Might want to check the ambient temperature pattern for your area for temperatures below ground. Root cellars need to be cool (not an expert but I think the cooler the better as long as it stays above freezing).
I grew up in SE PA and the house in which we lived had a ground floor built into a hillside, half was below ground, the other half not. We called this the basement as we had two living floors and an attic above it. The root cellar was dug below this basement so that it was 15-20 feet below ground at its deepest. It was dark, damp and full of spiders and I was scared to death to go down there. My mom stored her home made wine there.
This house was built in 1840 or so and was on a farm. The house I live in now has a full basement about 6-8 feet below ground and no root cellar. It was built in 1882 and is in town.
The farmhouse basement was cool enough, even in summer, that the bottles of Coke Cola stored there were a cool treat on a hot summer afternoon.
The present basement is where I keep my collection of tools and my sanity.
Andy
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In a crisis one does not rise to one's level of expectations but rather falls to one's level of training.