An entire fortress's worth of seeds takes up only a few bags.
Mine would only take up one or two if the dwarves would stop starting new bags just because they can. 8^(
Of course, that would potentially lead to the inverse problem mentioned by another reply about cancellation spam due to all the seeds being in too few bags, but I don't think it'd be as big a deal once I have space cleared out for farms.
I have this bad habit of starting off all my forts as hunter-gatherer villages: hunt and gather plants for food and drink, make bolts for more hunting from the bones of the slain wild beasts, lather rinse repeat while I set up components of the long-term fortress one at a time. I also have a bad habit of wanting to avoid wasting things like seeds even if I haven't set up the farms yet... maybe I just need to change my attitude. 8^\
That said, if seeds don't rot even if forbidden (whether in a stockpile, which can be arranged, or not, which doesn't even involve arranging then), then I suppose it's entirely doable (even if not quite as simple/automatic) to just dump them all and get them back when I go set up the farms -- that would be more or less the sort of solution I'm looking for, even if not as clean and automatic as stockpile settings that wouldn't involve dumping and later unforbidding.
And that said, if Larix is right that seeds in a workshop won't be bagged (and won't rot there either), that would be an excellent alternative with less manual dump-designating... I'm gonna try that one and report back.
...And if that fails I guess I'll just dump the seeds, leave them forbidden and make a note if they rot (though it sounds like they won't). Thanks for the ideas, everyone!
[ninja'd]
Dwarves are a bit stupid and take the container to a single seed instead of the other way around.
Why did they start doing this btw? IIRC, they used to carry items to containers sensibly, and then it changed in 2012, right?
I think the idea is that they don't have to make as many trips if they carry the bag and make a sweep of a room full of seeds. But for some reason the job system isn't worked out to expect that and not try to create lots of jobs with lots of cancellation spam. And I'm not sure if they can plant more than one seed like how they pick up more than one seed in a single bag-trip. And I'm not sure that they always go deal with all the seeds they could/ought, many times -- I've seen them grab three seeds when there are ten lying around. In short... the idea is right when you think of it in terms of "doing a job with multiple seeds and one bag", but the execution needs more tweaking to actually gain efficiency in many cases.