This is a non-registered form of H. montana from Japan. It forms a large size hosta with green foliage that has a thick, white bloom on the bottom side.

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term urajiro as white-backed or white underside and the term oba or ooba as large leaf, 'Oba Gibōshi' or H. montana.