Native celandine poppy (stylophorum diphyllum) is a lovely plant. I think the physical differences are what make it nicer than the alien celandine -- bigger, shinier flowers, somewhat darker foliage, more interesting leaf shape. In addition, however, the alien is really weedy. It seeds all over the place in my yard and is hard to control. Although I understand that the native will seed in as well, it certainly doesn't seem to spread widely, at least not where I have it.

I don't have the native celandine, but I do have the alien variety. In some locations in our area the alien seems to stay within reasonable bounds. However, in my location (wooded area only a mile or so away) it really takes off. It has reseeded so much that I'm almost ready to call it invasive. I'm constantly having to pull it out. Though it can grow fairly large (about the size of a medium bush and quite pretty) it doesn't have to be more than a couple of inches tall before it can and often does, flower and reseed. Not sure exactly which conditions allow this plant to behave so differently in it's growth habits other than the soil, since the lighting is the same and this plant isn't really too fussy. I am also at a bit higher elevation.

Do be careful handling this plant as the Yellow/orange sap can be VERY irritating to some people!!! This is considered a medicinal plant also.

Stylophorum diphyllum is quite aggressive in my garden. It is coming to dominate two large beds and has spread to my back woods where I am trying to keep it out. If I pulled out half of my plants I would still have too many. As for the alien I pull it our when I recognize it wherever it is.If you want a nice contrast in the seed pods (and foliage) try S. lanceolatum.