Most seeds are able to germinate at least 2 to 3 years after harvest if they have been kept dry and not too hot; some in fact are good for 7 years or more. And what gardener has not found an old pack of seeds left in some forgotten corner, seeds you suddenly want to try again? But if you sow them and they don’t come up, you’ve wasted pots full of potting mix and lots of time for nothing. Isn’t there are way to test the germination of seeds before you sow them?
Yes, there is. And it’s very easy to do.
A few weeks before the intended sowing date, place ten seeds on a piece of moistened paper towel and fold the paper in half, covering the seeds. Now place the paper inside a clear plastic bag, seal it and move it to a warm location. After 3-21 days (depending on the type of seed), you should have germination… if the seeds are indeed still alive.
If 7 or more seeds germinate, the seeds are still in very good condition and you can sow as usual. If 4-6 seeds germinate, their germination is below par, but still reasonable: sow them twice as thickly as you would normally do. If 3 seeds or less germinate, the seeds are really past their prime and, unless the variety is irreplaceable, it is probably not worth sowing them, as the seedlings will probably germinate at an even lower rate when sown in soil and, even if they do come up, will tend to produce weak or unhealthy plants.