The best method by which to tell the age of a pecan tree depends on exactly how precise you wish to be. The ideal method is to fell the tree and then count all the growth rings. Generally, this approach is probably a little too dramatic, and there are other alternatives that can give you a good approximate answer which we will investigate further here.
What You'll Learn Today
Can You Estimate The Age Of A Tree?
It’s possible to estimate the age of a tree without cutting it down in several ways:
- Circumference – By measuring around the tree’s trunk, you can get an approximate age.
- Diameter & Radius – A little more tricky, but there is a correlation between diameter and radius measurements with age.
- Core Sample – A tool called an “increment borer” can be used to take a core sample for analysis.
- Growth Factor – This is a number you can use in a mathematical equation along with various measurements to give you the tree’s age.
The easiest method to give a rough approximation of the tree’s age is to simply measure around the trunk at chest height using a soft inch tape, such as the kind used in dressmaking.
If you don’t have a soft tape, then you can use twine and mark off the measurement. Then use a metal tape to take the reading.
This circumference measurement in inches will give you a very rough approximation of the age of the tree.
The reason why this method isn’t very accurate is that different species of tree grow at different rates and have varying trunk sizes. This is also affected by the growing conditions of individual trees.
Diameter & Radius
To use the diameter or radius of a tree to tell its age, you will also need to know either the average ring width from a nearby stump of another pecan tree or the average growth rate for pecan trees which is approximately 18.5 inches per year.
1. Calculate the diameter of the tree. To do this, divide the circumference by pi 3.14.
2. Next, you’ll need to know the radius. To calculate this, divide the diameter number by 2.
3. You will need to make an allowance for the thickness of the bark. For mature pecan trees, this is approximately 1 inch. Subtract this from the radius measurement.
4. Now, you need to know the average ring width, which you can measure by looking at the space between the rings on any fallen or felled pecan trees located in the same area.
If the stump has a 25-inch radius with 125 rings, then the average ring width is 0.2 (1/5) of an inch.
If you can’t get a ring width measurement, use the average annual growth rate instead. For pecan trees, this is 18.5 inches per year.
5. You now need to divide the radius measurement (excluding bark) by the ring width. Or, if you’re using the growth rate to make your calculation divide the circumference (less two inches for bark) by the growth rate. Now you have the approximate age of your tree.
To use a core sample to tell the age of your tree, you will need a tool called an Increment Borer.
This rather resembles an auger and is T-shaped with an end piece that is shaped like an apple corer. There is a separate part called the extractor that fits inside the auger.
You will need to use an increment borer that is long enough to go through ¾ of the way through your tree at its widest point. To determine the perfect length calculate the diameter of the tree, divide by 4, and then multiply the answer by 3 to get the perfect measurement.
Increment borers can be found at forestry supply stores or online.
1. Start by standing by the tree and place the increment borer, without the extractor, against the middle of the trunk of the tree at breast height.
2. By turning the handle clockwise and applying firm pressure, screw the borer into the tree until you are two to three inches beyond the central point into the trunk of the tree. It is best to make a mark on the shaft of the borer with a marker pen before you start so you know how far you need to go and when to stop.
3. Insert the extractor section and start turning the handle in a counterclockwise direction. This will remove the borer and the sample from the tree.
4. On the core sample, you will see a series of curved lines, which are the rings of the tree.
5. Locate the pith (central point in the tree) and count the rings from that point back to the end before you reach the bark. The number of dark rings gives you the age of the tree, less five to 10 years.
To calculate the true approximate age, add 7.5 years to the number of rings you counted.
If you find it difficult to see the rings clearly, you can use 60-grit sandpaper to gently rub down the sample and make the rings more visible. You can also use a magnifying glass.
Professional arborists use a number called the “growth factor” to determine the age of a tree.
Here’s how to use it:
- Find the growth factor for the species of tree you are trying to age. For pecan trees, the growth factor is 4.5, as it is in the walnut family.
