Age Is Just a Number… Of Tree Rings

How old is this tree? How long will it live? These questions are difficult to answer, as many factors contribute to tree size and age. The only way to know the exact age of a tree is to cut it down and count the rings within the stump, or collect a sample of the trunk with an increment borer. Trees in temperate climates put on denser wood cells in the fall to prepare for winter, leaving a “ring” of darker colored wood that is visible when the tree is cut. The darker rings can be counted as one year of growth. Another method to get a tree age estimate is to find records of when the tree was planted. Trees are often planted in the urban landscape at the time that houses are built. Aerial imagery can also assist with tracking the size or presence of a tree. Research in forestry has led to the creation of tree age charts estimated by trunk size which you can find online. Tree species, health and maturity can greatly influence trees growth rate, so using these charts will provide a good estimate, though not an exact age.
Tree age is important to prescribing the best tree care. Young trees are much more adaptable to changes in their environment, so they can handle higher pruning doses and recover from moderate pest issues more quickly. Mature trees are less adaptable and need a lighter pruning dose and more timely intervention if a pest issue arises or damages occur. Crown growth slows significantly in mature trees as they reach “over mature” and then “veteran” status (age varies greatly by species). Pruning mature trees should focus on removing deadwood and only pruning live growth when necessary. These trees require close monitoring, and ample root zone protection if construction is to occur nearby.
As far as tree longevity, it all comes down to tree health. Many of our native oak trees can live for 200-400+ years in the natural forest. However, it is uncommon to find these over mature oaks in the urban forest. Street trees specifically have a remarkably short life span, with a small percentage reaching 40 years of age. Urban trees, and particularly street trees, are subject to much harsher conditions than trees in a natural forest setting. One crucial difference? Soil health. The challenges of urban growing spaces are why we as arborists must evaluate and care for trees within our urban forest. If you are looking to help your trees thrive, contact your Wachtel Tree Science Certified Arborist to give you the correct care for your trees depending on species and age.

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