I was told to use a 0.1% mix when soaking seeds prior to germination, or when watering seedlings. This cleans the seed surface and discourages mold, fungus, and damping off. Drug stores sell 3% Hydrogen Peroxide, so dilute that 32:1. It is also great for plants already in the ground or in containers.
I have used it stronger myself without any harm. If the roots are already rotted, I never brought back a plant.
Please tell your stories for us.
Stush