There are deck washes and deck cleaning products that claim to remove stain. We have yet to see one that has worked very well. The only product we know of that will remove stain and not damage plants or windows is a commercial grade floor sander. Because cedar is a softwood, the power sander works very quickly. Unfortunately, this approach does not work well for railings. If you are successful in removing the stain, we would not recommend leaving your cedar deck untreated. We would coat it with a transparent sealer that contains UV protection and a fungicide to prevent the growth of mold, mildew etc.