(aka: Dryopteris erythrosora var. koidzumiana) Dryopteris koidzumiana hails from lowland forests on Japan's Yakushima Island and was introduced into the US by fern expert Barbara Jo Hoshizaki in the early 1990s. For us, Dryopteris koidzumiana is effectively a much brighter version of Dryopteris erythrosora with new foliage that emerges brilliant russet red. Due to its warm origins, Dryopteris koidzumiana prefers warm summers and can be slow to re-awaken in cold summer climates like the Pacific Northwest. When happy in the woodland shade garden, you can expect an evergreen 2' tall x 2' wide specimen.