Tag Archives: bark inclusion

Also This

The other day I wrote about bark inclusion.

The UK arborist I mentioned there, Dr. Duncan Slater, has done extensive field work to document the conditions under which bark inclusion appears common.

It shouldn’t be a surprise.

If we start from the premise that, in the same way that our physical strength is developed by the strain we put upon our muscles, tree “strength” is developed in part by the strain that gravity and wind put upon wood, it makes total sense that anything preventing a tree from experiencing that strain can be detrimental to it.

And often it happens that a tree will be naturally deprived of that necessary stress or strain.

Credit: Duncan Slater

Slater calls these “natural braces.” For example, a branch from one of two equal-sized trunks of the same tree — these are called “co-dominant stems” or “double leaders” — may fuse with the second trunk. Obviously, the two parts of the tree are more nearly frozen in place. What Slater has discovered is that under such conditions, the junction between the two trunks is more likely to be weak due to bark inclusion.

So if that’s true, it’s obviously very important to eliminate a natural brace when a tree is young, but if a tree with a natural brace is older, cutting out a natural brace may be a recipe for disaster, i.e., a tree service may be increasing the chance of the tree splitting and falling on someone.

And look what I found recently in this Freedom Park oak with co-dominant stems:

Bark Inclusion

If you happen to be a tree, one of the bigger challenges you have is this: I need energy to grow and reproduce! So I’m gonna reach for sunlight, water, and nutrients. But how far and fast can I reach before something like this happens?

The photograph above shows an American elm (Ulmus americana ‘Princeton’) planted years ago by Tree Watch and Trees Atlanta in Freedom Park.

American elm is really great at reaching. It can grow fast. When it’s at home — ‘home’ being rich, alluvial soil in a forested floodplain along a river or stream — a tall American elm will have channeled so much of its energy into growing upward, in order to reach that lovely sunlight at the top of the forest, that it may have no branches at all until the 50- or 60-foot mark.

Photo credit: Christian O. Marks

Of course, an American elm growing in an open, grassy section of Freedom Park has no difficulty at all accessing sunlight. It’s like a kid left alone in a candy shop. (Think of that poor elm tree in Freedom Park as a kid with a terrible tummy ache.)

Continue reading Bark Inclusion