As I’ve already discussed veteran trees can be very old indeed and by their very nature have had to go through some real hardship to reach such a grand old age. So how do they do it?
Firstly trees are made of wood, a little obvious I know but wood in its own right is an amazing material. Wood is laid down in rings, each growing season the tree will increase its width by tiny increments. As the cambium, which is the living part of the tree just below the bark, grows the inner most part dies and a chemical called lignin sets it in place. The lignin and cellulose form a hard structure that we know as wood. This is incredibly strong and is the reasons trees can grow so much taller than any other plants as they reach for the light. Different species of trees grow wood with different properties – oaks and yews that grow very slowly tend to have very hard and strong wood while ash have wood that splits very easily hence its scientific name Fraxinus. The strength that wood gives trees means they can withstand the elements and stay standing for centuries.
The second reason that trees live so long is their size. Smaller plants run the risk of being eaten and trampled by various animals and being over shaded by other plants. When trees do get damaged they are often large enough to shrug off that damage, a small hole punched by a woodpecker can be tolerated without really slowing the tree down.
The third reason for a tree’s longevity is their ability to adapt and regenerate. We think of tree roots as being very solid, timeless structures when in fact a tree’s roots can die back and be replaced depending on conditions and damage at an amazing rate. Roots can reposition themselves depending on changing water availability or ground conditions. In fact if a tree falls and comes into contact with soil new roots can sprout from the trunk.
This ability to regenerate isn’t limited to what happens below ground. If a tree loses its main branches it can regrow them. In fact it’s a natural part of trees life to lose many of its highest branches as they become too far away for the tree to transport water and nutrients to them and they grow new fresh shoots from the main trunk. This is a process called retrenchment and can happen several times during a trees life. In fact retrenchment is what leads to many of the features that make veterans so valuable for other wildlife.
So trees are hard to start with, large enough to resist attack and able regenerate when damaged and this is why we have some trees that might predate William the Conqueror.
Tree Trivia: Oak trees are statistically more likely to be struck by lightning than other trees because they are often the tallest species around and because their wood has a lower electrical resistance than most. This pattern hasn’t just been noticed by modern scientists as the Vikings associated oaks with their thunder god Thor and the Greeks before them with Zeus. The Druids also worshipped oaks; in fact the word “druid” may have come from an ancient Celtic word for oak.