I have a beautiful old oak tree in my back yard (mid-atlantic area)
with a circumference of about 13 feet.
Lately, it seems to be less productive. ie in the fall, it doesn't
drop as many leaves as it used to and in the
spring, it takes longer to reach full bloom than any other similar oak
in the area.

As I'm not prepared to take a core sample, I don't know how far apart
the annual rings are so I can only
make a rough guess as to its age. I'm assuming it's 130-200 years old,
Can anyone verify that number?

Is it's slowness to regenerate a sign of age? stress? or irrelevant?

Thanks