Tuesday, July 18, 2017

I Go To a Friend's House to Settle an Argument and End Up Giving Them Way More Grief Than Even I Expected

I went to a friends house for lunch to check out a tree. The situation was that he and his wife had a little disagreement about whether or not a branch should be cut from it. I wasn't looking forward to being in the middle of a spousal disagreement but I knew my friend and his wife and didn't think it would be a big thing. The tree in  question is a California pepper (Schinus molle). The trees common name is a misnomer, as it is native to Peru. If the number of questions I receive about it is any clue, it is one of the most problematic trees in Southern California as well as one of the most popular. Since before the turn of the century, and maybe even since the early 1800's, these trees have graced ranchos and farms here. Unfortunately they can be very short lived if they are watered too frequently, sometimes only 40 years before rot starts causing large limbs to fall off.

My friend's California pepper tree. 

At first glance my friends tree seemed fine. It was just over five years old and had a large canopy, probably 30-40 feet wide, and the canopy was lush and luxuriant. The branch in question could have been pruned off or left as is, so I didn't have to take sides in my friend and his wife's argument. But there was something else...

I first noticed that some string lighting that had been placed on the tree was cutting into the trunk, so I mentioned it should be removed. Secondly, the tree was in a lawn, California pepper trees should not be planted in lawns, nor should lawns be planted around them. I then noticed something far more serious: the tree had a defect that could not be resolved and would result in my recommending the tree be removed.

Looking at the base I noticed a problem that has no happy ending -the trunk was an even diameter from about 8 feet up to where it entered the soil. It had no flair. Lack of any flair at the base of the trunk generally means that the tree is doomed to failure way before its time. It is caused by planting a tree that is rootbound. This sets up a situation where the trees own roots literally strangle the tree's trunk, preventing it from growing wide at its base. This messes with the fundamental physics of the tree.

Trees need a flaring base so that the roots coming from the base can form a 'plate' under the ground that  helps support the tree. This is so the center of gravity of the tree is always above the roots that are supporting it. If the center of gravity is allowed to lean over that support and becomes positioned over soil where their are no large roots to provide a surface for the tree's weight to act on it through the force of friction, then there is nothing keeping that tree up and it fails.

Now add to that the effect that the much narrower than normal trunk has on the tree -it raises its center of gravity. So where a normal tree would have a center of gravity that's maybe about a normal person's shoulder height it instead has a center of gravity located up in the canopy of the tree so that it is much easier for the wind to push the tree's center of gravity over the supporting root area and cause the tree to fail. The tree is basically too top heavy.

But that was not all, it was also showing signs of imminent failure. The tree had a noticeable lean and opposite the lean a mound had developed adjacent to the tree. This may indicate that the tree is already starting to fail; the weight of the tree could be pulling these vitally important supporting roots straight out of the ground.

So my recommendation was, unfortunately, to remove the tree and either plant a new one or choose another type of tree and plant that instead. In my next blog entry I will discuss some of my favorite trees for backyard shade, so stay tuned.

Also notice the tree is leaning to the left. 

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