Lesser Celandine

These flowers are an invasive species. The lesser celandine crowds out the marsh marigolds and other delicate native spring wildflowers that are trying to co-exist in the same environment. Lesser celandine is so bad that the US Geological Survey, not exactly an organization known for hyperbole, calls it a "travesty". Lesser celandine still seems to be a valued wildflower in England and Ireland, but in northern U.S. and southern Canada, it is an infestation.

Both lesser celandine and marsh marigold are low-growing with shiny green, rounded leaves, and big, shiny buttercup flowers. There are subtle differences in the appearance but the main way to tell them apart is by behavior. If you come across an entire yard, stream-side or forest thickly carpeted with the stuff, it is lesser celandine. Marsh marigolds grow in mannerly clumps; it doesn't take over.