Caltha palustris.

Botanical name: 

Caltha palustris Linn. Ranunculaceae. Cowslip. Marsh Marigold. Meadow Bright.

Of northern climates. This well-known plant, says Gray, is used as a potherb in spring when coming into flower, under the name of cowslip. In the Southern States, the flower-buds are pickled for use as a substitute for capers.

Sturtevant's Edible Plants of the World, 1919, was edited by U. P. Hedrick.