I have some I don't want to kill, although some are appalled that I grow them. I bought three hybrids from Heronswood years ago and so far they have behaved themselves. One has a double yellow flower, another has a white flower, and the third, named 'Brazen Hussy', has bright yellow flowers but bronze, almost purple foliage. I can't imagine my garden iwthout a brazen hussy in it! I do keep my eyes on these three plantings, and they are in a perpetually damp spot, which they like, but they have not escaped from the bed yet. And for those who like to call ranunculus ficaria "marsh marigold", I also have the true native marsh marigold planted in this area for comparison. I often lecture in this corner of the garden! Bill Lee SW Ohio