Pruning Trees and Shrubs
Pruning trees and shrubs is similar to giving a haircut. Unfortunately, in many cases a plant can’t outgrow a bad haircut. Learning how a plant responds to pruning will help you understand how to maintain the natural beauty and shape of the plant.
It’s important to learn which plants are deciduous and which are evergreen. Deciduous and evergreen plants are not only pruned differently, they are pruned at different times of the year. Take a plant sample in to a nursery or your local Cooperative Extension office if you aren’t sure which type of tree you have.
Before you prune, make sure your tools are newly sharpened (many nurseries offer tool sharpening services). Also, wear safety goggles to protect your eyes and gloves to protect your hands.
Pruning a plant removes leaf buds and dominant shoots to help plants grow more uniformly. The root system of a pruned plant remains the same size, and the buds left are supplied with more water and nutrients. The result is a plant that puts out vigorous new growth.
Use a hand pruner for small cuts and loppers or a pruning saw for larger branches. Cut out dead, diseased or damaged branches first. Always exercise caution when pruning so you never accidentally cut into the main trunk of a tree or shrub, as this invites pests and diseases to attack the tree. Allow the plant to heal itself, do not use “tree seal” products which are unnecessary and slow down healing time.
Deciduous Trees and Shrubs
Deciduous plants experience dormancy during cool weather, and often have beautiful fall color followed by leaf drop. Examples of deciduous trees are Chinese pistache and liquidambar trees. Examples of deciduous shrubs are rose of Sharon and flowering quince.
Newly planted deciduous trees have specific pruning needs when young. Make sure to read Tree Training and Pruning before you begin to prune.
The best time to prune deciduous plants is during dormancy, when you can see the “bones” of the plant. First prune out dead, diseased or damaged branches. Then, decide how to shape the plant and make your cuts accordingly. Pause in between cuts and examine the effect each one has on your plant so as not to over-prune.
Deciduous plants may also be pruned lightly during spring and summer. Aside from pruning out dead, diseased or weak branches at this time, you can also do corrective pruning. If some of your winter pruning cuts didn’t shape the plant the way you wanted, now is the time to prune and redirect that growth. Just remember, never prune plants severely, as removing too much foliage during warm weather can expose previously shaded branches to direct sunlight and result in sunburn. Sunburned branches attract pests and diseases which weaken the tree.
Evergreen Trees and Shrubs
As the name implies, evergreen plants have green leaves year-round. However, they also shed these leaves year-round. Examples of evergreen trees are pine and southern magnolia trees (Magnolia grandiflora). Examples of evergreen shrubs are boxwoods and junipers.
The best time to prune evergreen plants is in early spring, before they start to grow. Evergreen trees and shrubs do not need much pruning, except to maintain shape. Pruning before spring allows the plant to fill in quickly and hides pruning cuts. When pruning is done after spring, unattractive bare spots are the result. You will need to wait until the following year to try to correct these.
When pruning, it’s important to note that tree topping is a practice discouraged by the ISA (International Society of Arboriculture). Tree topping creates unsightly trees that become a high cost hazard. When a tree has 50-100% of the crown removed, this essentially starves the tree of food producing leaves and causes it to grow more quickly than usual to replace the lost foliage. This rapid new growth is weak and prone to breaking. A topped tree is a stressed tree which is unable to defend itself from sunburn, diseases and insects.
In many cases, tree topping is done because the wrong tree species was chosen for the site. For example, large trees growing under power lines are often topped on a frequent basis. Caring for these trees is expensive as well as dangerous. For healthy trees, avoid tree topping or any kind of severe tree pruning. Read Choosing a Tree to make sure you plant the correct tree for your site.
Sketch by Ed Perry, photos by Holly Guenther