Another ssp. of Anemone narcissiflora, or Anemonastrum, depending what names you decide to follow.
This cold hardy species has the same beautiful large, white flowers, sometimes with a bluish back. The basal leaves resemble those of an Aconitum and are pubescent; short black-brown rhizome.
Germination: best sown as soon as possible; it may germinate in the second year after sowing.