Caltha palustris is a little-known native bog plant known as marsh marigold. A denizen of regions with minimal summer heat (Maine west into the Dakotas, and south down the spine of the Appalachian mountains), marsh marigold grows where you would expect to find it...in a marsh. Marsh marigold can spread to make a large patch, but sadly, much of what is sold as caltha palustris is actually it's evil cousin, the highly invasive Ranunculus ficaria, so be very wary.