'Black Knight' Butterfly Bush

I have this Buddleia 'Black Night' growing outside the window of my home office. I planted it almost three years ago, shortly after we moved into this house. For the past couple of summers I've enjoyed watching dozens of butterflies sip its nectar. I've been worried this year because the bush has been in full bloom for several weeks and I have yet to see a single butterfly. But I guess I'm being impatient, I checked the dates on some of the butterfly photos that I shot last year and they were all taken in early September, so I guess it's still too early. At least I have something to look forward to in September.