The biggest white oak I know of in Bethesda, Md.—16 feet in circumference at breast height, maybe 100 feet tall—is a five-minute stroll from my house. I found it one evening on a walk. Just off a 50-yard stretch of paved walking path between two streets. There was a single spotlight pointing up the trunk.

It didn’t look all that big at first. Definitely a honker, but nothing exceptional. At first. But it gained mass with every step I took toward it. It was leaning away from me. When I got to it, the amount of wood locked up in that tree stunned me. There had to be an acre’s worth of oak flooring. I looked up at a nearly horizontal first branch 35 feet up. If that thing fell—and, like the tree, its weight and size kept growing—it would take out several houses. How could the trunk possibly support however many tons that branch weighed?

Something shifted and the tree was no longer just another tree. It was the tree, a king tree. It was more than 2½ arm spans around, 16 feet. White oaks in the gentler USDA plant-hardiness zones 3b to 8b can live 600 years. Say this one was a baby, just 400 years. A sapling when the first ship landed at Jamestown. Old growth, a primeval tree.

“Oleh,” I said, echoing the greeting that Faulkner’s Sam Fathers—a Chickasaw chief in whom the blood of slaves had flowed for two generations—reserved for ancient things. “Grandfather.”

I stepped back. The tree became even more timeless. This was how giant white oaks have looked for however long they’ve been around. Was that 5 million years, 20 million, 100 million? I had no idea.

Back home, I’d realized I’d long ago forgotten the formula to calculate diameter from circumference, so I found it online. Diameter is the circumference divided by pi, or a smidge over 5 feet. A tree that had been living long before I had, one I hoped would be living long after I was gone. Oleh, I said to myself. Grandfather.