How long do insecticide, herbicide, and fertilizer concentrates last? I have lots of each - some bought cheap at garage sales. Do they retain potency?
The thing is different chemicals have different life expectancies. Fertilizers tend to lose nitrogen to the air if left open, but the other ingredients remain intact. I've noticed that year old Grass b Gone doesn't seem to be effective, but other weed killers last for years. That's about the extent of my knowledge, but none the less I use lots of old stuff although I don't normally use insecticides and am going mostly organic on fertilizers.