Purchase bagged, long-fiber sphagnum peat moss; do not use baled peat moss that is commonly sold as a soil amendment. Soak the moss in water until it’s soft and fully hydrated, about an hour.
Choose a healthy staghorn fern with erect green fronds and an intact basal frond, or round “collar." Remove your fern from its container, if it’s potted, and gently dislodge all soil or peat from its roots. Take care not to tear the roots. Rinse roots thoroughly.
Spread roots in a radial shape. Take a handful of peat moss and squeeze out excess water. Gently pack the moist moss onto the back of your staghorn fern, in the “cup” that is created by the rounded basal frond. Press the moss through the roots to fill the round frond, and pack the moss on top of the roots to cover them.
Choose a mounting site on the fence that is in a shady spot; direct sun will burn the fern’s fronds. Find a spot high enough that is out of reach of dogs, rabbits and other small animals.
Enlist the help of a friend to make mounting an easier job. Hold the staghorn fern against a wooden fence post or an upright fence section. Using nylon pantyhose, twine or strapping tape, attach the fern to the fence in a tic-tac-toe pattern, leaving the center of the pattern open for your fern. Secure all free ends of the pantyhose, twine or tape with a staple gun.