https://www.minnesotaseasons.com/Plants/yellow_marsh_marigold.html
Yellow Marsh Marigold (Caltha palustris var. palustris) — Minnesota Seasons
Yellow marsh marigold is a native wetland perennial, distinct for glossy heart-shaped leaves, hollow fleshy stems, and bright yellow buttercup-like blooms.
yellow marsh marigoldcaltha palustrisvarminnesotaseasons