Have you ever heard that you can tell how old a tree was by counting the rings on its stump? The bummer about this method is the tree has to die before you can tell how old it is! Turns out, there is a way to estimate tree age while the tree is still alive.

Keep in mind, this method provides an estimate. This means the number you discover may not be the exact answer for how old the tree is, but it does get pretty close!

Today, you will get to learn how to estimate tree age, try it out in real life, and practice your measuring and multiplication skills at the same time.

Before you do this on your own, let’s practice.

The first thing you will do is find the

**diameter**(in inches) of your tree. Remember, you find diameter by dividing

**circumference**by

**pi**, or 3.14. So really, the first measurement you must make is the circumference of the tree. Since we’re not outside yet, let’s just try an example.

As a reminder, the circumference is the distance

**around**a circle.

The circumference of your tree is 52 inches.

**Finding diameter:**

Circumference / pi = Diameter

52 in / 3.14 = 16.56 in

Now that you have your diameter, you will multiply that number by the growth factor.

Click the link below to find the growth factor chart. The reason we need the growth factor chart is because not all trees grow at the same rate. This chart will help you find a more accurate estimation of the tree’s age based on the type of tree and it’s growth factor.

**Growth factor equation:**

Diameter x Growth factor = Tree age

16.56 in x 3 = 49.59

Based on the equations, the tree I measured is almost 50 years old!

Before you go outside and start measuring, choose three other trees on the Growth Factor Chart and practice the equations that we just did.

Now you are actually going to go outside and start measuring. Of course, not all of us are tree experts! If you are unsure about how to identify different types of trees, check out the link below to help you out.

- Trees
- Measuring tape
- Growth factor chart
- Pen
- Paper

- Print out the growth factor chart.
- Bring the chart and measuring tape outside with you.
- Find a tree that you want to measure.
- Identify the type of tree. If you are unsure, make your best guess! Remember, you can always go back and check your handbook.
- Before measuring, predict how old you think this tree is.
- Wrap the measuring tape around the trunk of the tree. Make sure it is pulled tight so your measurement is accurate.
- Write down your measurement (circumference) and then find the diameter of your tree using the equation from the example.
- Next, find the type of tree on the Growth Factor Chart to determine the growth factor for your tree.
- Use the Growth Factor equation from the example to determine the age of your tree.
- Compare your predictions with your findings. Were you close? As you continue measuring trees, are your predictions closer to your actual findings?

Extension: Plot a map of the trees in your area and create a legend for how old the trees are. You could color code the trees based on their ages. You might find that some areas have significantly older trees or some areas that have mostly younger trees. After completing the map, analyze why some areas would have older trees than others.

References:

http://www.education.com/activity/article/How_Old_Are_They/

http://mdc.mo.gov/your-property/your-trees-and-woods/backyard-tree-care/how-old-tree