estimating viability: how long do seeds last?

Seed-Viability2015editNO WONDER I AM CONFUSED ABOUT how long seed lasts; every expert has a slightly different take on the matter, making memorization of any absolute rules impossible. As I’ve been looking through my on-hand supply of leftover vegetable seeds, in particular, I kept saying to myself, “Now does lettuce last two years or five?” and knew it was time once and for all to make a handy reference chart comparing how long different seeds last, according to whom.

Most seed will last a couple to several years—but there are disclaimers to even that general a statement. As living things, seeds are perishable, particularly if not kept cool and dry (such as in a tightly sealed jar in the refrigerator or freezer). Humidity, in particular, is death to seeds.

Treated and pelletized seed will also have a different shelf life from seed in its natural state. The condition of the original crop the seed was harvested from will also, of course, affect its perishability.

The years of viability in my chart above, then (citing Fedco and Johnny’s Selected Seed catalogs, and the Iowa State and Virginia Tech extensions) are averages, not guarantees—and all presume responsible storage tactics (not that you left the packet in a wheelbarrow in the garage all summer, or in your overalls pocket).

SO WHERE IS THERE CONSENSUS? Onion seed lasts just a year, everyone seems to say, with parsley and parsnips other very short-lived in storage. Muskmelons last about five years; watermelons slightly less. Corn about two, maybe three, and likewise for peas and beans. But you can see the disagreement around things like lettuce (some say two, some six years) and spinach (one to five).

The best way to be sure if your leftover seeds are viable: Do a germination test. But this is tricky when you bought some great heirloom pumpkin and there were just 20 seeds in the packet and now only half those remain. (One caveat: Just because a seed is viable–can sprout–doesn’t mean it’s got enough vigor to thrive through to maturity or harvest. More on that at this link.)

Next best is an educated guess based on what’s the date on that packet, and how carefully you cared for it the last year. Safest of all: the educated guess and a backup supply of anything where you might be caught short if the calculation proves wrong.

If it turns out you don’t need the new backup seed, you can always use it next year. Well, unless it’s onion.

more help from expert sources:

  1. Vickie says:

    Thank you for all the information you share. What a wonderful way to spend gray, cold days when I can’t plant or play in the dirt as I call it. I’ve been through several of your pages on seeds, plants and gardening plans and will soon get a head start on your freezing and canning pages. Enjoy your winter days planning, dreaming, and getting excited about this years planting, progress and harvest. I’ve also enjoyed the articles and such on birds!

  2. Marcia A Chambers says:

    I love seed catalogs and ordering new stuff, yet, there is this box in the back with packets of seeds. I really need to sort this out. Thanks for all your information. You are a breath of fresh air.


  3. Tina says:

    Onion seeds are always said to be good for only one year. Last year I had a package that expired 4 years ago. I sprinkled the whole package on a ‘flat’ of potting mix, assuming a couple might germinate, but every single one germinated! I had onions out the kazoo. No special storage here, even would say bad storage, old farm house, inadequate air conditioning, tons of humidity. I no longer pay attention to the age of seeds.

    1. margaret says:

      Well, apparently you have discovered some secret to onion storage in spite of the seemingly “wrong” conditions, Tina! Happy to hear.

  4. JimB says:

    In all my 50 plus years of gardening I have never given any credence to seed longevity lists with perhaps the single exception of parsnip seed which I can keep perhaps two or three years at most. A very long time ago I learned to keep my seed 24/7 in freezer storage in zip lock bags. It only comes out of the freezer for a very short time for planting or for inventory in December or January. Many of my seeds are well over 10 years old (including onions) and germinate with vigor. I can’t say I’ve kept seed 15 or 20 years because generally I use it up before that much time goes by. My garden is 10,000 square feet and my seed inventory is large. Every once in a while some individual seed doesn’t germinate but because I plant many varieties of each vegetable or flower, the loss of one doesn’t hurt very much.

  5. sandy says:

    Is there a way to tell if a seed has been treated with a systemic pesticide? I know that certified organic seeds are neonic free, but what about the rest? I have some old cosmos seeds that do not say certified organic, but look good. is there a way to tell?
    thanks so much!

    1. margaret says:

      You’d have to trace back to the source of the seed, I think–not the seed catalog you bought it from, which doesn’t reveal much, but who grew it for them and how (conventional or organic practices), and then how they processed it before sale. Not sure such forensics would be possible now, with leftover seeds, but this is one reason I like to shop for organic seed only (and from companies who are not shy about telling me where/how their seed was grown). I wrote about that a few springs ago in The New York Times and elsewhere.

  6. Jo says:

    Margaret, the URL that follows your comment, “just because a seed is viable doesn’t mean it’s got enough vigor to thrive through to maturity or harvest. More on that at: ____” doesn’t work for me, and there isn’t enough info in the link to try to Google it. Can you direct me there in some other way? Thanks! Jo

    1. Jo says:

      Whoops, it worked when I used the link in your article online, just not when I typed the URL that appeared when I printed out your article. Interesting. I think this differences between viability and vigor may explain a few prior experiences — although who really knows for sure… Thanks for these articles.

  7. Deb says:

    Thanks. This is helpful. I agree about the onion seeds. They don’t do well , not as healthy. But, you can plant them close together and grow as “young onions”, bunching type. Not all varieties work… but it’s worth a try.
    The Thrifty New Englander!!

  8. Minnie says:

    Thanks for this chart compiled from several sources. I’ve pulled out my late spring/early summer seeds to see what should be replaced. This helps.

  9. Beverly says:

    I take all my questionable seeds of brassicas, salad greens, beets, peas, etc. and sow them in flats for micro greens. No waste and a nice supplement to my salads.

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