The native tree species population is a significant part of the City of Los Angeles ' urban forest. In recognition of native trees' contribution to the natural environment, the citizens and government of the City enacted an ordinance to protect them against removal or damage.
Native trees are very sensitive to environmental changes, such as: changing of original grade within the dripline of the tree, over watering, particularly in the summer months, and over pruning.
For the most part, native tree species require little or no pruning other than periodic removal of dry wood. In fact, the pruning of green tissue increases the probability of disease organisms gaining entrance into a tree. Pruning of native trees should be limited to the removal of dead or diseased limbs in fall and winter months with no heavy pruning at any time. Occasionally, a mature tree may benefit from a light thinning (removal of 10 to 20 percent of live green foliage) to reduce the weight of branches and to open foliage for light penetration and reduced wind resistance. Pruning may also be required to provide vehicular and pedestrian clearance and/or to provide clearance from buildings and other infrastructure such as traffic control devices, streetlights, and energized lines.
Native trees should never be severely pruned. Severely pruned trees are unsightly and respond with vigorous, weakly attached growth that is susceptible to powder mildew. Large pruning wounds are also more subject to decay . To prevent the spread of disease, climbing "gaffs" shall not be used at any time when pruning Oak trees.
Although pruning of native trees on private property does not require a permit from the Urban Forestry Division, all native tree pruning should comply with the International Society of Arboriculture "Tree Pruning Guidelines"; The American National Standards Institute " Trees, Shrubs and Other Woody Plants Maintenance Standard Practices" (ANSI A300 ); and the City of Los Angeles "Tree Trimming Standards" to ensure proper pruning practices.
This information sheet is provided as a public service. Hopefully, it answers the important questions regarding the pruning of native tree species. If you have any further questions, please contact the Division at (213) 847-3077.
As a covered entity under Title II of the Americans with Disabilities Act, the City of Los Angeles does not discriminate on the basis of disability and, upon request, will provide reasonable accommodation to ensure equal access to its programs, services and activities.