By now, I can safely assume that any of the various old seed that were sown late last February that have not yet germinated are not likely to do so. They were all so old that I knew at the time that their viability was questionable. Nonetheless, I could not discard them without confirming that they were no longer viable. Four months later, this empty flat just about confirms it.
So far, the sole survivor is a seedling of a California fan palm, Washingtonia filifera. It looks silly all alone in the otherwise empty flat. Yet, even if no other seedlings germinate, the effort will have been worth this dinky palm seedling. California fan palm happens to be my favorite palm; but I would have been just as pleased with something that is not a favorite.
This little seedling is still too young to be pulled and canned. It will therefore wait and grow in the flat for now, and perhaps until autumn. I still hope that other seed will germinate during that time. Even if they do not, the empty flat will get set aside where it will continue to be irrigated as needed until late next spring. Viable but old seed may be unusually slow to germinate.
I can not help but wonder if some of the seed did not get enough chill after they were sown late in February. Maple, ash, elm, birch and arborvitae might require more of a chill through more of winter to be convinced that the warm weather afterward really is spring. I am not quite ready to give up on them yet.
There are still many more very old seed to sow this autumn. For most, I do not expect germination to be any better than it was for this previous batch.
Tony Tomeo 
I just found some old seeds and threw them in a pot. I feel you have to give them a try.
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Exactly! It is not fair to just discard them.
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Knowing your expertise, I’m a little hesitant to ask this, but have you considered popping them in the fridge or freezer for a bit to get them the extended chill they require? As a lark, we planted blueberry seeds from some that we’d harvested, frozen, and forgotten for a few years, and I was quite surprised at how many germinated. Abe
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Yes, I did consider doing so; but I was hoping that they would get enough chill from being outside through the remainder of winter. We chilled some edelweiss seed, just because they want more of a chill than they can get here. They all germinated, but then promptly rotted off. About half of the old seed in the flat int he picture are palms seed that need no chill.
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That is one determined little palm. I have never heard the word canned for potting up. I think that is what it means? I like it.
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Well, I still talk like a nurseryman.
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I spotted it right away, looking like a blade of grass. Tough little plant. I hope it does well.
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It is easy enough to grow as a seedling. The difficulty will be finding a home for it later. It prefers to be in a warm and dry climate, and is normally planted in groups, rather than singly. I can worry about that later.
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