Well from doing a google search it flowers 'late' summer which I would view as later half of August, early September. Also if you only planted it in May it might not flower at all this year needs the time to establish itself.

having grown this myself, it doesn't flower usually till August, though its variable year on year, but i agree with MG above, it may not flower fully this year anyway. Remember to prune it back every year in spring as it matures.