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Generally seed packets have some kind of expiry date on them. I've got "sow by" dates on my packets of Suttons seeds and "best before" on Unwins.

Is it worth sowing seeds which have passed their expiry dates? And would the answer vary from plant to plant (e.g. can I be more relaxed about expiry dates for plants that are "easy" to grow, like salads and radishes)?

Also, if I persist with out-of-date seeds, will the results consist of:

a) fewer successful germinations

or

b) weaker, less productive adult plants

or both?

Is there any evidence seed companies apply these expiry dates cynically, in order to generate extra sales of newer seeds?

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I had a half pack of basil seed which is more than 1 year age. I sowed all of them weeks ago accidentally, and none of them sprout. LOL. –  lamwaiman1988 Sep 2 '11 at 8:57

3 Answers 3

up vote 10 down vote accepted

According to "Seed to Seed" by Suzanne Ashworth, p29:

Always realize that seed vigor can be lost during storage well before the seeds die completely. For example, if a seed sample germinates at only 20%, that doesn't mean those seeds which sprouted would have grown normally. That sample's seed vigor has diminished to the point that 80% of the seeds aren't even strong enough to sprout, and the remaining 20% will have so little strength that they probably will grow weakly and may not even reach maturity. Constantly keep in mind that your seeds are living entities and will only grow strongly during subsequent seasons if you do everything possible to see that they are stored in truly excellent conditions. Strong plants in the garden are partially a reflection of good seed storage techniques.

So to the second part of your question, yes, you can get reduced germination rates and weaker adult plants.

But if the seeds have been stored well (in a cool place with stable temperature, away from light, and very dry) they may still be strong. If you have enough seed to spare for a test, it's worth doing a germination rate test as described in Peter Turner's answer so that you can get an idea of whether it's worth the effort and space in your garden. Some seed is so cheap (or you need so little) that it's better to toss the old seed and buy fresh.


Re: does it vary from plant to plant? Yes, but it's not based on how "easy" the plants are to grow. See the longevity table in this article. For example, onion seeds do not store well: germination drops off a lot after 1 year. But endive or cucumber can store for 5 years. And if you keep your seeds very dry and cool you can store them for even longer.


Re: "apply these expiry dates cynically, in order to generate extra sales", I don't know of any evidence. But I'm guessing many casual gardeners aren't storing their seeds in ideal conditions, so the "sow by" date you see is probably legitimate. Good seed companies will mark the date and percentage of the last germination test on the packet. Use a chart like the one linked above to decide for yourself (or perform your own germination test) if the seeds are still good.

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Less germinations would be my experience. Once the seedlings get a good start, then age of the seed is almost certainly irrelevant compared to growing conditions (nutrients, water, sun, etc).

Is it worth it? I would say yes as you don't lose anything. However, if you are short of space, you may want to use more productive seed instead.

A few months ago I planted some old red yucca seed which I found in the shed. I don't have anything to compare against, but as we'd forgotten where they came from, they are "old". Planted them on the off chance and some are coming up. So in a few years I'll have lots of yuccas and not know what to do with them!

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1  
yucca fries or chips. –  wax eagle Jun 10 '11 at 20:44
    
I'd have to look into those. I'm not sure if these are fleshy enough? We'll be able to plant some out, and give others away. They're a local wild plant. Perhaps they could make a low 'hedge' to keep mammals of the two legged type out :-) –  winwaed Jun 10 '11 at 20:49
    
I was confused there is a plant called yuca in Spanish that is cassava or manioc. Its a tuber that is used for fries and chips among other things.. –  wax eagle Jun 10 '11 at 23:56
    
Sorry yes mine are Texas Red Yucca. Grows wild locally, and turns out to be a 'false' yucca: laptopgardener.com/?p=723. Getting quite fashionable around here, so they'll probably be passé when my seedlings have matured! –  winwaed Jun 11 '11 at 0:46

Sprouting your seeds is a good way to tell whether they're going to germinate. Here's how I did it this year:

  1. Get some 1 quart sandwich bags, your old seeds, a magic marker and paper towel.
  2. Fold a paper towel so it'll fit inside the quart bag.
  3. Unfold the paper towel and draw four lines on it.
  4. Dampen the paper towel a little bit.
  5. Put 10 seeds in on the line you drew and fold the paper towel back over the seeds
  6. put the paper towel in the quart bag (keep flat)
  7. Put the quart bag carefully on a hottish spot (like on top of your hot water heater)

When the seeds sprout, you'll have a good notion of the ratio of sprouting vs non sprouting. (this probably won't work for leeks and other things that take forever to germinate)

(I read this somewhere, I'll post a source if I can remember)

As for the efficacy of the seeds, some say they're less disease resistant. But that's all I can say about it. It's probably like the difference in heavy metals when eating 2 month old talapia vs eating 26 year old walleye.

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