My guess is that this is a temporary condition. Are the plants still very young?

George
Tahlequah, OK

No, they're not young at all. They were planted very early and suffered through an extended cold, wet spring time. They're several feet wide with huge leaves and more female blossoms that I can shake a stick at. It's just the two Sunbursts having this problem, the zuke right next to them has normal male flowers, although damn few.