I have addressed this topic in the past but have recently noticed more companies that are removing the lower and inner branches of trees. This practice is called "lion’s tailing" because it removes all lateral branches on main stems, leaving foliage at the ends like the puff of hair at the end of a lion’s tail.
Lions tailing is not a recommended pruning practice. It was done for several years with the thought that removing branches from the lower canopy would reduce wind-load and as a result reduce the chance of branch breakage. While this seems to make sense to some, it does not hold true.
In fact, removing viable branches on the inner canopy shifts the wind-load to the top of the tree instead of the mid canopy. This shifts the point of maximum stress higher in the tree and onto smaller branches that are more prone to breakage under the wind load.
You can test this theory by putting rags on the eyelets of a fishing rod. If you distribute the rags between on all of the eyelets and wave the rod you will feel how the load is evenly distributed. If you place rags only on the tip and wave the rod you will feel pressure on the rod is closer to the tip which increases leverage and moves the point of highest tension closer to the tip where the rod is thinner and has less strength.
In addition to the physical forces, lion’s tailing also has detrimental effects on physiological or growth responses within the tree. Removal of lateral branches reduces foliage that provides the food for growth in that part of the tree. This reduces the development of branch taper or thickness where viable branches had been removed.
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The leaves on these inner branches also have morphologically different because the environment on the inner canopy is different than the outer canopy. Different layers of the canopy function most efficiently during different weather conditions. Trees produce foliage where it most benefits the tree, so removing foliage in an entire portion of a tree can have very adverse effects on tree health.
When inner branches are removed, the tree responds by developing new branches where live lateral branches had been removed. These are called epicormic shoots, or water sprouts. This results because dormant buds that had been suppressed by terminal buds of the branch start to grow. These branches grow rapidly and are poorly attached, so many of them eventually break out of the tree.
A third response can be increased decay in lateral branches, which can further weaken them and make them more prone to future breakage. Every time a branch is pruned off, the tree is opened up to decay. Trees have the capacity to respond and contain decay as long as wounds are not too large or too numerous. Lion's tailing also removes foliage and reduces the tree's ability to respond to the numerous wounds that are created.
The arboriculture industry has very specific guidelines for pruning trees that are based on research. If you are having trees pruned, seeking out properly trained arborists and following their advice on pruning will provide the best long-term results for your trees.
One of my biggest concerns with improperly done tree work is that it not only impacts the individual tree but it also forms impressions among the general population where others are likely to adopt poor practices. At that point, poor practices start to impact the entire urban forest.
