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Occasionally while tramping through some wooded area I’ve noticed trees that form a right angle then another in their trunk. Think of the shape from foot to head of someone sitting in a chair. I’ve never understood what would make a tree do that but I may now have at least one answer.
Half a dozen years ago, give or take, I planted an Austrian pine in the back yard close to where we now have the patio. I hoped it would provide additional screening of the houses across the fence before I got so old and blind I couldn’t see them anyway. A pine-tip moth larvae got to its growing tip and killed it. That seems to be something nursery trees are vulnerable to. I think the moth must infest the area of the nursery that grows them. Although I have had a number of trees afflicted, they were always ones newly planted. I’ve never seen established trees damaged by the larvae.
A larvae attack that kills the growing tip can mess up the appearance of tree, keeping it from having that nice conical, Christmas tree look. But as you can see from the series of photos at the top, a tree can create a new growing tip from a branch close to the dead tip. The first photo shows the dead original tip. The second photo shows the tree overcoming the damage by creating a new top from a limb. Note the knee-like bend it creates.
The third photo is of a tree in the east lane that was similarly damaged by larvae. It has not created a new growing tip and has simply turned into a big bush. Why hasn’t it created a growing tip like the other tree? Here’s my theory: The tree in the backyard is shaded by a pecan and a juniper. It’s adaptation to its circumstances is to grow up toward the sun. The tree in the lane is not shaded, at least in the morning, and apparently doesn’t need to grow up as much as the first because it gets the sun it needs in the morning. Over time it will grow taller but it doesn’t look like it will ever have the Christmas tree-like shape whereas the one near the house will be a curiosity in coming years.