The Shelf Life of Seeds - How long do they last?
Did you ever throw a seed packet in the garbage, frustrated at the idea that you could not possibly grow that many plants before the expiration date?
Let me tell you a little secret. You were right to feel frustrated! Seeds do not have an expiration date.
What they do have is a sell-by date, which is dictated by the Federal Seed Act. This federal law regulates important aspects of the vegetable and flower seed trade, such as the minimum acceptable germination rates, testing and information. As a general rule, all vegetable seeds commercially sold in in the United States must include the same basic information on the seed packet.
This information includes the type of seed and common trade name, the scientific name (latin name) as well as the days to harvest or bloom, the light requirement as well as the frost hardiness. Most seed packet will also indicate if the plant is a perennial.
The last piece of mandatory information that has to appear on the seed packet is either the year those seeds are intended for sale OR a germination rate and test date. Any of those two choices can appear on your seed packet and be compliant with the regulation. A seed packet’s sell-by date is dictated by the date the germination test was performed. All vegetables and flower seeds lots have to be tested to ensure they meet the minimal germination rate established under the Federal Seed Act. This testing is done either by the seed company producing the seeds or by an approved laboratory. All seeds from the same seed lot have to be sold within 12 months of the conclusion of the test.
Here’s where a lot of new gardeners make a costly assumption. The sell-by date is a law that applies to the sell of the seed but has little to do with their viability. In fact, a seed packet stored improperly in a damp and warm environment is likely to have few if any remaining viable seeds after a few days while a seed packet store in its original packaging in the dark, cool space of a air-conditioned closet will remain intact after many years.
You see, seeds are not aware that this sell-by date hangs over their heads like the proverbial sword. They simply lay in their packet in a dormant state, waiting for the right conditions to germinate and grow.
So, when the season is over and you look at all those unused seeds left in your old packets, by no means does it mean that they will not germinate and produce valuable crops for the next season and possibly many more years to come. It simply means that the seller must not sell those seeds past it. This sell-by date is set to ensure the buyer that the seeds from the seed lot tested will retain their original germination rate if stored at typical storage conditions.
But exactly how long are they viable for? Well, it all depends! Each type of seed has its own viability, which will vary with the storage conditions. Most people know to keep their seeds in a dry, cool and dark environment and this is to keep the seeds in their dormant state for as long as possible. Humidity is the main culprit for seed decay as mold will kill the embryo inside the seed and ruin the germination rate. I chose to store seeds for my personal use in their paper seed packet, neatly sorted in plastic craft storage boxes and tuck them in a closet in my house where they are protected from the light and kept at a relatively stable temperature.
Perform a home germination test
I usually don't bother with a germination test for seeds that germinate fast such as lettuces, radishes and kales or that require to be direct sown such as carrots.
I do, however, perform a simple germination test for seeds that require a longer time to germination or those that are older in my seed collection. For example, I regularly test the germination rate of my pepper, eggplant and tomato seeds as those require transplants where I live and I cannot afford to lose my precious indoor growing space on seeds that have little chance of germinating.
Here is the simple test I perform for my own seed collection. What I like best about it is that I do not waste those precious seeds, but simply sow the newly germinated seeds into compost and place them under grow lights.
Seeds needing light to germinate (non-exhaustive list!)
- Brussels sprouts
- Chinese cabbage
Seeds needing darkness to germinate (non-exhaustive)
How to Store Seeds Properly
Seeds need to be kept dry and cool. The most important factors in seed storage are seed moisture and storage temperature. The drier the seeds at time of storage, the longer they can be stored.
If the seeds are exposed to too much moisture and warm temperatures they will begin to sprout. Once the seed has sprouted, the process cannot be reversed. If the seeds sprout while in storage, they will not grow the next year when planted.
But I also have another trick up my sleeve for rare seeds that need to be protected at all costs and keep their germination rates intact for a long period of time. First, I dry them thoroughly in a dehydrator, then store them in sealed mylar bags intended for long term storage. I then place them in the freezer. This is a very good, home-gardener friendly way of simulating the long term storage type that is seen in the more ambitious seed vaults from different agencies across the globe.
Just make sure to allow the seeds to go back to room temperature gradually before opening the bag after taking them out of the freezer. The key here is to avoid the seeds from become moist with condensation.
Did you grow old seeds into successful crops? Do you have any other tips and trick to share? Leave a comment below and we will make sure to answer and share with our readers!
SOURCES Colorado State University Extension. Storing Vegetable and Flower Seeds 7.221. J. E. Ells, L. N. Bass, and D. Whiting. Updated May 2020. https:// extension.colostate.edu/topic-areas/yard-garden/ storing-vegetable-and-flower-seeds-7-221/
Iowa State University Extension and Outreach. Life Expectancy of Vegetable Seeds. J. Romer. Apr 1999. https://hortnews.extension.iastate.edu/1999/4-2- 1999/veggielife.html
Illinois Extension. Test Seed Viability. N. FlowersKimmerle. Feb 2017. https://extension.illinois.edu/ blogs/rhonda-ferrees-ilriverhort/2017-02-03-testseed-viability