I've grown old seeds of a variety, meaning 10 plus years old, but never fresh seeds of that same variety at the same time.

The reason I'd be growing the old ones is b'c I needed to do seed production b'c I didn't have any fresh ones or had few of them, or b'c someone was looking for seeds of a variety no longer available commercially or currently being listed in the SSE YEarbook. And more recently I've had to do that for a couple of persons who have found that some OP varieties have gone south and are no longer what they should be.

let me amend that last sentence to say that I now send those old seeds to the person(s) requesting them b'c I no longer can germinate and transplant and raise plants myself.

I noticed another thread here where you were saying that you deal with seeds and selling to others so I suppose your question pertains more to your bulk seed purchases, repacking and selling those seeds as you described, rather than concerns about your own seeds that you would use for home growing. Right?

Carolyn

Carolyne, all the bulk seeds I have that I am repackaging some of I bought last year and know they are good because the ones from the same package I am planting for the plants I intend to use for myself or sell are already starting to sprout after only four days from the day I planted them. The old seeds I have I am not selling, in fact I only have less than a regular retail package of each left. I know I planted some last year when they were 8 years old and they sprouted and produced tomatoes, but I don't know if fresh seed would have produced better plants.
I notice the Matina I planted from now 9 year old seeds still haven't sprouted after five days. The ones I planted last year from then 8 year old seeds were the first to produce tomatoes even though they were slow to sprout too.

If not talking about paired seed sowing of the same variety, one batch old, another batch fresh, then I can perhaps make a few comments.

Seed germination does decrease with age, especially that of heart varieties, but I expect and get germination of maybe 60-70% for seeds up to about 5 yo stored only at ambient temps and humidity.

From about 5 to 12 years old of course germination takes much longer but I've never had seedlings that were any less robust than those one would get with fresh seed.

When it gets beyond maybe 12 yo then I would soak the seeds in a brew and then double sow. And those might take weeks to a month or two to germinate, but again the seedlings are fine.

Getting close to 20 yo seed do the soak for longer, double sow and pray. LOL For several varieties it's taken several months before any seed germination at all and sometimes nothing.

The bigggest enemy of older seeds is dehydration, so I think that issue needs to be faced before any other methods are even mentioned.

Carolyn

Carolyn, do you think vacuum packing the seeds when still fresh would prevent moisture loss? I am thinking of the seed I am just getting now. I could put my foodsaver to work, lol. Either by putting them all in a plastic container and then vacuum sealing it, or by vacuum sealing each package of seed in plastic individually. Could it harm the seed?

I would never have thought to keep seeds for more than a few weeks trying to germinate them. If you have had seed germinate after several months how long do you keep trying before giving up and tossing them out?

Margaret Roach on Facebook (Martha Stewart horticulturist) posted photos of a dramatic difference between plants grown from fresh seed vs. same plants from slightly older seeds.

I'm with Caroline on this one. The only difference I have ever perceived is time to germinate. If Margaret Roach saw dramatic differences I would have to question source of seeds being from the same strain without a possible cross between years or possibly some carryover of a disease on the older seed.

I'm a believer in storing my seeds in the freezer. Many many years ago that was not my practice. Then an elderly lady
in Kentucky who grew a marvelous tomato garden suggested
I do so, and gave me a few other suggestions regarding seed saving, all of which I took to heart. I soon began to see results in terms of faster germination, sustained seed viability,
and I feel an overall better result in the garden. The latter
opinion is just that and would be very difficult to quantify or prove. But, at any rate, I'm convinced seed saving techniques
and storage methods have a large impact on seed viability
and may have some impact on plant performance.

I have experienced more crosses over the years than I ever imagined possible, have actually lost some good varieties that way. There is another possible reason for dramatic difference in performance.

Inside the seed there is very little substance. A little bit of a plant (embryo), and mostly endosperm. The endosperm serves no function beyond germination, so, if the seed germinates, then the endosperm will have no effect on plant vigor beyond that whether it be a 10 week or 10 year old seed.

Other then environment, the only determining factor in plant vigor would be genetics. During dormancy, genetic material is somewhat damaged, however, within cells there are enzymes which actually repair damaged DNA! In a seed cell, all functions, including enzymatic activity are held in a (nearly) suspended animation until seed dormancy is broken. One of the first things that happens is the enzymes go to work repairing the genetic material. If the DNA is so damaged that the cell can not repair it, it goes into cell suicide (apoptosis, programmed cell death). If enough of the genetic material is irreparable, we would not see any germination. If the damage is reparable, then normal cell life continues, assuming favorable growing conditions. I think, overall, aside from germination rate, seed age will not have any significant effect on overall plant health and/or vigor.

I just germinated 2006 seeds which were partially eaten by some mice I assume as friend who gave them to me at my request, told me. They went as gangbusters and plenty of life in those seeds that did not get destroyed.
Seed that takes forever to germinate has something lacking in it to function properly so out of entire batch you might get one or two plants that will be robust but rest will need lots of TLC. Since lots depends on care seedling receive I think you still can have nice harvest, just might need more work or will have to cull more seedlings to leave your with most lively one.