We offer either Joinery Redwood posts planed Smooth to match the gates, but only to be used when fixing to a wall and not concreted in.
We use posts from an old family sawmill where quality of the timber sourced is paramount.
They saw timbers traditionally used in fencing/gate applications which will outlast a “wrong spec timber” which is pressure treated.
Most pressure treated timber posts would be unfit to put in the ground if not pressure treated.
Pressure treatment does not mean they will last longer than a timber species that is naturally resilient to ROT.