Definitely old growth.

First, measure up four-and-a-half feet, which is where you measure DBH (Diameter at Breast Height).

Mark it with a piece of tape, and then start measuring.

Keep measuring.

When you run out of measuring tape (in this case at 120 inches, or 10 feet), mark the spot. Then measure from that point to your starting point.

In this case we had 120 inches, plus 26 inches, which when added together equals 146 inches, which is almost 12 feet. That’s the circumference. Now, to find the diameter we divide by Pi. So, 146/3.14= 46.5 inches, which I am rounding up to 47 inches. That’s the diameter.

Now, to estimate the age of the tree, you need to know what kind of tree you are measuring and then use some kind of Growth Factor chart. See the previous post. (You can download a Step-By-Step Guide, which includes several charts.)

This tree I know as an old friend and as a burr oak. And, when I look at the charts, it appears to be off the chart. More than 152 years then, and probably in the 160 to 180 range. This tree, it would appear, was seedling sometime before the civil war, sometime before Wisconsin became a state, and back when Wiitewater was a campsite.