The troubled tetraploid continued with the streaks of yellow and cream which became more pronounced as the leaves matured. I finally decided to consider it a variegated tetraploid Louisiana iris. The degree of variegation in the leaves was very erratic with some of the leaves showing a nice margin up the entire leaf while others just had a blending. I knew from experience that this type of variegation was highly unstable and that the plant usually outgrew the mutation.
This type of mutation occurs when some of the chloroplasts in the plant cells lose the ability to produce the green pigment chlorophyll. These plant cells with mutated chloroplasts divide producing a patch of yellow or cream on the leaves. The chloroplasts are positioned within the plant cell but are located outside of the nucleus. Essentially this means that the plant can't genetically pass this mutated trait on to it's offspring by breeding or back- crossing. So, the best we can hope for is that the mutated chloroplasts keep dividing and hopefully gain a little ground against the normal chloroplasts in the plant cells giving us larger streaks or margins of yellow or cream. There are varying degrees of this variegation due to the number of mutated chloroplasts within each cell. Yellow coloring means that there are several mutated chloroplasts within the cells and as the number of mutated chloroplasts increases in comparison to the normal chloroplasts the coloring gets lighter-such as cream and finally white. Well, enough with the botany lesson- let's get to the good part!
Spring finally arrived and the tet seedlings began to put up bloom stalks. The variegated tet barely showed any signs of variegation on the foliage so I resigned myself to hope for just a pretty bloom. Much to my amazement the bloom stalks were nicely variegated with one of them having nearly completely white sheath leaves. Another offset had a streaked bloom stalk which contrasted nicely with the red blooms. As the blooms faded and the seed pods began to swell, I noticed that they were also variegated.
It is now 2004 and the variegated tet still performs much as it did the first year-with no more but no less variegation. Unfortunately, the amount of variegation within this tet Louisiana iris isn't enough to compare it to the variegated tall bearded iris nor will it be a focal point in the garden. I am currently experimenting with other means to force them into producing more mutated chloroplasts. Keep your fingers crossed, and I will keep everyone posted.
*William Bruner is a resident of Owensboro, KY. He is the great nephew of the late Samuel N. Norris, who was also a pioneer with tetraploid Louisiana Irises. He has made good use of tetraploid irises bred by Norris and the late Joe Mertzweiller of Louisiana in his hybridizing program.
This article was originally published in the SLI Newsletter in the Spring 2005 edition.