Doubles are well known for this phenomena. Cheerfulness is one that is supposed to be immune to it, as your experience is showing. I think I'd send them to the back for awhile.

RM, my "Stuttgart" turned out to be a plain leaved green variety! I got it from ebay. Is that where yours came from too? There were two in the package and one of them was rotten when i got it and never came up. Nancy

I have two 2-year old John Warren clematis side by side about 3 feet apart. The foliage looks fine, but the flower buds are acting weird. They appear and seem to slowly get bigger, but then they just don't open. In fact, one of the buds was opening nicely this past week (albeit the flower looked kind of small), then a couple of days ago, I noticed that the half opened flower just started to get brown around the petal edges. It's been warm and dry, but I have it in dappled shade with some sun throughout the day, plus I've been watering it regularly. I just don't get it...the foliage is all nice a green, yet the buds don't seem to materialize to anything. Does anyone have any theories about this? I sprinkle Osmocote granular fertilizer around all 21 of my clematis, and none of them behave like this. Thanks for helping me solve this puzzle.

Terrin, I sure wish I could help... I'm having the same problem and no one seems to have a clue. At least I know I'm not alone. It's really weird because the foliage is just fine and for me it's not even all of the flowers... just some of them. I've taken some of the affected flowers to my local county extension office and even talked to Maurice Horn (one of the owners of Joy Creek Nursery) to no avail. Fortunately it's not all of the flowers. Perhaps someday we'll find out...