- Measure around the tree’s trunk at your breast height (between four or five feet from the ground) to give you the circumference. If the tree is on uneven ground, stand at the midway point between the high and the low level and take your measurement from there.
- Next, divide your circumference measurement by pi 3.14 to give you the diameter. This measurement is called the DBH (diameter at breast height).
- Multiply the growth factor, 4.5, by the DBH to give you the approximate age of the tree.
In this video, you can see how a tree is being aged using its growth factor and diameter:
Just like people, trees grow at slightly different rates. They will ultimately reach different heights, so any age you deduce will only ever be approximate.
Pecan trees that are grown in an open situation where they are not competing for light, moisture, and nutrients develop huge trunks and have an open oval canopy that will extend low down on the trunk.
In comparison, pecan trees that grow in a forest situation where trees are much closer together have taller, straight trunks, with compact, triangular canopies that are at the top of the tree.
What Is The Growth Factor Of A Pecan Tree?
Growth factors are determined by calculating a mean average from measurements taken from many different trees of the same species. The diameter measurement is divided by the tree’s actual age by counting the growth rings.
For pecan trees, the growth factor is 4.5 (walnut family) as it grows at a medium rate. Common Horsechestnut has a growth factor of 8 as they grow slowly, and Silver Maple has a growth factor of 3 as they grow more quickly.
Keep in mind that this is still only an approximate value, as the cultivar of pecan, location, and growing conditions of each individual tree can dramatically affect the way they grow.
For example, in fertile soil with good drainage, a plentiful water supply, and an open location, a pecan tree may reach 100 feet in height once fully grown.
If the growing conditions aren’t optimal, then a tree may only reach 70 to 80 feet. The speed at which they grow will also be affected, so the growth factor measurement can be skewed.
The diameter of a fully grown pecan tree’s trunk will usually reach around six feet and grow at a rate of 13 to 24 inches per year, taking 20 to 25 years to reach full maturity.
Do Pecan Trees Get Too Old To Produce?
Many pecan trees will follow a cycle known as “alternate bearing.” This is when the tree crops heavily one year and then far more lightly the following one.
As the trees grow old, especially if they are not cared for, their production rates will decrease. It is usual for all pecan trees to start declining in production by the time they reach 50 or 60 years of age, although, in optimum conditions, this could be delayed until the tree is much older.
If you plant a pecan tree in your garden and look after it well, it is likely to continue producing abundantly throughout your lifetime.
It isn’t unusual for pecans to live to be well over 100 years old, and in the right conditions, they can reach in excess of 300 years.
Do You Need More Than One Pecan Tree To Produce Nuts?
Pecan trees are monoecious, meaning they have male and female flowers on the same tree.
It would therefore be reasonable to think that a single tree would pollinate itself as several fruit trees do. Unfortunately, this isn’t the case, as the male and female flowers appear at different times, so the trees are not self-pollinating.
You will need at least two pecan trees of different varieties so that the coincidence of male flowers in one and female flowers in the other happen together.
Trees that shed pollen from their male catkins before they produce female flowers are called Type I pollinators.
Trees that produce female catkins before the male catkins start producing pollen are called Type II pollinators.
You need a type I and a type II for successful pollination and a good number of nuts to be produced.
The pollen is spread by wind and not by insects, so the proximity of the trees to each other needs to be relatively close.
Pecan trees start to bear fruit from the age of four to 12 years, depending on the cultivar and how the trees were grown.
Trees grown from nuts take the longest, and those grown from grafts take the shortest time to produce.
There are various ways to tell the age of a pecan tree or any other type of tree.
Remember that any calculated ages for trees will only ever be approximate. This is due to the different growth rates of individual trees due to cultivars and growing conditions.
For felled trees telling the age is rather simpler as it is just a case of counting the rings and adding 7.5 more to the years to give you a fairly accurate answer. This still only gives an approximate age and can be out by around 2.5 years either way.
You’ll find more articles about growing and caring for pecans on our website, along with articles to help you grow a wide variety of other fruit trees and much more besides.