Dahlias opening up in center in late fall, why?
Most of my dahlias have survived the first couple frosts with only minor damage but now it seems like many varieties are opening up in the center that were fully double a month ago. In general it seems that dahlias prefer somewhat cooler weather so I thought they would continue nicely after the first frosts. What do you think is causing this now? Shortening day length perhaps? Or maybe just general end of season stress? On a positive note, my Maarn dahlias are still putting out lots of nice fully double ball form blossoms. :) Victoria Ann is still producing nice flowers too.
Looking in Specialty Cut Flowers by Allan Armitage I see that day lengths below 11 hours have been shown to have a deleterious effect on blossoming of dahlias. My day lengths are now a bit below the 11 hour mark so maybe this is part of the cause of my defective flowers.