Caltha palustris

Perennial of the Ranunculaceae family, widely spread across the temperate and boreal northern hemisphere, from Europe to Asia and North America. It is confined to wet environments: stream banks, ditches, marshy meadows, peat bogs, and shaded banks, from the plains up to altitudes exceeding 2,000 meters in mountain ranges.

It forms fleshy, spreading clumps, 20 to 50 cm in height, with hollow stems often lying at the base then upright. The leaves are kidney-shaped to heart-shaped, dark green and shiny, with finely crenate edges, and a distinctly leathery texture.

The flowers, borne in small terminal clusters, consist of five petaloid sepals of a bright, vivid yellow, almost waxy in the light. They are among the first to enliven wet areas with the return of spring.

In its natural habitat, its flowering extends from March to June depending on altitude and latitude. In cultivation, it blooms from March-April. The plant is toxic when fresh due to the presence of protoanemonin; it was once used with caution in folk medicine. It requires a constantly moist to waterlogged soil, in full sun or partial shade, and is perfectly suited to bank gardens and naturalized ponds.