This grower is fairly sure of this plant identification.
Marsh marigold, Water cowslip, Kingcup, Water blobs, Moly blobs
Caltha palustris (Marsh marigold). This is one of the most rewarding bog plants that can be grown in the garden. In the spring it will produce a profusion of rich yellow blooms. It will also grow well in a rock garden that is kept moist or even a perennial border. The leaves are a dark green and provide a nice contrast for the bright flowers. 'Flore Pleno' will not grow as tall, but will provide double flowers. This plant is often found in the wild in Northern Europe.
The plants will require moist and well drained soil, and the larger species are best in marginal conditions. Most will prefer an open sunny position.
Aquatic, bog, wildflower/meadow