Like water and sunshine, tree pruning is an essential contributor to overall plant health. Especially in climates like Portland, Oregon, that experience variable weather, pruning keeps trees producing leaves, fruit and flowers effectively. Pruning trees helps maintain structural integrity by balancing the weight distribution of branches on each side, clearing dying or dead wood that may be at risk of falling and removing branches that cause a tree to be top-heavy.
Pruning fruit trees actually makes them more productive. It’s recommended that a surprising amount (about ⅓) of fruit tree growth is removed through pruning. Pruning within a few weeks of transplanting (the sooner, the better) helps a newly planted tree focus its energy on developing strong roots. Pruning immediately after transplanting also prevents transplant shock. Fewer branches means less energy is used to maintain branch, leaf, flower and fruit production, and can therefore be directed toward the plant’s root system.
The second phase of fruit tree pruning is focused on production; removing excess foliage or weak branches that can break under the weight of fruit and redirecting a tree’s energy towards the parts viable for production.
Ornamental trees, those that do not produce fruit, may also need pruning. Branches encroaching on city sidewalks or streets or limbs interfering with a building or home may need to be removed. Diseased limbs threaten other trees while damaged or dead branches are at risk of falling. Pruning is a detailed craft that requires both general knowledge of trees and a good set of tools. Before getting started, identify these crucial points on your tree:
- Nodes are the points on a branch where the buds, leaves and small branches originate. Nodes look like little bumps along the bark and usually stay through dormant winter months, though in some species they may fall off. A tree’s nodes play a crucial role in healing a pruned plant.
- Internodes are the sections of branch between nodes. Besides providing structural support, internodes carry food and water to the life-giving nodes. In most trees, nodes are spaced at least a couple of inches apart by internodes. Only trees with closely-spaced nodes like dwarf conifers can be pruned into topiaries.
- A collar is the point at which a branch is connected to the trunk or to another limb. The collar contains the proper tools necessary for a tree to heal a wound, which is actually the process of compartmentalizing. The collar helps cut tissue form a callus and stops the wound from becoming infected or infested with bugs.
- Suckers are any growths sprouting from the base of the trunk. Suckers often appear as green twigs that look like miniature trees. They literally suck nutrients from a tree and should be removed via pruning as soon as possible.
The Three Ds and the CACs
It’s important to remove parts of a tree that are consuming energy and will not provide any benefits. Removing branches that contain any of the “three Ds” is the first step in pruning, followed by the “CACs”. Here are the first six things to look for when analyzing which parts of a tree need to go:
- Dead branches or limbs exhibiting brown or dried foliage, rotten wood or bare branches.
- Dying branches indicated by parts of leaves that are turning brown or prematurely dropping leaves.
- Diseased branches that have brown, black or yellow spots on leaves or light brown spots (scabs) on fruit.
- Clustering usually occurs at the top of a branch where many leaves occupy a small section of the tree. Because they’re crowded, they likely won’t produce fruit. In the event that they do produce, clusters are structurally weak and prone to snapping.
- Acute branches are connected to the tree at sharp angles and are weak parts of a tree. Acute branches are at risk of snapping once they bare heavy fruit that cause branches to bend. If branches form a perfect “V”, they’ve got to go.
- Crossing branches restricts airflow between branches, leading to potential disease spread, and damage caused by branches rubbing.
Common Pruning Mistakes to Avoid
Having the right equipment will greatly improve your chances of a successful pruning and understanding basic tree anatomy will help you avoid crucial errors. Here are some common mistakes made by novices and how to avoid them:
- Using dull tools won’t produce the clean cut necessary to maintain a healthy tree. It’s necessary to sharpen saws, loppers and hand shears regularly, and to always use shears with bypassing blades.
- Using anvil blade pruners instead of a pruner with bypass blades is a crucial error. Anvil systems use one blade that is meant to meet a flat plate. Whereas bypass systems contain two blades that cleanly cut through a branch, anvil blades cause damaged tissue by crushing or ripping wounds into branches.
- Not cleaning tools between cuts when working with diseased trees spreads diseases between trees, just like it would in humans. Keep diluted bleach in a spray bottle and use it, along with a clean rag, to disinfect your pruning tools between jobs and between cuts when working with a diseased tree.
- Cutting through a tree’s collar or removing it completely is a common mistake among novice arborists. Collars contain everything a tree needs to recover from the exposure of pruning. When cutting, it’s crucial to cut as close as you can to the collar without causing damage. Don’t leave any of the limb.
- Making one cut instead of several can be dangerous for both you and the tree. It’s important to thoroughly plan out your approach before starting to make cuts. When pruning, think of your approach as divided between “A” and “B” cuts. The aim of your first few cuts should be to get the bulk of a branch out of the way so you can clear your work area and set yourself up to make a precise second cut. Lightening the load by removing the bulk of a limb will reduce the risk of tree bark being ripped from the trunk when a limb is removed. Making several smaller cuts will produce the same effect as one large cut and will be easier for a tree to recover from.