Keep the furniture out of extremely wet conditions. Although there is a natural amount of moisture in the vines used to weave wicker furniture that keeps it pliable, they can be damaged by mold and mildew if continuously left outside in wet conditions from rain or dew. Follow your local meteorologist's weather reports and secure a plastic tarp over your wicker furniture if heavy rain is predicted. Wipe down any wet furniture with dry, clean cloths when necessary.
Clean dirt and grime from the furniture as it appears. Spray down the wicker with a garden hose to rinse away light dust and dirt. Use a sponge and liquid soap with warm water to wipe down heavy amounts of dirt on the wicker. Rinse clean with a garden hose and dry with a cloth -- or leave the furniture in the sun to dry naturally. Move the furniture out of direct sunlight once it is completely dry. Direct sunlight dries out the natural moisture in the reeds, leaving it brittle and open to breakage.
Bring wicker furniture indoors during cold winter months. If this is not feasible, securely cover the furniture with a plastic tarp to protect the wicker from the cold-weather elements.
Use spray paint that matches the wicker's paint color to cover spots where any paint has worn away. The paint provides protection to the natural wicker beneath.
Clean synthetic wicker -- such as aluminum, resin or plastic -- with soap and water and allow to air dry. Man-made materials are not affected by prolonged exposure to environmental elements such as sunlight, heat and rainwater that tend to fade and rot natural wicker.