Hylomecon

Hylomecon vernalis
A rhizomatous perennial, reaching up to 1.3 x 1.5 feet in size, that is native to coniferous forests in far eastern Russia, northeastern China, northern Korea and Japan.
The pinnate leaves, up to 6 x 6 inches in size, are composed of 7 to 11 toothed, ovate leaflets. The foliage is bright green.
The yellow flowers, up to 1.5 inches wide, are borne over a 3 week period during late spring.
Hardy zones 4 to 7 ( 3 on protected sites ) in partial to full shade on just about any moist, humus-rich, well drained soil.
Propagation is from seed or division.

Hylomecon japonicum
Nearly identical.