Damp, shaded wood surfaces outdoors are susceptible to lichens, which are flaky organisms consisting of algae and fungi. Lichen growth is prevalent on wood decks, porches and fences. Although beneficial to ecosystems, lichens cause wood decks and porches to become slippery and unsafe to access. Lichens also make outdoor wooden surfaces appear old and shabby. Fortunately, lichens don't damage or permanently discolour wood surfaces. Homeowners can kill lichens on wooden decks, porches and fences using nontoxic solutions.
Move all objects off the lichen-covered wood deck, porch or other surface.
Brush loose lichens off the wood surface using a stiff-fibre scrub brush. Detach as much lichen as possible.
Fill a 2-gallon plastic cleaning bucket with 1 gallon of warm water. Mix 236ml. of oxygen bleach into the warm water until the powder thoroughly dissolves. Oxygen bleach is powdered, nonchlorine bleach that eliminates lichens, algae and other organic growth without harming wood or the environment.
Disperse the solution liberally over the remaining lichens on the wood using a mop. Let the solution sit on the lichens for 10-20 minutes. The oxygen ions require adequate time to work.
Scrub the wood vigorously with the stiff-fibre scrub brush until the remaining lichens break loose from the wood.
Rinse the wood thoroughly with a garden hose. Fully rinse the loosened lichen residue and oxygen bleach off the wood surface.
Substitute a clean broom for the stiff-fibre scrub brush.
Do not use chlorine bleach or fungicides on wood; they can discolour natural wood.