Blue water shouldn't hurt anything. My grandfather spoke of throwing dish water out of the kitchen door on the kitchen garden. The concentrations should be too weak to be harmful. Sometimes we get TOO careful. Nature can do a lot in spite of us. A cheap water saving trick is to put four sheets of old newspaper down, cut an x and insert the plant. I say four sheets because that will still allow moisture penetration and will rip rather than pull up the plant if a tiller blade hits it. It will also biodegrade nicely by Fall. This also helps ontrol soil borne diseases which are spread by splashing. Chuck Wyatt