By Bob Hollingworth
Clear pink is a color we do not much associate with Siberians. There is white, blue, violet, lavender, red-violet, purple and now red/yellow blends, but not really a true pink. Pink is the poor relative as a color. Pink in irises can come from one of two sources, either from carotenoid (yellow, orange and pink) pigments or anthocyanins (blue, red, lavender and violet colors). Bearded irises have both types, and so clear pinks are not uncommon – think 'Beverly Sills' for instance. But, so far, there is no evidence for a carotenoid pink in Siberians (or other beardless irises to the best of my limited knowledge). So pink has to come through the anthocyanins, and of course this can give pinkish Siberians, but always with a bluish cast (lavender-pink, orchid-pink) – e.g. 'Pink Haze' (McGarvey, 1980) or 'Mary Louis Michie' (AM Miller, 1995). The fact that there has been little advance in achieving clearer pinks in Siberians in many years suggests that this is not necessarily an easy field to cultivate, but for that reason it is tempting as well as challenging.
Clear pink is a color we do not much associate with Siberians. There is white, blue, violet, lavender, red-violet, purple and now red/yellow blends, but not really a true pink. Pink is the poor relative as a color. Pink in irises can come from one of two sources, either from carotenoid (yellow, orange and pink) pigments or anthocyanins (blue, red, lavender and violet colors). Bearded irises have both types, and so clear pinks are not uncommon – think 'Beverly Sills' for instance. But, so far, there is no evidence for a carotenoid pink in Siberians (or other beardless irises to the best of my limited knowledge). So pink has to come through the anthocyanins, and of course this can give pinkish Siberians, but always with a bluish cast (lavender-pink, orchid-pink) – e.g. 'Pink Haze' (McGarvey, 1980) or 'Mary Louis Michie' (AM Miller, 1995). The fact that there has been little advance in achieving clearer pinks in Siberians in many years suggests that this is not necessarily an easy field to cultivate, but for that reason it is tempting as well as challenging.
As with so many other things, working in this
area came to my mind as an afterthought a few years ago when a batch of seedlings seemed to give
some marginal improvement in “pinkness”. These still tend to the blue side of
pink, but truly I think could be termed peppermint pink. One (09F3A3) is under
evaluation for introduction. Perhaps line breeding can slowly improve these
further, but I have a few other thoughts about where cleaner and
richer pinks might come from.
09F3A3 |
Just as external pH changes these colors, so does the pH
inside the cell (which is not directly affected by soil pH). Also, different metals and the interaction with other co-pigment
molecules can change color in a complex way that goes well beyond the bounds of
this blog. Subtle change in cell pH (as small as 0.1 unit) can cause a surprisingly
large change in the blue-pink color balance of flowers. Several tactics could work in theory to
take advantage of this to give purer pinks - increased cell acidity, greater
uptake of metals (aluminum) etc., but there is no obvious way to control these
as a hybridizer, so you can only make promising crosses and hope for a lucky
break in seedlings. Perhaps this is not just a pipe dream. There are quite
clear pink Japanese irises with similar pigments to those in the Siberians.
'Fancy This' |
I think this effect may be what lies behind two recent introductions from Jan Sacks and Marty Schafer, 'Fiona' (2010) and, particularly, 'Fancy This' (2012). To my eye these have a distinctly richer
pink color than previous Siberians. Even more exciting is the thought that if you can get purer pinks with less blue influence through mechanism 1 and then combine this with yellow in mechanism 2, you could head towards true orange. Dreams, dreams.
I believe they will get there. With your work, and the work of other fine hybridizers, there is little that won't be accomplished.
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