www.ancienttreeforum.org.uk says: "Ancient trees are those which have reached a great age in comparison with others of the same species." "A birch tree could be

www.ancienttreeforum.org.uk says: "Ancient trees are those which have reached a great age in comparison with others of the same species." "A birch tree could be considered as ancient at 150 years old, for example, but an oak tree would not be thought of as ancient until it’s at least 400 years old." I'm not sure everyone would understand the expression in that way, though. (As already discussed in the Wikipedia talk page, now that this tree has been felled, someone should count the rings and tell us exactly how old it was!)