An ancient fern, discovered by Richard Kayse in 1668, growing on a limestone cliff in South Wales. The plant is sterile, and so all plants in cultivation are divisions of the original plant.
This is a beautiful fern, which grows for me on very slightly acid, shaded soil under an apple tree. It dies down for a few weeks in mid-summer, and then sends up new fronds from mid-August, which remain fresh and green until the following late June. It needs well-drained soil.
I have categorised it as evergreen as it in leaf through the winter.