Treated some overwatered, root mite and gnat infested houseplants with the commonly recommended 1:4 ratio H2O2 : water mix after first letting them dry out for a couple of days. Damn if it didn't bring them back from the dead. They've gone from scrawny to flourishing, in less than 72 hours. I'm tempted to give them a light sip (tsp H2O2 per cup of water) every time I water them from now on. How much is too much?
FWIW, yes, I read the earlier posts about how peroxide is a waste of money in the garden, kills beneficial fungii, nematodes, etc. And I agree. This is for decidedly inorganic container plants, however.