How long do seeds last? This is a question that lots of home gardeners have asked, myself included. If you like to save seeds—something else that a lot of us gardeners do—the answer to this question is pretty important. That said, there’s no one simple answer to this question. There are countless different types of seeds, and more than one potential storage method to choose. So if you’re looking for just one answer, here it is: it depends on several factors. Now, let’s get into the details of what, exactly, that means.
Geography and Environment
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Your location actually makes a difference in how this question is answered. If you live in a humid, wet climate, your seeds won’t last as long as those in dryer conditions. There’s a limit to this, of course. If you live in an exceptionally dry, arid area, your stored seeds will be negatively impacted as well. When you’re saving seeds to use within the next few years, it’s best to store them at 50 percent humidity.
That’s why it’s best if you keep them in an environment that you can adjust. Don’t store your seeds out in the garage or the garden shed, as these are areas that will be prone affected by outdoor weather and temperature conditions. You would do best to store your seeds inside your home, which is temperature-controlled.
It’s important to store seeds the right way to keep them as viable as possible. First, dry those seeds really thoroughly. Next, put them in a controlled, sealed environment. This sounds complicated, but it’s not. All you have to do is seal the seeds in a jar with a bit of uncooked rice at the bottom. This will absorb excess moisture. The sealed container protects your seeds from moisture in the air. Once that’s done, you have another very important factor to consider.
Temperature
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The vast majority of vegetables and herbs grow in spring and summer, when the weather is warm. Since warmer temperatures can jolt seeds into germinating, it’s important to store your seeds in a cool location. Once germination begins, those seeds need to be planted or they’ll be wasted. If you’re lucky enough to have a root cellar, this is a great place to store your seeds. Otherwise, keep them in a basement, in a cool closet, or somewhere else that maintains a relatively dark and cool environment.
The optimal temperature for seed storage is about 40 degrees F. Your refrigerator would be pretty perfect—but, like most people, you probably open your fridge often and have a light in there that turns on automatically. This causes temperature fluctuations, and the light isn’t good for seeds either. Do you happen to have a spare fridge in your basement or garage that gets little use? You may consider stashing your seeds here. Otherwise, scout out the coolest place you can find inside your home.
How to Test Your Seeds for Viability
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Now that you know how to store seeds, your mind is probably already preoccupied with a new, essential question: how do I know whether those seeds are still viable? There’s actually an easy way to test your seeds before you put them in the garden. This way, you don’t have to plant them and cross your fingers that they’ll germinate. When you’re ready to plant your seeds, fold about 10 of them inside a damp paper towel. Place this towel inside a plastic baggie, but don’t seal it shut. Keep that towel moist, but not soaking wet. If they’re still good, the seeds will sprout in about 7-10 days. You’ll know then and there whether you can re-plant the seeds, or if you need to get some new ones.
Once seeds germinate, you need to plant them immediately. Considering this factor, it’s best to test your seeds when you’re ready to start planting, anyway.
Average Life Span
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It would be impossible to name every single seed and list their life spans, but I can tell you about some of the more common species you’re likely to grow in your home garden. Most of your vegetable plant seeds—including beets, beans, cucumbers, onions, lettuce, and peppers—will stay viable for about two years, sometimes three. Broccoli, cauliflower, collard, kale and many other types of leafy greens’ seeds will last three to five years if stored properly.
Sweet corn, parsnip, and spinach seeds don’t last long, under even under ideal storage conditions. These will stay viable for about a year or two at best. Many flowers can also be stored for only about one year, though some varieties last as long as three. Most perennials can be stored for two years. Tomato seeds can be stored for up to 8 years. Most types of melons, pumpkins, eggplant, and squash seeds stay good for about four years, when stored well in the previously described conditions.
Of course, you can’t expect your 7-year-old tomato seeds to produce plants that are as strong and healthy as those grown from seeds you bought this year. That’s because of a little thing known as “loss of vigor”. This is something you need to know about if you plan on doing any long-term seed storing in the future.
Loss of Vigor
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Some seeds can be saved and stored for several years, but although your seeds may germinate to prove they are still viable, you won’t get any guarantees about how vigorous your plants will be. Seeds that have been stored for long periods of time—or even just over a year, in some cases—may produce plants that are noticeably less robust than those cultivated from newly purchased seeds. These plants will be slow to grow and will produce less foliage and fewer fruits, flowers, or vegetables.
Even when seeds germinate, you won’t know how much they have lost their vigor until they’ve actually grown a fair bit. You could be in for some unpleasant surprises, so it’s a good idea to always get a few new seeds for your garden to supplement those you have in storage. This way, you can guarantee at least some kind of return on the crops you tend.
More Extreme Storage Options
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All of these factors considered, the old saying “there’s more than one way to store a seed” is quite true. You do have another option if you’re thinking about some serious long-term seed storage. Most home gardeners store theirs to use the following season, and if that’s your goal it’s definitely best to follow the guidelines I outlined previously. Of course, you may have a different agenda in mind.
It is possible to store seeds for a much longer period of time—indefinitely, even. An example of this type of long-term storage is the Svalbard Global Seed Vault. Established in 2008, it’s said to represent the most diverse collection of food crop seeds ever put together. Svalbard holds around one million packets of seeds, in addition to other crop-growing materials. Housed on a Norwegian island, it was created as an insurance policy against potential global disaster. It’s buried in permafrost deep within an old Arctic mine that’s no longer in use, where the extremely cold conditions can keep the seeds viable, conceivably, for centuries. It’s considered to be a “fail-safe” seed storage facility.
So if you want to experiment with some long-term storage, put your seeds into a serious deep-freeze. Place them in a sealed container and kep them in a dark, freezing location. Sub-zero temperatures are ideal for this. But unless you have access to permafrost or an extra sub-zero freezer that isn’t used often, this probably isn’t an option.
Answers to Seed Questions
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Hopefully, you now have a much better idea of how long seeds last, and what you need to do to store them properly. If you factor in issues like loss of vigor and some seeds’ relatively short storage span, you may decide that storing your own isn’t worth the time and trouble. Saving seeds from one year to the next can be a way to defray some of the cost of your yearly seed-buying, but it can also be a time-consuming process. Many gardeners choose to store only more expensive seeds to save themselves this time and trouble.
Either way, you know what needs to be done in order to properly store yours. Try it for yourself, and you might decide that the time and effort it takes to store them the right way is well worth it. A good way to determine if this is really cost-effective for you is to make a little list of the type and number of seeds you typically purchase each year. Then, write down the price you paid for them, or approximate said cost by looking up seed prices online. If saving seeds from your garden reduces your annual costs, then it’s well worth the time and effort to do so.
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