I have never seen it, but have kept my eyes opened for a Hulthemia seedling showing the blotch on the petal reverse. Is it possible?
Nearly always, the petal reverse on Hulthemias is lighter than the petal upper surface. Rarely, I have seen a darker reverse, but never a blotch on the reverse.
In the photo below, it appears that there is some of the blotch showing through. Is this sufficient evidence that a reverse blotch is possible? Probably not. Nevertheless, I will remain on the lookout. I think that a cut flower type rose would look extremely interesting with a reverse blotch on the outside part of the petals.
The petals in the next photo are from what is probably the best 'Double Knock Out' Hulthemia seedling that I have had so far. It appears extremely clean, sets hips well and germinates well. I am hoping to move this along in crosses to produce better cleanliness and better blotch conformation.