Why It Grows
Cedar wood consists of cellulose, a substance contained in the cell walls of all plant materials. Cellulose provides an ideal nutrient for many mold varieties, according to the Centers for Disease Control and Prevention. To exacerbate matters further, cedar contains high porosity, meaning that it can absorb and trap moisture. The combination of moisture and cellulose provides mold spores with everything they need to grow and multiply.
Controlling Humidity
Mold can grow on cedar when high relative humidity exists. The high humidity results in a moist atmosphere due to the excessive water vapor. The vapor clings to the porous cedar and can contribute to mold growth. You can control this problem indoors (for objects like cedar dressers and chests) using a portable dehumidifier. If you have high humidity outdoors, paint objects like cedar decking with a fungus-resistant paint to prevent mold growth.
Other Factors
Water damage can contribute to mold growth on cedar. If flooding occurs, or if your cedar becomes exposed to high levels of water for any reason, dry the object using heat. Use sunlight if possible, otherwise use a heating device like a space heater or hair dryer. Using towels will not do the trick, as a result of cedar's high porosity. Also keep your cedar objects clean. Dirt accumulation can contribute to mold growth, according to a report from the University of Missouri Extension.
Removing Mold
If mold has already appeared on your cedar surface, first dry the surface thoroughly. Afterward, spray it with a solution of 50 percent bleach and 50 percent water. Wait about 10 minutes, rinse the cedar and dry again. If you object to using household bleach due to the fumes or environmental concerns, you can use oxygen bleach powder, activated with water according to the manufacturer's instructions.