The Genus Hosta
W. George Schmid (1991), says that this is called the
"dark-flowered hosta" in
Japan where it grows in moist woodlands and forest margins." The
flowers in this taxon have the darkest coloration in the genus
with very dark purple lobes with even darker stripes."
according to Schmid.
The Hostapedia by
Mark Zilis (2009), this plant which is "...native to Hokkaido Island,
Japan" is extremely rare. He says it is a "small size mound of green
foliage topped by deep purple flowers."
This hosta grows to an upright, medium size (12 inches high by
10 inches wide) plant with dark green foliage. It bears dark
purple flowers with darker stripes and yellow anthers in July.
Mikiko Lockwood in an article on The Hosta Library titled,
A Little About Japanese Hosta Terms defines the term kurobana or kuro bana as dark-colored flower.