Kingcup, or Marsh Marigold, is a short- to medium-sized perennial of the buttercup family. The flowers consist of five bright yellow sepals.
The leaves grow on long stalks and are thick, scallop-edged and kidney-shaped.
It grows in marshes, fens, lakesides and even in open fields in wet clay soils; it is larger and more luxuriant in the shade. The plant is common all over Ireland. There is a double-flowered variety 'Plena' used for water gardens.
The flowers are open from March until June.
Kingcup grows in Britain, in temperate and Arctic Europe, temperate and Arctic Asia and North America.