If this is not your first year gardening, you probably have some extra seeds from last year (or years before). The question is: are the old seeds still viable and capable of growing into healthy plants?
So, can you use seeds from last year in your garden? You can use seeds from last year – most will last for 1 to 6 years. However, germination rate (the percentage of seeds that sprout) decreases over time. Some seeds (like spinach, lettuce, and corn) won’t last much longer than a year. Others (like arugula, pumpkins, or tomatoes) last up to 6 years.
As you might have guessed, the viability of seeds is affected not only by age, but also by factors such as plant species, variety, and storage conditions (like temperature and humidity). Let’s take a closer look at how long seeds will last, how to test germination rates, and how to store seeds properly.
(You can watch my YouTube video on how long seeds last if you prefer!)
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How Long Do Seeds Last?
Remember that the seeds in a packet do not all expire on the same day. It is possible that one seed will lose its viability after a year, and another will remain viable for 5 years or more. Remember: the overall germination rate for a packet of seeds decreases over time.
The germination rate is the percentage of planted seeds that will sprout and have the potential to grow into healthy plants. For example, a germination rate of 90% means that if you plant 100 seeds, you can expect about 90 of them to sprout and begin to grow (less if you are unlucky, more if you are lucky!)
A decrease in germination rate will happen faster for some plants than for others. For example, the germination rate drops off quickly after one year for plants such as spinach, lettuce, and corn.
On the other hand, the seeds of some plants (like soybeans, melons, and cucumbers) can maintain relatively high germination rates for three years or more.
Check out the table below to see some examples of plants that have average storage lives of 1 year, 2 years, 3 years, and so forth (the low end is given).
| Average Storage Life (Low End) | Plant Type |
|---|---|
| 1 year | Oats, Rye, Sorghum, Artichoke, Sweet Corn, Lentil, Lettuce, Onions, Parsnip, Spinach, Anise, Dill, Fennel, Parsley, Rosemary, Sage, Thyme |
| 2 years | Alfalfa, Buckwheat, Beans, Beets, Leeks, Okra, Peas, Swiss Chard |
| 3 years | Barley, Wheat, Asparagus, Broccoli, Cabbage, Carrots, Cucumber, Kale, Soybean, Squash, Tomato, Melon |
| 4 years | Cauliflower, Chicory, Eggplant, Mustard, Pumpkins, Radish, Turnip, Watermelon, Oregano |
| 5 years | Crimson Clover, White Clover, Hairy Vetch, Cress, Endive, Strawberry |
| 6 years | Arugula |
lot on the type. You can use old seeds, but the
germination rate might be quite low in some cases.
Notes:
- the seeds of herbs and spices (Anise, Dill, Fennel, Rosemary, Sage, Thyme) last 1 year.
- the seeds of Cress, Crimson Clover, Endive, Hairy Vetch, Strawberry, and White Clover last 5 years.
- arugula seeds last 6 years.
- other seed types are shown in a graph (there is a PDF version of the graph here).
For more information, check out this seed storage guide from Johnny’s Selected Seeds.
Of course, there are ways to make your seeds last longer. If you collect and store them properly, you can increase their lifespan considerably – possibly up to 10 years or more (more on this later).
Under ideal conditions, certain seeds can last centuries or longer!
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How To Test Seed Germination Rates
If you don’t know how old your seeds are, then you might want to test them out before planting a large number in the garden. Otherwise, you risk wasting time, energy, and garden space. Luckily, there is an easy way to test seed germination rates right at home.
Start with a moist paper towel. Then, put a sample of seeds (perhaps 10 from the same packet) on the paper towel.
Put the paper towel inside a plastic bag, and leave it in a warm location, such as a sunny windowsill. After a few weeks, check to see how many seeds have sprouted.
Most seeds will germinate after a week or two, but some may need up to three weeks (this depends mostly on temperature).
If two of your ten seeds sprout, then the germination rate is 2/10, or 20%; if five seeds sprout, the germination rate is 5/10, or 50%, and so forth.
(You can learn more about seed viability and testing germination rates here).
You will have to decide for yourself on an acceptable germination rate. Remember that you can always plant extra seeds and sow them close together to hedge your bets. Later on, you can thin them out (pull out the weakest excess plants) if you get more seedlings than you bargained for.
If you don’t see any sprouted seeds at all, that’s a bad sign. This suggests one of two things: (1) the seeds were kept too dry or too cold, or (2) the germination rate of the seeds is 0%, or close enough to zero that you shouldn’t bother planting them in your garden.
