While it’s fun to plan flowers for the bees, I find the bees like even better the flowers that come unplanned, unheralded, and unasked. Especially in spring, wildflowers fill in the gaps before the “official” flowers bloom.
If I had to pick a favorite wildflower, I think of fall and pick wild asters (with goldenrod a close second). The asters flower late, when the other flowers are faded, in waves of pastels ranging from pink and violet to white. They bring all sorts of bees, honeybees and bumbles, bees big and small, including my favorite little bee, the shiny green Agapostemon.
So here follows my list of wildflowers that attract lots of bees:
May: Virginia Sweetspire
May: Wild Rose
Late May-June: Bladder Campion
August to September: Goldenrod
September to frost: Wild Aster (Cultivated New England asters are good, too.)
In short, a little benign neglect in the yard will make a lot of bees and flower flies happy.