I just came across this list of plants that are listed with their attributes with regard to nectar and pollen. I've noticed that goldenrod, alfalfa, mint, dandelion, and clover are some of the most mentioned plants in articles on which flowering plants honey bees love. I think it would be a safe bet to say that if those were planted around your beehives the bees would be more than happy. All of those plant seeds are easily obtainable and, depending on your location, grow wildly. In my area dandelion and clover are almost considered weeds they grow so abundantly. The leaves of the latter are actually used by my grandmother to make Italian style salads.
Next spring/summer I can get as many dandelion seeds as I want and anyone is welcome to have some, gratis. Mint also grows in one part of my yard prolifically and its cuttings are easily rooted with no hormones whatsoever. If anyone wants some feel free to message me.
Attached is a pdf of plants which produce flowers that honeybees love. Enjoy!