As an alternative to a paper towel and plastic bag, you can use moist seed starting mix or a humidity dome to test your germination rate. For more information, check out my article on humidity domes.
For either method, just make sure to keep the seeds in a place where they are warm enough to be able to germinate.
Can I Collect & Store Seeds From My Garden?
Yes, you can collect and store seeds from your garden. However, be aware that with hybrid varieties, these seeds do not always yield the same plants that you got from the original seeds.
The next generation may be smaller and less productive than the original one, or they may produce no fruit at all! For this reason alone, you might want to consider buying seeds for the next year instead of collecting and storing your own. You may also want to purchase heirloom seeds if you can find them.
For more information, check out my article on the pros and cons of hybrid seeds and my article on heirloom seeds.
However, if you do want to collect seeds from your garden, follow the steps below. That way, you give the seeds their best chance at surviving storage so that they can germinate and grow in future years.
How To Collect, Handle, & Store Seeds Properly
To begin with, always remember to handle your seeds gently! Any rough handling can result in damage to the seeds, reducing viability, ability to survive storage, and germination rates.
To harvest seeds from your plants, wait until the seeds are mature. You may need to scoop the seeds out of the fruit (for example, from tomatoes or peppers)
After you do this, rinse off the seeds to get rid of any excess fruit flesh or dirt. Leave the seeds out on a tray or table for a few days to air dry.
According to the Colorado State University Extension, a 10-year storage life requires drying seeds so they have 8% moisture (8% water content by weight). They recommend that you dry seed at 100 degrees Fahrenheit (38 degrees Celsius) for 6 hours.
Leave seeds out in direct sunlight to do this – don’t use a microwave. If you use an oven, don’t overheat the seeds, or they will be ruined.
If you dry the seeds too much, you might produce “hard seed”, which resists germination due to lack of water absorption.
Then, put the seeds in a paper bag, envelope, or a container made of plastic or glass. Both of these have their advantages and drawbacks.
Paper bags or envelopes are good for short-term storage. However, humidity in the air can affect the seeds more easily by permeating the paper.
A plastic or glass container will keep outside humidity away from the seeds. However, any humidity inside the container is trapped inside with the seeds. If the air inside the container is not dry enough, the seeds can get moldy and spoil quickly.
Whichever container you choose, you should also add a desiccant, such as silica gel, rice, or powdered milk in with the seeds. These desiccants will draw water from the air and keep moisture away from the seeds.
You can also opt to freeze the seeds briefly, to kill any insects (or their eggs) that may be present. Either way, remember to put a label on the seed container which includes:
- the species of the plant (e.g. Tomato)
- the variety of the species (e.g. Early Girl)
- the date the seeds were collected or purchased (e.g. March 2020)
- the garden location the seeds were harvested from (if applicable)
- the days to maturity (check for your variety using a catalog or online resource)
Be sure to store the seeds in a cool, dry, dark place. A basement or cellar might be a good choice, but you could also use your refrigerator. Try to keep the temperature constant, if possible.
As a guideline, the USDA recommends that the storage temperature for seeds be less than 50 degrees Fahrenheit, and the humidity level be less than 50%. Johnny’s Selected Seeds suggests a temperature of 42 degrees Fahrenheit for seed storage.
For more information, check out this article on seed handling and storage from the USDA.
How Old Can Seeds Be And Still Germinate?
As mentioned earlier, seeds do not all expire on the same day. Some expire and lose the ability to germinate quickly. Others can last much longer than their sibling seeds.
Even if the germination rate drops to 1%, there is still one seed in a packet of 100 that can sprout and grow into a healthy plant. So, how long can seeds really last? Perhaps a decade, or maybe even a bit longer?
In fact, some seeds have been known to germinate after a century or more! In Germany, some seeds were stored in containers in the concrete foundation of a building and had a 12% germination rate after 123 years!
For more information, check out this article from the USDA on seed storage.
However, there are also seeds that are thought to have survived for thousands of years and remained viable. For example, according to Wikipedia, the oldest carbon-14 dated seed to grow into a viable plant was Silene stenophylla. This Arctic flower is a native of Siberia, and radiocarbon dating confirmed the age at over 30,000 years!
For more information, check out this article on oldest viable seeds from Wikipedia.
Conclusion
Now you should have a much better idea of how long seeds will last, and steps you can take to improve shelf life. If your old seeds don’t germinate well, you can always buy some established seedlings from a nursery to make up for the shortfall.
I hope you found this article helpful – if so, please share it with someone who can use the information.
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~Jonathon