To minimize mold on the decking, clean the deck as often as needed but at least twice each year. Climate conditions vary in different regions of the country and may necessitate more periodic cleaning. In some situations, you may need to repeat the cleaning process multiple times until you are no longer able to see any “shadows” of the spots on your deck while it is wet. You would also want to apply a mold inhibitor to retard future growth. Once the decking has been thoroughly cleaned, you will need to maintain it in much the same way you would adhere to a cleaning schedule for any other significant item in or around your home.