Here in central Wisconsin it is now prime time for this year's honey flow. Although the black locust flowering is complete many other large volume nectar sources are starting. In my walks around the neighborhood I have seen the following plants are now either in bloom or just beginning to bloom.
White and yellow sweet clover
Please note that the florets of the red clover blossom are too long and prevent most bees from reaching the nectar with their tongues.
It is a good practice to check the status of your supers on a weekly basis. A strong hive can easily fill a super in a week if nectar is available. Of course there will be a big variation between hives. Last week I was pleasantly surprised to find I have two hives that already filled the two supers initially installed on the hives. I happily added a third super to each. Conversely, other hives have yet to deposit any honey in the 1st super. My records, kept over several years, show most hives will have restocked the outer brood chamber frames and started storing honey in their supers by June 15th. You should have installed your honey supers by now; even on hives started with new packages this spring. Inadequate space to store the honey flow can also trigger swarming if the bees start storing honey in the brood chamber proper thus restricting the space in which the queen can lay. Proper hive management helps yield more honey.