Holly trees may be pruned to grow as a hedge, but at full maturity they will grow as high as 50 feet, spreading as much as 40 feet near the base. The tree grows in a pyramidal shape. Evergreen holly trees are used in holiday decoration, but they also make attractive landscaping trees. Measure the age of the tree without cutting it down.
Measure 4 1/2 feet from the ground up the trunk of the tree using a tape measure. Mark the spot with your hand or draw a small line with a piece of chalk.
Circle the tape measure around the trunk of the tree at the mark you made, measuring the circumference of the trunk. Write down the measurement.
Multiply each foot by 12, and add that figure to any remaining inches from the measurement you took. This yields the circumference of the tree in inches.
Multiply the resulting number by 2.54 to determine the circumference of the tree in centimetres.
Divide the centimetre circumference by 1.25, the average annual growth rate of holly trees annually. The resulting figure gives you an estimate of the tree's actual age. The number isn't exact, but it will give you a good estimate of about how old your holly tree is, without damaging any part of the tree itself.
Use a tree borer to get a more accurate reading on the age of a holly tree. Tree borers are inserted into the trunk so a small section may be pulled out; with this, you can simply count the rings to find the tree's age. Tree borers will damage your tree, however, so they are not advisable unless you have a truly pressing need to get an accurate age for your tree.