I agree, Ted, that it must be genetic. My 70 plants, some 20+ varieties, located in 5 different beds, are all blooming well with all the rain and mild temperatures here in Upstate NY. Except one plant: Mystique is growing well, currently has 5 nice blooms, all five are just now opening fully and have blown out yellow centers. I'll experiment with picking some a little too early, and see what that does. I'll also plant again next season to see if this trait carries forward. If it IS genetic, it ought to appear each season, correct? Disappointing, but overall an awesome growing season here.
In a related topic: since dahlia reproduction via tubers is asexual - 'Cloning' - and does not involve the mixing of genes that flower/seed reproduction does.....how is it that genetic traits appear/disappear in a particular variety? In other words, if all Mystique dahlias originate from one single original plant that was the offspring of a breeder crossing two other variries, then all of today's Mystiques ought to share the same genetic traits, including this tendancy to 'blast' open centers. True? Do Mystiques all tend toward open centers?