Roger, I’m just thinking of other fruits. The seed from said fruit (assuming it’s not a hybrid like an interspecific with the other species conferring cold hardiness genes) usually is only as hardy as the parent species.
If so, then that Hachiya seed probably needs the same growing conditions as the tree itself. It needs a zone 7 or 8 winter. I put loads of kumquat, loquat seed and trifoliate orange seed outside. They usually don’t ever germinate because my winters are at least one zone too cold (on a very very rare occasion they sometimes do). I assume kakis are no different.
Did you cut any of the seeds open to look for the “spoon”, “knife”, or “fork” to see what your winter weather prediction will be?
I haven’t cut any open like that but what I did do was roast a dozen in a pan for 20 minutes, ground them in my coffee grinder and brewed them. I saw a guy use them this way on a YouTube video and he lived to post the video so I assumed it would be safe to try. Well, it didn’t taste like coffee, it tasted like a black tea with a nutty finish. I’m going to oven roast them for much longer and see if that makes them more coffee-like. We’ve gotta come up with something before the coffee plant goes extinct.