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

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

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?

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.

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.