Hank Parker wrote, "We figure, w/o measuring, that a maple needs to be 30 to
40 years old to get to the 10-12" dba to tap."
Hank,
It is American tradition (tradition!) to not tap a maple tree until it
is 10" dba (dba means diameter at breast height). Continuing, another
tap-hole is drilled for every additional 5" dba.
The Quebecois that I had the opportunity to speak with told me that
they, and everyone they know who taps maple trees, begin tapping when the
tree measures 6" dba adding another tap-hole for each additional 6" dba.
Quebec produces 2/3 of the World's maple syrup.
Curiously, for a 30" dba tree, both methods have the same number of
taps.
Regarding the idea of tap-holes harming the trees, I have had weed
trees, maple trees that were in the way and needed to be culled. Rather
than to simply cut down 2" and 3" trees, I figured I'd put several taps in
each, drilling all the way through to the other side to extract their sap
before cutting them down. Apparently I got busy and failed to cut them down
as planned. When Summer came, I learned that, not only did I not kill the
trees but they seemed unaffected! So to learn from the experience, I let
them grow and tapped them similarly the following Spring. By the next
Summer, I learned that my plan to kill them by draining their sap wasn't
working.