Adiantum x mairisii, Mairis’s hardy maidenhair fern, is a sterile hybrid between Adiantum capillus-veneris and an unknown presumed tropical maidenhair (A. raddianum or A. aethiopicum). Discovered ages ago in the British nursery of Mairis and Company and named before 1885 it rewards gardeners with typical hybrid vigor and surprising hardiness (better than either of its likely parents). Mairis’s maidenhair produces lacy, bright green 15 to 18 inch fronds supported by brittle blackish stipes (stems). While it is deciduous it holds its fronds well into the fall season. This exciting woodlander spreads about with welcome ease in light moist soil and filtered shade. In spite of its age it is relatively new to North American cultivation and is a rewarding addition for enthusiasts in Zones 7 to 10.