[thysultan]

Buy seeds, and seal them with little sprinkles of wisdom like fortune cookies in places that would be accessible in the aftermath, the new inheritors of the earth will regard you as a prophet or god when they re-learn the ancient art of farming.

[exporectomy]

I think it's a bit fanciful to believe that post-apocalyptic people would have any interest in studying or learning from the past. Archeology is a very recent invention. Mostly, people just looted whatever old things they found for their immediate use or destroyed them because they didn't matter. The world will be awash in old crap by then too or if it isn't, the time capsules you leave will be just as gone as everything else.

[Syonyk]

Unfortunately, outside some particular environmental conditions that are far from trivial to reproduce most places, seeds don't last indefinitely. The gemination rate tends to drop off fairly rapidly as a factor of years.

They're designed to survive from late summer to spring, not years or the decades that would be needed for that sort of thing.

Now, there's a ton you can do with seeds - work on optimizing various heirloom varieties of plants to your local climate (as opposed to the "one seed for all places, apply energy to the field until they behave!" approach that is widely used today), and trying to keep some genetic diversity in the seeds you use, but I don't think "random seed capsules" are likely to work over the likely timeframes involved.