like Jim says, it depends on the flower. I've have several varieties of bees & small wasps working my garden. right now the honeybees are on my cosmos, Russian sage, oregano, basil, bottle brush buckeyes, & moonflowers ( datura ). they're also working the clover in my yard pretty hard. around here the mainstay of the bees seems to be dutch white clover. when people ask me what they can do to help the bees i tell them to give up their grass only lawns, plant dutch white clover, & leave the dandelions be.