This question is a great one! You might be asking this question because you have an oak in your yard or elsewhere on your property that has been there longer than anyone can remember, and you would love to know its age.

Or you have heard tales of how old some southern USA oak trees have gotten. Either way, it is a worthy question to ask and a fun project if you have a few minutes, a long tape measure, and a calculator.

So the answer to this question about how old oak trees get will be interesting but might not help you as much as the answer to the question: how can you tell how old an oak tree is? This calculation is essential if you are trying to calculate an estimated age of an oak tree on your property.

Well, great news! This article will answer both of those questions. You just might have to do a little math along the way.

How Old?

The answer to how old oak trees can get may surprise you. Scientists have estimated that several famous oak trees are over 1,000 years old! The legendary Angel Oak near Johns Island, South Carolina, is estimated to be nearly 1,500 years old. Check out this article for some of those other famous oak trees across the southern USA.

It is remarkable to consider how many generations of your ancestors lived and died while those trees have been alive. They are indeed a gift to be treasured. Many are breathtakingly large with complex systems of branches and trees. Some of the most iconic are decorated by Spanish moss.

Those trees that live over 1,000 years tend to be remarkable and exceptional indeed. Scientists say that 1,000 years is the topmost lifespan for an oak tree. There are a host of factors that can cause trees to die out much younger than that age as well, including what type of oak tree it is and where it is growing. More details on that below.

But just so you know, oak tree ages are estimated, because unless you were there when it first sprouted from an acorn, the most reliable method for determining its age is counting its rings. The only problem is that you can’t reliably do so until after the tree has died. Oak trees produce a ring for every year it lives. But you certainly don’t want to cut down a tree to see how long it has been alive!

It is possible to take a core from a live tree with a borer to determine its age, but to do so can introduce damage or disease to the tree if the procedure is not done correctly. So another method should be used to determine how old it is.

Calculate the Age of Your Oak Tree

These four steps will guide you on how to calculate a rough estimate of the age of your tree without injuring it in any way.

  1. Measure its circumference. Use a measuring tape. Pick a spot that is approximately 4.5 feet from the ground to measure. This spot is a standard measurement spot for arborists. Your results will be accurate if you measure at this height.
  2. Convert your measurement into inches. So, multiply every foot by 12 inches and then add the remaining inches for your total number of inches.
  3. Calculate the diameter of your tree. Divide the number of inches you determined to be the diameter of your tree and divide by 3.14 (that wonder constant people call pi). This number will be the diameter of your tree.
  4. Multiply the diameter by the growth factor for your species of oak. This calculation is essential to get correct because of the variety of growth rates for different trees. See the growth rates noted below.

Species Tree Growth Factor

White Oak 5

Red Oak 4

Pin Oak 3

If you don’t know the species of your tree, you can get an estimate by multiplying the diameter by 3, 4, and 5. You can reasonably guess that the age of your oak will fall within that range. In fact, many people advise the best estimate is to multiply by 4 — right in the middle of those numbers.

If you want to know exactly what kind of tree you have, you will need to look closely at the leaf types for the best opportunity to identify which oak you have. You might also check this list of common oak types, which includes the following.

Types of White Oak Trees

  • Chinkapin
  • Post Oak
  • Bur Oak
  • White Oak

Types of Red Oak Trees

  • Willow Oak
  • Black Oak
  • Japanese Evergreen Oak
  • Water Oak
  • Pin Oak

One Note About Calculating Age

The truth is that a growth factor assumes even growth year after year, but as is widely known, life is usually more about hills and valleys than steady, consistent living. According to rainfall and sun from year to year and location of the tree, there can be a wide variety of growth from year to year.

Trees in more populated areas grow differently than those in the woodland areas. Urban dwelling trees grow more slowly because of the stress that comes with living in the city: traffic, heat from the concrete, and stress on its roots. So tree growth rates will need to be adjusted slightly because they grow slower in urban areas. Many suggest that there is as much as a 25% difference in urban growth rates over time.

Unfortunately, growth in an urban area can also shorten the life of a tree. Some calculate they may live for half the number of years as a tree might in a field free from competition.

Fun Facts About Oaks

  • Oakwood is so dense and heavy that it was used to make battleships. The USS Constitution was called “Old Ironsides” in the War of 1812, not because it was made of iron. In fact, it was a live oak hull so dense that cannonballs fired from British warships bounced off of it!
  • Acorns are produced by the thousands every fall by mature oak trees. Acorns are feasted on by squirrels and also by pigs, bears, and deer.
  • The name “live oak” was attributed to oak trees because oaks are green every day of the year.
  • Oaks provide homes to birds, squirrels, and Spanish moss.
  • A mature oak can drink more than 50 gallons of water per day through its deep roots.
  • Live oaks can stand up to 100 feet tall.
  • The crowns of the most enormous live oaks reach diameters of 150 feet across.

History Fun

  • The Friendship Oak of Long Beach, Mississippi, is over 500 years old and has survived numerous hurricanes over the years.
  • The Seven Sisters Oak of Louisburg, Louisiana, is another oak estimate to be more than 1,000 years old. How big is its circumference? Over 37 feet!
  • The Cellon Oak of Alachua, Florida, is so big that it can be seen from space.
  • The Dueling Oaks of New Orleans, Louisiana, were famous for the duels that took place under them. Just as dueling has become a thing of the past, one of these renowned oak trees was toppled during a hurricane, but the other remains and is growing stronger every year.
Author

I have a bachelor's degree in construction engineering. When I’m not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies...I’m at home with my wife, two daughters and a dog. Outside of family, I love grilling and barbequing on my Big Green Egg and working on projects around the house.

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