I would like to prepare an old deck for staining. Scrubbing with a bleach solution seems a popular technique. Will the bleach solution harm nearby plants? What about if I use soap instead?
Yes bleach will harm or kill some plants - most plants it is just the leaves. I use a bleach/weed killer combo on poison ivy and it basically clears out everything in its path. If your plants get bleach on them the very best case scenario is you will notice spotting.
Soap is perfectly fine around plants. Maybe there are some very sensitive plants that may have a small small effect on - that is more of a gardening question though. Unless you are dumping gallons of soap on your plants they will be fine - might smell different though.
I use bleach to kill any algae or fungi on the floor of balcony. After using bleach, it becomes perfect at least for a couple of years. So imagine how it can kill anything. You have to think that Chlorine is the primary disinfectant for the house, the pool and all kinds of disease. The unic one for fungal diseases. It kills any organic cell.
"It has the highest electron affinity and the third highest electronegativity of all the elements; for this reason, chlorine is a strong oxidizing agent."
I agree with soap, but you have to use Marseille soap or by the way a natural one (home made). Otherwise, normal soaps contain caustic soda, which also kills the plants.