Potato flowers need to be buzzed to get the pollen out, and that works only with a few varieties (many are sterile). Like tomatoes. The anthers have tiny pores and the pollen comes out only when the flower is vibrated. No nectar, and honeybees can't do the vibration trick whereas bumble bees can (and do).
Beans? Great sources of pollen and nectar. The flowers are a bit tough for honeybees but they can open them. They find them easier after a bumble bee has already visited. Also, some bumble bees bite holes in the back of the flower and honeybees can rob nectar through the holes. Beans also have nectaries on the stipules, leafy scales on the stem. Bees will take nectar from them too.
Gavin