I just received a first year chestnut seedling, about 7" tall. Is it better to winter it in garage? Or it is still ok to plant it outside?
Also, is it required to have cross pollination? I believe this is an Asian chestnut.
I need to read more on chestnut. 
I would plant in ground now , a well drained site.
Yes , need a pollinator.
My sister planted a Chinese chestnut around 40 years ago at my mom’s…it’s not got another within at least a mile…and bears annually, except this year when two freezes got both sets of flowers.
It’s only about 20 feet tall, too.
I put in 4 seedlings (hybrid chestnut) a couple years ago and yeah I did it in the fall in zone 5b.
I’ll ask my friend to see if they get any other tree to pollinate. I did not hear them stating that. Varieties could be different.
If you plant it now, I’d put up some good protection around it.