Notes For Reference:-

Species, Varieties, or Forms in the Genus Nuphar:

Nuphar japonicum / Kouhone
　

Nuphar japonicum / Kouhone コウホネ

Nuphar japonicum is a perennial herb that inhabits shallow ponds or swamps; its underwater leaves are long, narrow, and membranous. The ones above the water are in the long, oblong shape, 20-30cm long. Long flower stalks emerged from rhizomes, bearing single, bowl-like, 4- 5 cm in diameter flowers on their tops; petal-like sepals are 5 in number, yellow, which turn green after flowering. The petals are in the shape of an oblong, half the height of the sepals, bending outwards. Bloom time: June-September.