Anyone performing tree trimming service for hire in California must be licensed by the Contractors State License Board if the price of the service is $500 or more. Landscapers who perform any kind of tree trimming, tree removal, pruning, grinding of stumps or limbs or who "engages in tree or limb guying" must be licensed, says the California Code of Regulations. The licensing process serves to protect consumers from tree trimmers that do not meet state requirements, and provides an additional avenue of redress if the consumer experiences a problem with the tree trimmer.
The question of who owns or has rights to trim a tree is integral to who can trim it. In California, a person is considered the owner of a tree if that tree's trunk is located on the person's property. This means that even if the roots grow onto another person's property, that other person does not have an ownership claim to the tree, according to California Civil Code section 833. However, if a tree trunk is located on the border of two or more properties, California Civil Code section 834 states that the tree belongs to the property owners in common.
Encroaching Roots and Branches
When a tree owned by one person extends over the property line into the property of another owner, the general assumption is that the encroached-upon owner can trim the tree branches or roots back to the property line. However, California courts have ruled that the property owner trimming a tree he doesn't own has a duty to act reasonably. The pruning must take into account the health of the tree, and damaging the tree to the extent that the tree's health suffers leaves the pruner liable for damages.