I remember exactly where I was when my Dahlia 'Yellow Hammer' first flowered...we tend to do that with really important events. Yes, I was standing in my garden looking at my Dahlia 'Yellow Hammer'. It was indeed a memorable sight, the dark black of the night, I mean...of the foliage and the stunning single flower, opening a butterscotch-yellow (RHS 163A)...did someone mention scotch? Sorry, butterscotch-yellow with orange streaks...that might be the scotch and not the flower. For us, Dahlia 'Yellow Hammer' flowers from early summer until fall, taking time to rest only in the hottest of weather.