The Marsh marigold or Kingcup, Caltha palustris, is a British native, producing large buttercup flowers in spring. It is ideal for a bog garden or he edge of a pool. There are related species from elsewhere, some with yellow and some with white flowers.

Caltha palustris is the, dare we say, bog standard form. Large yellow flowers and healthy clumps of foliage, growing by preference in marshy places and even shallow water.