Viewing post #821109 by sooby

texaskitty111 said:Yes, same family.

Not a bean expert, but Aggie, Texas A & M, says "In the South and some other parts of this country lima beans are commonly called "butter beans."" U of Georgia Extension says "Lima beans are often referred to as butter beans, particularly in the South."

Their family would be Fabaceae. Their genus would be Phaseolus. I assume we're agreed that far? So the next stage would be to add the specific epithet, which is given in the references for both beans as lunatus. Even if both butter and lima are the same species, Phaseolus lunatus, they could still be further sub-divided into cultivars/varieties/undetermined rank. Thus they can both be Phaseolus lunatus but still be somewhat genetically different. For example the Wikipedia entry says "The term "butter bean" is widely used for a large, flat and yellow/white variety of lima bean (P. lunatus var. macrocarpus, or P. limensis[4])."

So, even if one goes with that latter distinction, it means that they are both still the same species, i.e. P. lunatus, but that butter beans would simply be a variety thereof. So, same species, same genus, same family, but possibly different variety or type.