i take it they're outdoors?
what you're seeing is more a sign of sexual maturity and not really a sign that they're flowering.. if they're outdoors, not much you can do buy roll with nature..
as we start to get further along into august, the days will start to get shorter and the dark hours longer, forcing the flowering hormones to build to a point that forces the plant to start to grow buds. it shouldn't be very long now, even though i'm not really an outdoor person, common sense tells me that summer solstice was june 20th i think this year, which is the longest day of the year, and every day there after we start to lose day light slowly each day.. once the days get short enough, your plants will flower.