Some trees or tree groups can survive for thousands of years. The oldest known individual tree, “The Sisters,” is located in Lebanon and has an estimated age of around 6,000 years. The oldest colony of trees, which may be as many as 130,000 years old, is an unnamed group of critically endangered King’s lomatia trees located in Tasmania.
Since many plants can outlive humans many times over, and we are always curious about the most extreme example of any phenomenon, it is no surprise that we are interested in quantifying which plant is the oldest and what the limits of a plant’s lifespan are. To that end, researchers have attempted to verify the age of various plants to determine what types of plants can live the longest and also identify individual specimens that may be especially old. Of all plant varieties, certain species of trees have the longest lifespans.

There are complications when estimating the lifespan of a plant, however. First off, it is difficult to measure the age of a tree. The age of an individual plant is generally calculated based on observed growth rates in our current environment, which may not be the same as they were previously when conditions might have been much different.

It’s also necessary to distinguish what counts as an individual plant for the purposes of measuring age. While this may seem straightforward at first, it can actually be complex because some plants reproduce asexually or are part of a clonal colony. A clonal colony refers to a group of individual plants that grow together, and originate from a single ancestor. Since they are reproducing asexually from the same source, all individuals in a clonal colony are genetically identical.

Clonal colonies are quite common among plant species, although they may appear to be individual plants to the casual observer since the colony is underground. Clonal colonies pose a challenge when trying to identify the age of a plant since the colony can continue to live and reproduce for much longer than any single individual plant within the colony.

Finally, there are a few species of plant that can undergo long periods of inactive dormancy after which they can return to normal growth given the right conditions. It is unclear whether or not we should consider dormancy periods to be part of an individual specimen’s lifespan when comparing with other plants that are consistently alive by the normal definition.