Kingcup Caltha palustris

Caltha palustris commonly known as Kingcup or Marsh Marigold (also known as Calthus palustris syn. Trollius paluster Krause) is a member of the family Ranunculaceae, and is native to temperate regions of the Northern Hemisphere, growing in wet, boggy places. It is a herbaceous perennial plant growing to 80 cm tall. The leaves are rounded to kidney-shaped, 3-20 cm across, with a bluntly serrated margin and a thick, waxy texture. The flowers are yellow, 2-5 cm diameter, with 4-9 (mostly 5) petaloid sepals; they are borne in early spring to late summer. Stems are hollow. It is sometimes considered a weed in clayey garden soils, where every piece of its root will survive and spread. In warm free-draining soils, it simply dies away. from wikipedia, ( dutch name is Dotterbloem)