One of my pleasures is to observe bees working all the wildflowes in the area.Over the years I have never seen a bee on a buttercup(ranunculus)plant,when I did a search on this plant I learned that both its pollen and nectar are toxic,not only to bees but also livestock.The info did state that once the buttercup is cured(dried- as it is for hay)it loses toxicity. Again the foragers are making a good choice.