When you're planting a garden, you want to make sure you're not wasting time, energy, and garden space with bad seeds. Before you go and buy all new seeds, test out what you have with a wet paper towel.
Photo by mannewaar
Seeds from all plants have a germination rate that steadily decreases over time, meaning that you have a certain window to plant them and get the most out of them. If you have some leftover seeds and you're not sure if they have gone bad, Trena Heinrich at Food52 suggests the wet paper towel test:
Take a paper towel and run it under water then ring it out. Place 3 to 4 seeds in the paper towel and place in a warm spot in your house. I usually use the top of the clothes dryer because it's used so often, but you could use a heating pad set on very low.
If you don't see any sprouts within a couple of days, the seeds aren't viable for planting anymore. Some seeds can be good for years, so don't go throwing out anything until you've checked.