Elkhorn Fern

Platycerium bifurcatum, the Elkhorn Fern, is an epiphyte that grows on trees and rock rather than in soil, and it carries two completely different kinds of frond: flat, rounded shield fronds that clasp the host and catch falling litter, and grey-green forked fertile fronds that hang down from them. Over years it builds a spreading clump of overlapping shields.
It is mounted on a board, a post or a host trunk, and it is one of the few plants that turns a blank shaded wall into a planted surface without a soil volume.
The Elkhorn Fern plants a shaded wall where there is no soil to plant into.