Buttercup a pink Oenothera? I wonder where that came from, since butter is yellow.
Ranunculus as sold under that name these days is a highly hybridized, ugly (to me) mess. I think (but don't hold me to it) that the fancy things were called "Persian Ranunculus" way back when.
Ranunculus the genus is huge, with hundreds of species, most quite plain.
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