The Importance of Tree Pruning
Why, When, and How to Prune Trees
Sometimes when driving through my neighborhood and looking at the landscape, I’m reminded of the misconceptions that people have about pruning trees.
The myths say that any time of the year is a good time to prune a tree, and anyone with a chainsaw or a hand saw can do it.
The reality is a little different.
Certain times of the year are better for pruning trees than others, and thinking about why you’re pruning your tree can help you do it properly.
Why Should You Prune a Tree?
The most important and obvious reason to prune any kind of tree is to get rid of dead, diseased, or damaged branches.
This doesn’t just keep people, pets, and property safe from any large limbs that could fall. It also promotes the health of the tree by preventing the spread of disease and ensuring that the tree uses energy to grow only the branches that are vigorous and intact.
But pruning doesn’t just have to be practical or done in the case of an emergency. Trimming and removing a tree’s branches can improve its look and the way it functions as part of a landscape:
- Controls a tree’s overall size
- Encourages flowering, fruiting, and growth of certain parts of a tree
- Prevents larger, dead limbs from falling
- Removes useless parts like suckers and water sprouts that look thin and don’t contribute to a healthy canopy of foliage
Nothing transforms an outdoor space like a tree that’s safe to stand around and pleasant to view.
When Should You Prune a Tree?
Technically, you can prune both deciduous and evergreen trees throughout the year, and you might have to if you find branches that are diseased or broken.
However, certain times of year are better for a tree’s health.
Late Winter and Early Spring Pruning
Surprisingly, the cold, grey stretch of time from February to early April is considered the best time to prune for green growth in deciduous and evergreen trees alike. Oak trees are best pruned between December and February due to their susceptibility to a disease called oak wilt in warmer months.
Pruning trees in late winter or early spring gives them time to heal the cuts before the heart of spring arrives. The result is a rush of green growth during the primary growing season.
Pruning before leaves have begun to develop also allows you to see the branches better and locate problems that foliage otherwise might hide.
Plus, if you’re caring for trees such as linden trees that flower in the summer, pruning in late winter will help those flowers bloom.
Late Spring and Early Summer Pruning
Pruning at the onset of summer is a way to control a tree’s shape and appearance. Instead of interrupting the heady spring growth, you’ll be able to influence future growth by seeing how much leaf surface the tree has and determining where to cut to best reduce it.
Also, although foliage might hide some problematic branches, it can reveal others by showing which limbs are weaker and less capable of supporting the canopy’s weight.
Early summer pruning is recommended for trees that flower in the springtime, such as lilacs and cherries. In this case, you'll make your cuts after the tree's flowers have dropped, not before they bloom. This way, you won't miss out on their annual display!
Late Summer and Early Fall Pruning
Early fall pruning is not recommended for two essential reasons:
- It promotes new growth at a time when that growth is more likely to be killed off by increasingly colder temperatures
- It creates wounds easily infected by fungi that are more active in fall
Due to these reasons, pruning during the late summer or early fall is advisable only for the most problematic branches that risk safety or the tree’s health.
How Should You Prune a Tree?
Safety and Tool Care
Whenever you’re working with sharp tools and dropping heavy objects from a height, there are basic safety guidelines to observe.
First, be sure to wear proper safety gear:
- Thick gloves
- Safety glasses
- A hard hat any time branches might fall from a height above you
- Items specifically recommended for chainsaws (safety chaps and hearing protection)
Next, never climb a tree or a ladder to prune, or prune next to power lines. Any task involving these dangers should be left to professionals who are certified, licensed, and insured.
If you are not a professional, stick to pruning shears, hand saws, and pole saws for tree trimming. Use a chainsaw pruner only on limbs lower than shoulder height, and again, never prune near power lines.
Finally, taking care of your tools involves not only keeping them sharp but also cleaning them:
- Between one tree and another
- After removing a branch that shows signs of disease
- At the end of each pruning session
Carefully wiping the blades of your pruning shears or the cutters on your saw’s chain with alcohol and allowing the alcohol to dry will do the trick.
Tips for Pruning Trees
It’s best to start pruning when a tree is young and hasn’t developed unhealthy or awkwardly positioned branches. Even though pruning sometimes can’t be avoided, the goal is to prune less each year as a tree grows older and more established.
Trees can be pruned using two kinds of cuts:
- Heading cuts
- Thinning cuts
Heading cuts involve removing the growth buds at the ends of branches (also known as terminal buds). These cuts are used to reduce the total length of each branch and determine the overall shape of the tree’s canopy.
Heading cuts are best made on branches younger than a year old. Heading cuts made on older branches tend to encourage water sprouts, which are the thin, vertical, poorly supported branches that sprout along the top of a longer limb.
To make a heading cut, trim a branch back to about 1/4" in front of one of its lateral buds (the buds found all along the sides of the branch). Any one of the lateral buds will do; it depends simply on how long you want the branch to be.
Thinning cuts are the cuts more commonly used on mature trees to remedy several problems:
- Water sprouts
- Heavy branches
- Branches that rub against other branches
- Branches that connect to other branches or the trunk at too great or too narrow an angle (45-60 degree angles are best)
A thinning cut involves cutting a branch all the way back to the point where it attaches to a larger branch or the trunk of the tree.
But wait! Before you prune a branch, take time to identify the branch collar and the branch bark ridge:
- The branch collar is a swollen mass of tissue at the base of the branch where it attaches
- The branch bark ridge, which might be harder to see, is a raised section of bark at the point of attachment
Make your thinning cut flush against the branch collar (and if visible, the branch bark ridge), but be sure to leave the collar intact to help the cut heal.
If the branch you’re cutting is larger than 1” in diameter, use the three-cut pruning method recommended for large boughs.
And save your pruning chainsaw or pole saw for limbs 3” in diameter or greater! Using a chainsaw on smaller limbs risks damage to the bark and other essential plant tissue.
Do I Always Need to Prune?
Sometimes pruning isn’t the answer. Sometimes a tree will be so badly damaged, ridden with disease, or overgrown and unmanageable that felling the tree is the most practical solution.
However, don’t give in to the myth that cutting down a tree is the only solution. By pruning a tree smartly and consistently, you can make healthy arbor practices and beautiful trees your reality. Always consult a certified arborist when in doubt or if the task becomes greater than you anticipated.