Things You'll Need
Moss and algae killer
Lichen is a type of fungus that grows with bacteria or algae. It looks like a rough, powdery stain on a driveway and the color depends on where you live. Lichen colors include whites, tans, browns, grays, reds and greens. The spores find their way to small cracks and crevices on an asphalt driveway and begin growing. It thrives when its intricate balance of light and humidity is optimal and disturbing it interrupts the life cycle and destroys growth.
Attach a garden hose to a bottle of moss and algae killer. Remove the screw cap from the algaecide and twist the hose onto the bottle. Moss and algae killers are also available as ready-to-use or a powder mixed with water.
Spray moss and algae killer onto the lichen-stained area of the driveway. Moss and algae killers come in both chemical and organic forms.
Allow the solution to remain on the asphalt surface for the length of time prescribed by the manufacturer. Time can be anywhere from 4 to 12 hours depending on the brand. This allows time for the solution to kill the lichen.
Spray the driveway with a garden hose equipped with a high-pressure nozzle set to the strongest setting until lichen washes away. If removal is difficult, brush the driveway with a stiff bristle broom to loosen lichen and then resume spraying. Use a pressure washer if you have access to one.
Allow the asphalt to dry fully and then reapply moss and algae killer to prevent further growth.
After cleaning lichens from the asphalt surface, consider sealing the asphalt with a driveway sealer. Sealants seal small cracks and crevices and prevent spores from settling in and growing.