The Hulthemia Holy Grail - Blotch Heat Stability

When breeding for Hulthemia hybrids, it is the blotch that is the focus of one's attention.  Seedlings lacking blotches, or those having smaller or more faint blotches are quickly looked over when a bolder, larger blotch catches the eye.  Selecting for those seedlings only, that have the eye popping blotch, results in very few seedlings that remain after the initial culling process is complete.

It can be quite disappointing therefore when the blotches "disappear" on many of these select few seedlings.  Unfortunately, that happens quite frequently.

Both of the above seedlings had good to excellent blotches when they first bloomed earlier this year as new seedlings.  Notes on their markers indicate comments like "great blotch", or "wow".  As can be seen currently, however, there is nothing "wow" about either of these two seedlings (the same can be said for most of the other "select few").

I am convinced now that the condition that contributes most to blotch fading is the higher nighttime minimum temperatures present during the summer months.  Initially, I had thought that maybe it was the greater light intensity or hotter daytime temperatures that were the cause for the blotch "disappearance".  Over the last few years though I have noted that good blotches typically return in October.  That has been true even when the daytime temperatures in October have been over 100º F (unfortunately not a rare occurrence in Bakersfield).  In October, despite high daytime temperatures, nighttime temperatures usually drop into the mid-60's or lower.  It appears then, that sustained nighttime temperatures above 70º F have the greatest effect on blotch fade, and the higher the temperature the more important the impact.

'Eyeconic™ Lemonade', as seen below in a photo taken today, has some degree of fade, but it is not as pronounced as in the seedlings in the photos above.  'Eyeconic™ Lemonade' has been useful in producing other nice yellow Hulthemias, some of which seem to exhibit good heat stability.

The seedlings in the following photos are all exhibiting improved heat stability.  These will be used heavily in future breeding while I continue to search for the Hulthemia Holy Grail.

All of the photos in this post were taken on July 23, 2011, after having warm summer-type weather in Bakersfield, California.