Brenda Altman of the University of California Agriculture and Natural Resources discussed the effects of severe tree pruning in a blog post published on Apr. 1. Altman described how trees that were overpruned last fall received chemical signals to grow new leaves, but the timing led to challenges due to reduced sunlight during winter months.
Altman explained that while some regrowth began in November, limited sunlight meant the trees could not produce enough energy. As spring arrived with more sunlight, further growth was observed, but she warned that “there will not be enough leaves to give the energy to replace all the stored reserves of energy they have lost.” She also noted potential consequences for homeowners, such as higher indoor temperatures and increased noise from nearby streets due to reduced shade and foliage.
According to Altman, overpruning can result in weak branches and less habitat for birds. She said this may lead to shorter tree lifespans: “The trees will survive, but for how long? The pruning and recovery shorten the life of trees.” However, she pointed out there would be fewer leaves for homeowners to rake in autumn.
Altman recommended never removing more than 30% of a tree’s foliage during one pruning session. She advised making cuts at branch nodes rather than indiscriminately trimming branches. For those unsure about correct techniques, she suggested consulting an arborist or contacting their local UC Master Gardener office.
The University of California Agriculture and Natural Resources (UC ANR) supports its programs through public contributions according to its official website. The organization is part of the University of California system and manages Cooperative Extension services according to its official website. UC ANR operates nine research and extension centers across California’s diverse ecosystems according to its official website.
UC ANR promotes sustainable practices designed to strengthen resilient ecosystems and economic vitality according to its official website. It conducts nearly 34,000 educational events each year with support from over 18,000 volunteers according to its official website. Through these efforts—delivered via workshops and partnerships—the organization extends university research throughout all 58 counties in California according to its official website.