Let’s talk about seed expiration dates, how long seeds last, how to test seed germination rates, and best practices for seed storage.
Many people (myself included when I first started gardening) are shocked to learn that seeds last a long a time and do not go bad or expire. In fact, seeds can last for years if stored properly!
Seeds are perfectly designed little packages of life. They are able to be stored dormant for years and awakened under the right conditions to sprout and grow into the beautiful plant they were always meant to be.
I find it pretty amazing that seeds planted in the fall lie dormant all through winter only to burst into life in the spring!
What About The Expiration Date on My Seed Packet?
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If you have bought a packet of seeds, you may notice that there is an expiration date on the back of the packet. This date tells us what year the seeds were packed for, not when the seeds “go bad.”
Seed companies are required by law to sell new seed every year and to tell the consumer what year the seeds were packed. That’s the real reason for the “expiration date” on seed packets.
Actually, when stored under the right conditions, seeds will not go bad or expire. They can be sprouted years and years later!
My oldest seeds are from 4 years ago, and I was able to successfully grow out those seeds this year.
Older seeds can take a little longer to germinate and viability (a seed’s ability to sprout into a seedling) does start to decline year after year. However no one needs to throw out old seed packets just because they have passed the sell-by date.
Instead, keep your seeds from year to year and test your germination rates and seed viability before rushing out to replenish your seed stash.
After all, the cost of replacing many packets of seeds would be too high to do every year and what if you have special seeds that are difficult to find in stores year after year?
How to Test Germination Rates and Seed Viability
There’s an easy way to tell if seeds are still good. First, look and see if the seeds are plump, firm, and smooth (if the seed was normally smooth to begin with).
If you see mold, desiccation, or any signs of decay, then your seeds have likely gone bad and will not germinate well.
Second, test your seeds’ viability.
To test seed viability, you can follow these 4 easy steps.
- Moisten a paper towel. Put 10 seeds on the paper towel. (I’m using more than 10 seeds in the photo because I’m actually pre-sprouting these seeds to plant right away, not for germination testing! But the process is the same!)
- Spray with a fine mist of water and fold the seeds up in the towel.
- Place the paper towel and seeds in a plastic bag. Check daily to make sure the towel is moist and seeds have good contact with the paper towel. You should start to see a little tail coming out of the seed—that means it’s germinating. Germination for healthy seed should occur between 1 to 2 weeks. Check your seed packet to know when you should expect to see germination by.
- Finally, count how many seeds germinated. Multiply that by 10 and you have the germination rate percentage for your packet of seeds.
So if eight seeds germinated, you could assume that the packet has an 80% germination rate, which is a very good rate for any seed packet.
The seeds used for your seed viability test don’t have to be wasted, either.
You can plant these germinated seeds right away, and in fact it is a good way to ensure that you are planting viable seed from the get-go.
How Long Do Seeds Last?
Seed longevity depends on the type of seed. Some seeds have a thicker skin and can remain impervious to the elements for longer, thus lasting in storage for a longer time. Other seeds are more sensitive to light and moisture and will not last more than a year.
I’ve compiled lists of common vegetable, flower, and herb seeds and their life expectancy from these sources: High Mowing Organic Seeds, Clear Creek Seeds, and Fedco Seeds.
To be honest, I’m not sure how seed longevity is measured or how they can get an estimate down to the year. In my experience some of these seeds have lasted longer than the listed date, but others are spot on, so use the chart as a guideline, not a rule.
I do know that proper seed storage is essential for making sure seeds maintain viability. Taking good care of seeds can help them last a long time.
Ideal Seed Storage Conditions
On the outside, seeds don’t look alive, but in fact, they are! Seeds, although dormant, are very much full of life and will react to their environment.
Keeping seeds in their ideal storage conditions is probably the most important factor for viability, even over age.
Think about what seeds need to sprout: warmth, moisture, and sometimes light. To keep them from sprouting, give seeds the opposite.
Seeds need to be kept clean and dry in a dark, cool location to maintain dormancy and vigor.
Seeds should be stored as cool as possible, without freezing. Some people do keep their seeds in the freezer, but I just keep them in an unheated closet and that has worked fine for me for the last 4 years.
Make sure your seeds stay nice and dry wherever you decide to keep them. Under the sink would be a terrible place to store seeds!
You can include those little silica gel packs with your seed packets to help keep them dry. Those can be bought here, or you can save the packets that come with new pairs of shoes or packed with new clothes and reuse those.
Also make sure that they were nice and dry to begin with especially if you saved your own seeds like zinnia seeds! A little moisture in your seed storage container could cause mold and deterioration.
Lastly, total darkness is ideal for long-term seed storage.
Good Places to Keep Seeds
Good containers for storing seeds include:
- photo box organizer
- mason jars
- plastic bins with lids
- metal boxes or cans with lids
The photo box organizer is my favorite way to keep seeds stored and organized. As my seed collection has grown and expanded, I’ve really liked being able to keep them organized and safe in this organizer.
I also discovered these beautiful seed boxes this year if you are looking for new, fresh seed and want an organizer to keep them in. I featured these boxes in my gardener’s gift guide if you want to check out the full list.
What to Do With Old Seed
Old seeds can be composted, scattered to the winds, given to squirrels, or chaos-planted. Really, you can do whatever you like with your old seed.
The only thing I cannot do with seeds is throw them away!
A Note About Pelleted Seeds
Pelleted seeds are seeds that have been covered with a water-soluble coating. This makes them easier to handle and easier to sow.
Because they have been coated, their viability goes way down right away. Pelleted seed are really only good for one year, so it’s best to use all pelleted seeds in the same year they were bought.
Take Care of Your Seeds
By taking care of your seeds, one packet can last you several seasons. There’s no need to throw out seeds past their sell-by date and buy new ones every year. Just remember to keep seeds cool, dry, and in a dark location until you are ready to plant them.
Check over your seeds once a year to make sure they are in good condition.
Do your best to plant your oldest seeds first so you can get the most use out of every seed packet.
If you want to learn more about seeds, I also wrote a post exploring the differences between heirloom and hybrid seeds and whether one is better than the other.
I hope these tips on making seeds last help you become a more successful gardener this year!