How Long Do Seeds Remain Viable? Try a Germination Test
Although seeds may look the same at first glance, after a certain period of time, you won't see any seedlings sprouting. Over time, the ability of seeds to germinate gradually decreases. Seed germination rate generally varies among different plant species, but it also depends on the maturity of the seed at harvest time and storage conditions. A fully mature seed stored in a dry and cool place will maintain its germination ability the longest.
The Champion in Maintaining Germination: Melons and Pumpkins
If you find forgotten melon, pumpkin, zucchini, or cucumber seeds from the year before last at home, don't be afraid to use them this year. If you don't store them somewhere in a damp cellar, they will reward you with a delicious harvest even after 6 years of rest. Radish, pea, brassica, tomato, or beetroot seeds are also often in full strength even after 4 to 5 years. Carrot, celery, lettuce, spinach, or bean seeds will maintain their germination ability for approximately 3 to 4 years. For parsley, seeds must be used within 2 to 3 years from harvest. With chives, onions, or leeks, you need to hurry even more and use the seeds the following season, or at most the year after.
Germination Test + A Little Math Review :-)
To perform the test, besides seeds, you will need a bowl (a deep plate will suffice), fine sand (or alternatively cotton wool or paper towels), water, and food wrap. At the same time, you'll practice calculating with percentages, which is useful at any age.
Select a test sample from the seeds (e.g., 10, 20, 50, or 100 seeds) and note their number. For larger seeds, a smaller test sample is used; for species with small seeds, increase the sample size. The more seeds you use, the more accurate the result will be. Spread moistened sand on the bottom of the bowl or plate, into which larger seeds should be sown so they are slightly covered with sand. Smaller seeds just need to be sprinkled on the surface, or even better, first arrange them on a paper kitchen towel, which you then place on the wet sand. For smaller seeds, you can skip the sand entirely and use a layer of cotton wool instead. Smaller seeds can also be covered with a damp paper towel from above. Then cover the bowl with perforated wrap and don't forget to keep the seeds moist. The ambient temperature should be between 18 and 20 °C.
The seeds now have about 10 to 14 days to show what they can do. For seeds that are in good condition, at least 75% of the seeds will germinate. If only half germinate, you can still use them, but you'll need to perform a denser sowing. In case of germination rates significantly lower than 50%, we recommend getting new seeds. The easiest evaluation is with a sample of 100 seeds, where the number of sprouted seeds is also the percentage expression of germination rate. For samples of other sizes, the percentage figure needs to be recalculated.
Proper Seed Storage is the Foundation for Successful Germination
Buying too many seeds in advance doesn't pay off. When purchasing, it's important to check the expiration date indicated on the seed packet. Therefore, definitely don't throw away the original packaging before using the seeds. For seeds from your own harvest, don't forget about airtight storage and precise labeling of the species (ideally including the variety) and harvest year. Seeds thrive better in cool conditions. Well-dried seeds in airtight packaging can be stored in the refrigerator or even in the freezer. When stored under ideal humidity conditions and at a temperature of -18°C, some seeds can remain viable for more than 20 years.