You may notice raised bumps, a hairy coat, tiny hairs, or raised specks. These are all signs of mold and may indicate that the seeds have spoiled. A standard germination test can be performed on older seeds using paper towel germination and sachet testing. This is one of the most common methods for testing seed viability.
Seed packs usually indicate the planting year for which the seeds were packaged, as well as the germination rate. As the years go by and the seeds age, the germination rate decreases, faster or slower, depending on the variety of seeds and how the seeds were stored. A good rule of thumb is to wait approximately 10 days; however, if you want to give your seeds the best chance, research the germination time of your specific seeds. Depending on the type of seeds, the environmental conditions, and the manner in which the seeds have been stored, the germination rate of older seed packages can be greatly affected.
But I wouldn't use less than five seeds, otherwise your seed viability test wouldn't be very accurate. You can do the germination test at any time, but if the tested seeds have sprouted at the time of sowing, you can move them to your garden. Think of the dates printed on seed packages as those “Expiration dates on foods; they are not set in stone, but rather are more of a guide as to how long the seeds are at their peak viability. The key is to start with completely dry seeds (if you saved them from your own plants) and store them in airtight, freeze-proof containers to reduce the risk of the seeds absorbing moisture.
Other times it's because seeds lose their viability over time and many types of old seeds don't germinate. Also, you don't have to worry about the sample seeds going to waste, because you can plant the seeds that have germinated on the paper towel. Here's what you need to know about properly storing your seeds and what you can do to maximize the shelf life of your vegetable, herb, and flower seeds. If you like to store seeds from your garden, or have a lot of old seeds lying around, take the time to do this simple germination test on them.
But, if the seeds don't germinate on the paper towel after 4 to 6 weeks, or if the seeds are rotting, then you can throw away those old seeds or you can try another batch. Viable seeds should germinate in approximately six to 10 days, but you should check the time period indicated on each seed package. But does it work for seeds that are not cold-resistant (I would think nasturtium seeds would be ruined after freezing?). Seeds expire, but expiration dates are rough guidelines; experts say it depends on the type of seeds and how they were stored.