Tracey,
DH and I sprayed clear polyethurene(sp?) on all of our wicker. You can get it in gloss or matt finish. It will probably need to be reapplied every few years. Our's held up well for the past year in all sorts of weather.
......Jan
(Make sure you buy the kind that's meant for outdoors).

Neatsfoot oil ! Waterproofs and can not crack or peel.

There is good ole Thompson's water seal.
I have no wicker but this stuff might work and it certainly is cheap.

Hi, I also have wicker chairs and I used Minwax spray fast-drying Polyurethane. The spray made for easy application. Use more than one coat if necessary. I believe it comes in different finishes. I also used this for my metal swing set and wrought iron outdoor furniture to prevent them from rusting. I have had two summer's use and still looks great. Hope this helps. Good Luck...iannilin

I bought a really good set of wicker.I have had it many years.wicker needs to be rinsed occasionally.to rid of dirt.I was told by manufacturer to not use oil as dirt,dust collects in it making the wicker weak.Was also told too much water isnt good I have mine in screened in patio.also hubbys a builder Thompsons is worthless thats why its cheap.Dont waste your money.

Thompsons is 'worthless' in the same way car wax or flour wax or furniture wax is 'worthless'.
It does need to be reapplied reasonably often.