28. Deer rut
What is it and will my tree survive?
Last week, something gnawed at the bark of my recently planted Katsura tree. Today, I noticed that the same damage occurred to a Sango Kaku Japanese Maple on the other edge of the property. What is going on?
Then I found the google search answer to my quandary: deer rut.
What is deer rut?
Deer rutting season is from middle of October to early December when deer mate.
Why does this matter to my young trees?
As rutting deer rub their antlers on tree trunks, they strip the bark. Nutrients for a tree travel through a thin layer near the bark, called the Phloem. If that gets too damaged, the tree will die.
The victims
Here is the damage on my two young trees (Katsura on the left and Japanese Maple on the right):
Close-up of the damage
Overview of the tree
Here is another look at this Japanese Maple. Notice that not only is the bark rubbed off, but the top of the tree is missing. The damage starts around one foot off the ground and it goes all the way up to about five feet. Sigh.
The Prognosis
Now the next question: will it survive?
Assess the amount of damage
I have read that if more then 50% of the circumference of the tree trunk is damaged, the tree will not survive. Why? Because nutrient for the tree travel through the thin layer located near the bark — the phloem — and if too much of it is missing the tree is unable to get enough nutrition. Based on this assessment, it was the right decision to cut down the Katsura since the damage was more than 50%. The damage on the Japanese Maple was more varied. I will leave it as-is for now and see what happens.
Phloem
Want to learn more about the layers of a tree? Check out this excerpt form “How A Tree Works” an article I found from https://treescharlotte.org/
a) Bark: The outer layer of the trunk (and branches) is called the outer bark or just the bark. Its texture, thickness, and flexibility depend on the type of tree. Although bark looks different from tree to tree, it serves the same purpose—to protect the tree from injury and disease. Some trees have very thick bark that helps prevent damage from fires. Others have bad-tasting chemicals in their bark that discourage hungry insects. And some bark is covered with spines or thorns that keep browsing mammals away.
b) Phloem: The layer next to the outer bark is called the inner bark or phloem (FLOW-um). The phloem acts as a food supply line from the leaves to the rest of the tree. Sap (water containing dissolved sugars and nutrients) travels down from the leaves through channels in the phloem to the branches, trunk and roots, supplying all the living parts of the tree with food. If you were to cut a band around the trunk through the bark and phloem, the tree would probably die. That's because the phloem would be severed and food could no longer flow to the lower trunk and roots.
c) Cambium: Next to the phloem is a very thin layer called the cambium. It is often only one or two cells thick, and you need a microscope to see it well. The cambium is a growth layer of the tree making new cells during the growing season that become part of the phloem, part of the xylem (see below) or more cambium. The cambium is what makes the trunk, branches and roots grow thicker.
d) Sapwood/Xylem: The layer next to the cambium is called the sapwood or xylem. Each year the cambium adds new layers of woody tissue; the sapwood is made up of the youngest layers of wood. The sapwood is a network of thick-walled cells that forms a pipeline, carrying water and minerals up the tree from the roots to the leaves and other parts of the tree. The sapwood also stores nutrients and transports them across the tree, from one part to another.
e) Heartwood: Most of the trunk in an old tree is dead wood called heartwood. The heartwood is old xylem that no longer transports water and minerals up the tree. (After a few years the sapwood in most trees gets filled in with resinlike material and slowly changes into heartwood. The new xylem is the only part of the wood that works as a transport system.) The heartwood is often much darker in color than the sapwood. The heartwood gives the tree support, but sometimes it rots away leaving a hollow, living tree.
The next step is to research and implement deer rut tree protection. We have a lot of deer, so this annual problem is not going away.