Here is Missouri we use "hedge", also known as Osage Orange. The Maclura Pomifera tree is highly insect and decay resistant; very heavy and dense.
It was widely distributed during the dust bowl days and planted as windbreaks. I would say the majority of farms here in the Midwest use this along with metal T posts, mainly because of its local availability.
Hedge posts can often be found for sale in the rural areas, or found at farm auctions. I have no clue if you have this species or similar in your area, but if you do - you can't go wrong.
Here is what the non edible fruit looks like. If I had a nickel for everyone of those I tossed into the sky and shot with a shotgun...
FWIW, the scrub cedar we have here isn't worth diddly for posts. For that matter, neither is the pine.
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