i actually held a buttercup up to a bee on the entrance of the hive one time just to see if they liked it and a bee actually tried to sting the flower. so i figured they don't like buttercups. also as far as what leominster said about bees deciding what to get in the morning and staying with that bloom only, i'm guessing you mean individual bees because i always notice several differant types of pollen on my bees when i observe them, bright yellow/orange pollen from dandilions, light yellow from sorel, or greenish from blackberries among the many other colors i see.