Wikipedia
Hylomecon
Hylomecon vernalis, also known as the forest poppy, is a poppy of the Far East, ranging from Manchuria to Japan.
This poppy is a perennial that spreads via rhizomes, typically no taller than 30 cm. The pinnate leaves usually have five soft green leaflets, although three and seven occur as well, each with a shape ranging from lanceolate-oblong to rhombic, and a pattern of distinct teeth along the margins. The flowers are bright yellow 3.5-5 cm across, starting out bowl-shaped, then flattening out with age.
Its typical habitat is moist shaded woodland, growing in accumulated humus.
Although generally considered a monotypic genus, the species is somewhat variable, and several variations have been named as separate species.