you want eastern red cedar, western doesn't share the same properties and will not last as long. Eastern is more aromatic (repels more bugs)

Black locust makes a darn good post wood similar to Osage orange and should last 20+ years. Honey locust is about half as good (10-12 years). These all work well in water

Mat Peirce
1.25 acre southeast Iowa pond
LMB, BG, YP, WE, HSB, RES, BCP