While this source ( Mother Earth News(r) ) is not my first choice on prepper information, this article contains some good information, sans advertising, about in-ground winter food storage:
http://www.motherearthnews.com/diy/garden-yard/root-cellars-zm0z11zkonDo note that this method would also work for making live food caches. You might cache a crop of root vegies in an out-of-the-way spot and cover it with leaves and branches as camouflage. DO NOT try this with store bought vegies as they are not likely to survive being re-buried after exposure while transported to stores. Freshly harvested root crops are best for this method.
The storage time for live crops is limited to only a few winter months, but if you lack indoor storage space or refrigeration, this could save your food stores...