I feel like everything is "just right" in your garden for Dahlias, kinda puzzling results, but I'm inclined to think sources have had something to do with it. I've had very hit and miss results from various local and mail order sources. It seems with Dahlias, what some folks think is great quality, others find very questionable. I had only been used to purchasing clumps of tubers, but the top Dahlia specialists send a tuber with at least 1 eye. Last spring I participated in a co op through Ednie flower bulbs and received clumps, of which each performed well and was true to name. Other participants were displeased with the clumps, preferring divisions, feeling they grow healthier plants.
Another possibility comes to my mind about varieties too. I know some varieties perform better in certain parts of the country than others. For example, The Georgia Dahlia society lists cultivars that perform in hot summers, which I understand can be challenging. We typically have hot summers, but Dahlias don't seem to mind. I wonder if there's a NY Dahlia society that may have similar lists? I'll check that out!
