In my second season with my own bees and having tried to plant flowers attractive to the bees, I have noticed a couple of things:
First, bees don't tend to be very attracted to small numbers of flowers. There may be a bee or two here and there, but it is hard to gauge the quality of the flower unless you have sufficient number of them. The number of bees tend to coincide with the number of flowers. So one plant will generally not get a crazy number of bees. (I had a single chive, for instance - and it seemed like one single bee was there every day, and that would take all the plant had to offer). So if you want a lot of bees, you have to have a lot of desirable flowers.
The flower blooms in early spring or late fall. In these times, flowers are less common, and the bees will pay greater attention to the ones that are available.
For instance, I have a few crocuses around, but the bees definitely pay attention to each and every one. Last summer, I planted borage in the garden, and the honeybees paid little attention to it during most of the season, as there weren't that many of them. However, it's flowers lasted into November, and late in the year, the bees were all over it.
So if you want flowers to get the bee's attention, it's got to be early, late, or plentiful enough to make it worth their while during the main season.
This year, I'm trying some new flowers, and in each case, I plan to grow a good number in order to get a more accurate read of the attractiveness to the bees. If there are too few, more available plants will get their focus.
Those are some of my perspectives, have yours been similar?