Counting old-growth tree rings

A healthy Ponderosa Pine blew down this winter. We cut the log loose from its stump and saw some interesting ring patterns we hadn't noticed in other trees. There were long periods of drought when the tree was young, but no apparent fire damage. That puzzled us.


This tree had rings so tight at times it required a magnifier to count them.

We decided to count the rings. We fetched a magnifier, marker and push-pins, and started at the outermost ring.

When this tree was alive it was leaning, slightly bent, not very tall or large, probably of no commercial value -- that's what saved it from the saw over the decades, even when this canyon was last logged in the 1970s.

The tree turned out to be approximately 170 years old. That means it sprouted in about 1841. In that year Lieutenant Charles F. Wilkes led a U.S. Naval expedition of the Pacific Northwest. Oregon was not yet an organized territory. A group of pioneers led by John Bidwell set off on the Oregon Trail, sparking the Great Migration. The Homestead Act and the American Civil War were still 20 years away. WA became a state in 1889, when this tree was almost 50 years old.

This was an attractive tree, one that we left even though it shaded our solar array for an hour on winter days. It had the characteristic reddish bark found only on certain old PPs. Its slant and curve gave it a Bonsai look. It stood in the open, one of two pines on a minor ridge.

This relatively small Ponderosa Pine was about 170 years old. It sprouted before the Civil War.

Its rings tell a story of survival. It lived through at least two major droughts of a decade or longer -- one in the 1920s, when we believe a forest fire swept across this canyon. Embedded knots terminate about that time, perhaps burned off by a passing ground fire that otherwise spared this tree. The other major drought was in the 1950s.

When the stump dries out I want to cut a slab from it and get it over to our friend Dick S., who is an expert on forest fire ecology in our region. Maybe he can pinpoint the precise year of the fire.