Whether you have a forest of trees on your property or just one or two in your backyard, you’ll need to prune and/or thin trees now or at some stage in the future. You don’t have to be a professional tree trimmer or pruner to do proper pruning or tree thinning, but it helps to know the difference between the different tasks.
So, what is the difference between tree pruning, tree thinning, and tree trimming? While all three involve removing branches from trees, the procedures are all quite different. When you prune a tree, you cut off dead or excessive branches. When you trim trees, you cut or prune them to shape them. When you thin trees, you remove branches to allow sunlight to penetrate and air to circulate.
What is pruning?
Pruning is a term we commonly use when talking about generally cutting the branches off trees. This may be to remove dead wood, improve the shape of trees, or make them grow stronger and better.
But the terminology can be confusing. Ultimately, what you do when you cut or prune trees will depend on what you want to achieve.
Treeco in Florida, a business in the tree industry, talks about the differences between tree trimming and tree pruning. They discuss crown thinning as a type of tree trimming rather than tree pruning.
In its free online publication How to Prune Trees, the United States Department of Agriculture (USDA) has pruning guidelines for the crown thinning of trees. In a document titled Pruning Cuts, Colorado State University Extension has a section on Thinning cuts that they describe as natural target pruning cuts.
In a paper, Pruning trees and shrubs, gardening experts from the University of Minnesota Extension explain that pruning by removing branches is done to promote plant health, and maintain and improve the appearance of trees and shrubs. But they don’t mention trimming or thinning.
Confused? Me too.
What is thinning?
When you thin plants, including seedlings, you remove those that are too close together. This enables the strongest and healthiest plants to thrive.
Mechanical thinning of trees in forest locations is similar but done on a much larger scale. This type of thinning, as the USDA explains, reduces the risk of fire and helps to keep forest trees healthy.
But in a garden environment, you are more likely to be thinning trees to allow sunlight to filter through the foliage. This reduces diseases of the leaves by increasing airflow.
A University of Florida paper on thinning the canopy of landscape plants says thinning is what keeps the inside branches of trees alive and makes them stronger. The aim is to have an even distribution of branches along each of the limbs, so they don’t group toward the ends.
When thinning, you shouldn’t be removing the branches from the interior of the tree. You need to remove small branches from the outside and middle sections of the main branches.
When crown thinning, you don’t remove entire branches. Instead, you selectively cut off branches within the crown of the tree.
Benefits of Pruning
Pruning is intended to thin, reduce, and/or shape the branches and larger limbs of trees. It promotes new growth and usually increases the flowering and fruiting potential of those trees that produce fruit, nuts, and so on.
When you remove dead or diseased branches, pruning will ensure the tree continues to grow in a healthy manner. It will also help the tree to become stronger so that it withstands storms and high winds.
Pruning also provides a tool to form plants into specific shapes and control their size.
Benefits of thinning
When you thin trees, you open up the canopy to let in sunlight and air. This encourages the leaves to grow and it decreases the risk of disease.
Even though it’s a form of pruning, thinning pruning shouldn’t affect the shape or size of trees.
Difference between pruning and trimming?
While you might think that tree pruning and tree trimming are the same, here are a few differences cited by Treeco.
In essence, pruning means selectively removing diseased or broken branches. It also means making them less dense to prevent them from breaking.
There are several types of pruning cuts including removal cuts where specific branches are removed. Reduction cuts are intended to reduce the overall size of trees.
Heading cuts rely on making cuts in the tree trunk or main stem of plants. The heading cuts that you make remove the growing tip of a branch.
The cut encourages more buds and results in denser growth. You can also use heading cuts to control the size and shape of trees.
While some say that the aim of thinning is primarily aesthetic, it undoubtedly also keeps trees healthy. For example, tree trimming includes crown thinning, which lets sunlight and air penetrate through the crown of the tree.
Trimming also includes crown cleaning, where you remove dead and diseased branches from the crown of the tree. Crown reduction is when you trim the outer branches of trees to reduce their size.
Other forms of trimming are crown raising and crown restoration. Crown raising involves removing lower branches close to the ground
This makes trees look between and allows more light to reach the ground around the tree. By removing damaged or diseased branches, crown restoration promotes new growth.
When do you prune?
In general, the best time to prune trees is in early spring or late winter when the plants are dormant. You do, though, need to be careful with spring-flowering plants because you don’t want to remove their buds.
Late spring or early summer is a good time for so-called spring bleeders. This is because the leaves that are growing reduce the bleeding, and the cuts heal more quickly.
When do you thin?
The best time to thin trees is in late summer or early fall. You can also thin in winter.
It’s not a good idea to thin in early summer or spring because thinning tends to attract insects.
Pruning, thinning, and trimming are all related activities that are beneficial to the growth and development of trees. For home gardeners, the differences may be subtle, but they do matter.
What matters most is that you keep your trees healthy, and pruning, thinning, and trimming are key when it comes to this.