Does fertilizer go bad? It's about time to weed&feed, but I have a small area I also need to seed and I want to just put fertilizer with the seeds, not the stuff for weed control, right? I have 1/2 a bag of lawn fertilizer in the garage, it's been kept dry, but it's 3+ years old or so and I was wondering if it's any good or if I need to buy new.