Store outdoor plastic wicker furniture in a shed or garage over the winter to protect it from extreme temperatures. Very cold weather can make it more brittle.
Wash plastic wicker furniture upon bringing it out for the summer. Fill a bucket with warm water and add two squirts of liquid dish detergent. Dip a sponge in the detergent solution and scrub the furniture. Rinse thoroughly with a garden hose. Dry the furniture if you have hard water so mineral deposits don't develop.
Sprinkle baking soda on stains and wait 10 minutes. Wipe the stains with a damp cloth. Use a toothbrush to scrub crevices and cracks. Rinse with the hose and dry.
Store plastic wicker furniture out of direct sunlight if possible to avoid fading. Occasionally move the furniture throughout the season so it wears evenly.