Where I grew up (41.3 deg N, on the Atlantic coast) I was always amazed by our neighbor, who would bury his ~15 foot tall fig tree every year to protect it from freezing. For some reason in my child mind it seemed to defy the laws of nature, though of course it was quite the opposite!
When I lived in Toronto, my next door neighbour Luigi did that with a fig tree he had brought with him from his native Sicily some decades ago. Every year it bore a couple dozen figs for him. The whole family was a living stereotype in pretty much every way, but his gardening technique definitely bore fruit.
Where I live in Eastern Europe (44°26′7″), we have acclimatized fig trees. And we have temperatures as low as -20C or even -25C (-4 and -13 Fahrenheit).
My parents who still live in the same house do have a small fig tree they don't bury, and my mother's parents a hundred miles south had a larger one in their backyard. I don't know if burying fig trees in that climate is necessary to be honest, maybe it was just a practice my neighbor brought with him (he was Italian as well).
