Part Two: Prune Trees Like a Pro
In my recent blog about pruning I discussed why we prune trees and the best time to prune them. This week, we will provide you with four easy-to-follow steps on how to prune young trees as well as tips to make the pruning process as painless as possible for you and your trees.
Step 1: Assess the Tree Holistically
One of the main reasons we prune is to improve branching structure, thereby lessening threats from weather damage, pests, and disease. To help you determine what should be removed, walk all the way around the tree, checking it from top to bottom for any visible structural issues.
- Top: look for a strong, straight main leader (trunk) with not too much upward competition (fig. 1, below left). Some species, such as river birch or understory species like redbud, may have a multi-stemmed or shrub-like form instead, in which case don’t worry too much about eliminating competing trunks.
- Middle: keep an eye out for any lateral limbs that are too close together, that cross one another, or that have too narrow of an angle between the branch and the trunk (fig. 2, below right).
- Bottom: identify “suckers” or new sprouts from the base of the tree, as well as any dead, diseased, or broken lower branches.
Step 2: Decide which cuts to make
We do not want to remove more than 25-30% of a tree’s canopy, or leafing structure, in one year. For trees that are badly in need of pruning, that may mean prioritizing the most urgent issues and waiting until next winter to address others.
- Performing “tree-age” can be a delicate balancing act. Focus first on anything that is causing immediate damage to the tree (branches with open wounds or splits, crossing limbs that are rubbing against each other, etc.) before moving on to trimming back or “subordinating” competing leaders and basal sprouts.
- Removing branches for spacing can wait up to three years if necessary.
- Lower branches on young trees should be left until they are 1″ in diameter since they help to promote strong, proportional trunk growth.
- Branches that are already dead do not count towards the 25-30% since they aren’t contributing to the tree anyway and can safely be removed at any time!
Step 3: Make the cuts
Make sure you have the right tools at your disposal. We use hand pruners for small branches, long-handled bypass loppers for branches up to 1″ in diameter, and arborist saws for branches greater than 1″ in diameter. Loppers and saws are also available on extendable poles up to 12′–we borrow ours from the Baltimore Toolbank for about $1 per week.
- Keep your tools sharp! Your cuts will be more accurate and a cleaner cut will heal more quickly. You can use a metal file to sharpen pruners and loppers.
- Make cuts close to the nearest lateral bud and at a slight angle (fig. 3, above). Remember that whatever energy the tree would have sent into the branch you are removing will now go to the next lateral bud(s), causing fuller and faster growth in new directions–important when guiding future structure!
- Do not cut flush to the bar–leave the branch collar (fig. 4, below left), which the tree uses to compartmentalize damage.
- For branches larger than 1″ in diameter, use the three-cut method to keep the branch from stripping away the bark below as it falls (fig. 5, below right).
- Be careful not to accidentally slice or scrape branches behind or below your target that you did not intend to remove. We do not want to create more problems than we solve!
Step 4: Follow up
When you prune, you are literally wounding the tree and creating permanent scars–but that doesn’t have to be a bad thing.
- “Painting” or dressing pruning wounds is not necessary and in some cases can be detrimental to tree health. We do not recommend it.
- Check in on your tree during the next growing season to ensure that the cuts are scarring properly and not falling victim to insects, moisture, or fungal damage.
- Revisit your tree every winter or at least every 3 years to re-assess structure and make any additional needed cuts.
If you ever have questions about diagnosing or treating a badly diseased tree, or removing limbs on a large mature tree, please consult a professional arborist.
Pruning is an art as well as a science–it is one that I myself am still learning, and that I will continue to learn for many years to come. Nevertheless, I hope these steps will provide some guidance to you as you care for your own trees.
For hands-on experience, sign up for one of our remaining winter pruning workshops!