Proper, selective pruning can frequently be used to control pests without pesticides as well as prevent future infestations. This is especially the case with plant diseases. However, improper or unnecessary pruning can severely damage trees by causing wounds which are entry sites for insects, decay and disease organisms. Pruning can require a degree of skill as well as a fair amount of specialized knowledge on when and how much to prune depending on the plant species. The general guidelines provided at the end of this section should allow successful pruning of moderate size landscape plants in many of the routine situations likely to be encountered by facilities managers.
SAFETY ALERT! – Only qualified arborists should prune large trees or those near power lines.
For more information on proper pruning, readers are encouraged to consult the UC ANR publication Pests of Landscape Trees and Shrubs. Minimize future pruning by selecting species that mature to a size appropriate for that location (“You cannot prune a big tree to make it a healthy small tree no matter how you try” *)
- Respect the natural form! (do not try to make a round tree tall and thin or vice versa)
- Prune plants properly when young and small to minimize the need to remove large limbs later
- Prune out pests confined or concentrated in a small area of the plant
- Prune off limbs that are infested with wood-boring insects
- Make pruning cuts correctly to minimize the likelihood of disease
- Prune deciduous trees during the winter when they are dormant
- Avoid drastic pruning by doing a little each year
*Shigo, Alex L. 1989 Tree Pruning, a World-Wide Photo Guide. 143