Think about oak, pine, jacaranda and orange trees. Each species has its own natural shape and size, and good pruning techniques will maintain this character. Trees have to tough it out where they grow in spite of damage from wind, insects, or pruning, and have evolved the ability to replace lost limbs. However, this replacement is like repairing broken sidewalks–serviceable, but not always attractive and safe.
As a tree grows, the size of the root system keeps pace with the growth of the shoot system, ensuring that the water and nutrient supplies stay in balance with the capacity for energy production. If too much of the tree is pruned, trees such as elms may actually die from the shock. In other species, the trauma triggers growth from dormant buds to replace the lost photosynthetic capacity. This results in vertical “water shoots” along the branch or creates ugly tufts at the cut ends. Often so much growth is stimulated that more pruning is necessary the following year. This regrowth obscures the natural shape and beauty of the tree, and is often more weakly attached to the main branches than the original branches were, decreasing safety.
There is a misconception that all trees must be pruned regularly, and that severe pruning one year will reduce costs the next. It’s true that many trees grown for fruit or flower production require annual pruning. However, if trees grown for beauty or shade are chosen with regard to their eventual size and shape, they will require little pruning. As trees mature, the need for pruning often decreases. For most trees, any pruning that is done should take place in the fall or winter when growth is slow and when birds aren’t nesting.
Of course, dead and diseased branches should be removed, and any safety issues should be addressed. Sometimes a few lower branches might be removed to allow more light to plants growing underneath, or a few branches may be removed or shortened to improve shape. The crown may be thinned a bit to allow more light or wind through the canopy. However, when trees are pruned, it should generally be no more than 25% of the bulk of the tree, and often much less. If branches are cut back it should usually be to a smaller ‘replacement’ branch about one-third the diameter of the one that is shortened. If a branch is removed, the cut should be made just outside the “collar” where the branch is attached so that the wound will heal. Cuts at other points can leave unsightly stubs that will die. Trees should never be topped, be given a ‘bowl cut’, or have most of their internal branches stripped off. Even if the tree survives, regrowth will be ugly and the tree will be less healthy. A well-pruned tree will not look pruned, it will just look naturally attractive.
Trees not only add beauty to the landscape, but provide shade and moderate high temperatures, thus decreasing water loss and energy costs. They help reduce air pollution and contribute to property values and to the character of Claremont. Every year, dozens of the private trees in Claremont suffer from poor pruning. This not only ruins the attractiveness of the trees and much of their usefulness, it often results in greater costs to the homeowner. Trees in nature are not pruned and we like the way they look, so it makes sense to go carefully.
More information on proper tree care can be found at the Sunset website (sunset.com) the educational website of the International Society of Arboriculture (treesaregood.org), and the Sustainable Claremont website (sustainableclaremont.org). Take a look at the trees on the college campuses and in the City parks. In the long run, proper pruning saves both trees and money. The Claremont Sustainable City Plan calls for the production of a list of competent arborists, so if you know of a good tree trimmer, please send the information to Sustainable Claremont--and throw away cards from any trimmers advertising topping!