I have most of mine potted up also and use a Hugelkultur approach to combat moisture loss. Take an oak log, about 2" smaller in diameter than the pot and short enough to leave planting room, and place it in the bottom. I then like to use larger pine bark mulch as a "filter" to keep the potting mix from washing out the drainage holes around the log. I don't think a few drops of Dawn or Joy will affect anything as a lot of people use them a "spreader sticker" when spraying chemicals.
