# How well does the radius of a tree correlate with its age?

I'm looking for a cheap non-invasive ways to approximate the age of a tree (a birch). Measuring the radius pops up in the mind as the first alternative. How would one do that? Measure at multiple defined heights?

I'm hoping that I could get some kind of confidence interval for the approximation, so that the data could be used in a scientific publication.

Or is there any reliable DIY radiocarbon dating technique?

• I'd take a look here: arborilogical.com/tree-articles/how-to-age-a-tree – CKM Feb 12 '15 at 23:21
• It's going to depend very strongly on species. I have some cottonwoods which I know were planted in the mid-60s, and which are about 4 feet thick at the base. (Some of the annual growth rings are almost an inch wide.) OTOH, some of the mountain mahogany I have for firewood is much older, yet only around 6 inches thick. – jamesqf Feb 12 '15 at 23:27
• Radiocarbon dating won't work. For a start the tree needs to be dead, which since you're not using the rings I'm assuming it isn't. Also the atomic testing in the 20th century completely messed up the level of C14 in the atmosphere, so radiocarbon dating can't be used for anything that didn't die 70 years ago or more. – Rob Mackinnon Feb 17 '15 at 16:43
• @RobMackinnon But it looks like the C-14 from bombs has been utilized in other tests. And as far as OP's original question goes, C-14 dating would not be a cheap way to do it, and you couldn't do it yourself. The uncertainty in the measurements also means that C-14 is only good for approximate age, and may be off by around 100 years, which is a lot compared to the lifespan of most trees. Dating based on bomb carbon might actually be better for recent objects. – user137 Feb 22 '15 at 17:08