The steel should outlast the wood in this case.
I would dig the hole at least 12" below the frost line in this case and make it bell shaped at the bottom. No need to go crazy on the width as 8" wide should be more than enough. Its not carrying any real weight in this application.
I would dig the hole at least 12" below the frost line in this case and make it bell shaped at the bottom. No need to go crazy on the width as 8" wide should be more than enough. Its not carrying any real weight in this application.