As kids, Santa always left us a nice large shiny red delicious apple, a big navel orange and walnuts in our stockings. Santa apparently left my wife’s grandmother the same things (well, definitely the walnuts, and I think the rest too) many years ago, several hours away (in a remote rural area). All of this in the mid-Atlantic…
Any ideas what this represents, and where this tradition got started? Is it widespread?
It’s possible that in times past, these things were seen as treats and therefore appropriate for the stockings. I remember reading in the Little House series about Laura and her sisters getting oranges in their stockings at one point and how excited they were about them.
Just a WAG.
IIRC, since transcontintental shipping was not what it is today, oranges, shipped from Florida, California or god knows where, where a special treat available only at substantial expense. And it would have been an extra-special treat to eat any type of fresh fruit in December (everything else would have been caned at least in Little House days).
The two preceding replies are good guesses, and here’s my WAG to go on top of them.
It’s possible that the tradition also has much older overtones, and may be a way of celebrating the recent harvest.
My Polish grandparents in NJ have always done the walnuts in the stockings. No clue why. No one ever had a nut cracker around either. 
Lately they’ve been doing Clementines, which are appreciated much more and rather easier to eat.
canned, that is. ::duh::