If exposed to the elements and left untreated, bamboo will gradually develop a grey patina. Treating it annually with oil minimizes this color change but isn't required to retain its durability and resistance to the elements.
To revitalize bamboo's color, use Golden Care wood cleaner or wash it with warm soapy water using a sponge or soft brush and allow it to dry. Buff the bamboo with a thin coat of Golden Care wood protector for bamboo/teak or a synthetic penetrating decking oil.
If mildew has developed on bamboo, clean it using Golden Care wood cleaner or a household mold & mildew cleaner. If the mildew leaves a stain, use a bleach-based household cleaner and a pot scourer to remove the mildew. After cleaning, always rinse the bamboo off thoroughly with clean water.
Cover furniture or store indoors when not in use to extend its life.