Q: I am trying to find out the age of several live oak trees at my father-in-law’s house in north Florida. Is there some general way to determine their age based on their diameter?
A: According to Certified Arborist Brian Arnold (678-432-6892), determining the age of the oaks through non-invasive observation would be almost impossible. The diameter of the trunk is influenced by many factors, including soil conditions, rainfall and sun exposure. The trunk of a hundred year old tree growing in a good spot might be twice the size of an equally aged tree growing in poor conditions.
It is possible to count tree rings using a tool called an increment borer. The tool bores a hole in the tree trunk and removes a slender core of tissue reaching the center of the trunk. Brian advises against the borer tool because the hole can give insects and diseases access to the trunk interior.
Maybe your best bet is to try contacting previous owners of the house to ask about their earliest memories of the trees.