Keep your vintage wicker furniture indoors or on a covered porch away from direct sunlight to prevent it from fading and becoming brittle.
Vacuum the furniture regularly, using a hose with a brush attachment. If there is a lot of dust or dirt built up on the furniture, brush it with a soft scrub brush, nail brush, and a toothbrush to loosen the dirt before you vacuum.
Wash the wicker a couple of times a year with warm water and a few drops of mild dish soap. Use a soft sponge to get the soapy water into the weave, but don't let it sit for more than a few minutes. Rinse the wicker well with a garden hose, and dry it with towels. Then allow the furniture to air-dry for a day or two.
Remove mildew from wicker furniture by scrubbing it with a solution of 3/4 cup of bleach and 1 gallon of water. Rinse the wicker thoroughly with a hose, dry it with towels, and allow it to dry for several days before you use it.