Sheldon wrote:

Never install any wooden pole/post in concrete... it will heave and it
will rot. Set in gravel or sand or any material contribuing to good
drainage, then back fill with whatever soil was removed. Only metal
posts/poles get set into concrete, and even those should have good
drainage material at the bottom or they will heave. If your frost
penetration is 8' than you need to go at least that depth, especially
with wood.

What part does the frost line play?
I always thought the depts was determined by the leverage applied by
the pole.
What am I missing?