I'm interested in estimating the age of some live trees. I've found this
link: http://www.learner.org/jnorth/tm/leaf/HowOld.html, which gives a
"growth factor" for several species but is not comprehensive.

White Pine (Pinus strobus) and Eastern Redcedar (Juniperus virginianus) are
two species for which I would like to find a "growth factor".