Botanist Lens: Rings of Life

Oak stump cross section.

Towering the tallest canopy layers in the woodland gardens at London Town, you will mostly find the grand Willow Oaks, Pines, Red Oaks and Tulip Poplars. Disease, drought, water logging, insect damage, there are many reasons for loss of a tree. When a tree is cut down to its base, as sad as it is to lose one of the oldest members of the canopy, it exposes the beautiful arrangement of the rings of life. The rings of the tree visible in a stump section reveal much more than the age of a tree. It also shows the stressed time zones in its life span as well as the healthy ones.

Each spring and summer a tree adds new layers to its main trunk. In spring, the wood grows faster and is lighter because it consists of larger cells. The wood growth in summer is slower than spring and thus the summer wood has smaller cells and is darker. The spring and summer growth of rings appear as alternating rings of light and dark wood.

Spring and summer bands of dark and light.

The rings seen in the cross section of a tree tell more than just the age. The rings tell a story of the phases of stress a tree has seen in its life cycle. Disease, drought spells, tree competition, nutrient stress, there are ample stories revealed in a wide cross section of a stump.

Pine tree trunk cross section. Counting from the center, about 35 rings in, you will notice the rings getting tighter, this shows onset of periods of extreme stress.

One of the cross sections’ pictures of the trunk with this post shows that at around 35 years of age, the Pine tree went through a long-stressed period when water and nutrient content was low. Also, the rings look closer as the tree grows half its length due to stress from competition with other canopy layers.

Recently, we lost a huge Red Oak, Pine and some others that gave way to disease or just were at the end of the lifecycle. Every year London Town gardens does a tree survey with Integrity Tree Service to check on trees that are dying or have dead wood. Sometimes the dead trees are apparent if you look at the top 'Crown,' and sometimes, the bark gives indicators.

Integrity Tree Service

Barks are an excellent way to look for tree stresses: mushrooms growing on the base of a tree, excessive lichens, sawdust and holes on the trunk, splitting at the base, there are many early indicators to watch for. But most often there aren't any good indicators for sudden stress related death. For eg. a prolonged drought, very excessive water logging, fungal disease, any of these on top of added stress can lead to sudden death.

Maple on its last lag. The mushrooms at the base are an indicator of the sudden end of the Maples lifecycle.

A century old Willow Oak gradually lost to disease

In woodland gardens, losing trees to stress, age or diseases is a given. Losing the tallest canopy layers can be good when it opens up large sun windows, but it can be detrimental to the undercover growth that was used to its deep shade. That’s why at London Town we are actively looking at adding successional canopy layers.

It is easy to fix the loss of small shrubs, but it takes years to replace the tallest layers. Successional canopy cover planting is done for reforestation but is also key for woodland gardens. Follow us in the coming months to learn more about what layers are we replacing our dead tallest trees with.

Beautiful weaved Tulip Polar bark. We are watching closely for any splits/damage to the base.


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