I don't want to get into the middle of an argument, so I will keep my opinion of bleach to myself (which is not difficult as I am allergic to it anyway), but I'm pretty sure that the picnic table in question has legs made of treated wood and the top/table part is untreated wood.
Rather that do all this stuff only to end up with a rotten-top table, why not replace the top of the table? Before adding the new wood, you can treat/seal/stain it as the table will not be used for picnic purposes but for plant storage and needs to be sealed against moisture.
Okay, that's all I have. Good luck.
