Is Pruning Necessary?
In nature, do you see trees being pruned? Are there bucket trucks cruising our forests cutting off parts of branches? What would you say if you found someone trimming up a tree in the wild?
These questions sound preposterous, but yet urban trees are routinely subject to questionable or unnecessary trimming and pruning. And people pay money to have it done!
Strictly in terms of tree health, pruning is seldom necessary. If done incorrectly a tree can be structurally and physiologically weakened, subject to disease and pests, and horribly disfigured. Trees are mostly capable of regulating their size and shape without human interference.
Why then do our local trees get mistreated?
Largely tree abuse happens because humans lack an understanding of how a tree works. A thorough explanation of tree physiology is beyond the scope of this page, but some key facts about what trees need can be conveyed without that knowledge.
Always Have a Reason
The first, most important principle in tree care is to have a reason before doing any tree work. Locally, much tree work is done pointlessly, and that work is done in a way that is actually harmful to tree health.
For the most part, good reasons to prune, trim, or remove trees are clearly evident and require little expertise.
Some Good Reasons to Seek Tree Care Work
- Included bark between co-dominant leaders
- A limb (or the whole tree) is potentially dangerous
- Mushrooms or fungi are evident on or near the trunk
- Looks like it's dying
- Fix mistakes of past tree work
- There are 2 limbs growing parallel vertically with included bark
- Improving structure
- Tree removal
- Fruit tree management
Some Poor Reasons to Seek Tree Care Work
- Make a tree grow faster
- Balance the roots
- Tree is too big / limbs are too long
- Make top bushier
- Because your neighbor just did his tree
- Thinking "trees just need trimming" to be healthy, akin to a haircut
- Pruning to eliminate balls, fruit, seeds, etc.
Neither list above is exhaustive, but the key concept is to avoid pruning a tree just for the sake of doing something.
Tree topping is not a recommended practice, but it is common in our area.
"Topping" is the act of arbitrarily heading back branches; in other words, shortening long limbs. See the pictures below for examples of what NOT to do.
Long branches on this tree were arbitrarily shortened
An attempt was made to artfully shape a tree by heading back limbs
This is what happens when a branch is headed back (made shorter)
This tree was shaped to a bowl shape by heading back limbs.
Heading back limbs causes a tree to replace the branch with numerous small branches that are weakly attached to the remaining limb. The new growth can cause a wind sail that may increase the chance of tree failure.
In most cases tree topping permanently ruins the form and structure of a tree. This is the best case scenario. When a weak, old tree is topped, it can bring the onset of the "spiral of death" which will hasten a tree's demise.
Don't top your tree!
How To Prune Trees
Assuming you have a valid reason to prune a tree, you should try to make thinning cuts. Thinning is the act of removing entire limbs, rather than part of a limb. If you prune back to another branch that is at least 1/3 the diameter of the branch you removed, there is a good chance that you will not get a proliferation of new limbs. This will minimize the effect on a tree's health.
There is a proper procedure for pruning limbs. This page by the Morton Arboretum gives a brief overview of the process. Please note that ownership of a chainsaw does not guarantee the operator knows how to prune correctly.
Hiring a Professional
Like many professions, tree care providers vary in their skill and ability. Tree work should be done by experienced, knowledgeable providers.
ISA Certified arborists will usually be a safe bet to perform work or advise you competently. Not all tree work requires a certified arborist, however.
We recommend talking with any potential tree service before hiring. Getting quotes from multiple companies may help you get a better price and possibly get a sense about their competence.
Ask questions such as:
- Do you do thinning or topping?
- Will you use a 3-cut method to remove limbs?
- Ask for work to be done according to "ANSI A300"
- Ask to see an example of their work
- Are you insured, etc.?
The best tree companies are usually very busy. It's a good sign if they can't come right over. Be patient.
There are many commonly held misconceptions about landscape trees. These ideas often lead to poor management choices.
- Trees have long taproots. While saplings may have long taproots, most of a tree's roots are in the top 12 inches of soil. There simply isn't enough oxygen to sustain really deep roots.
- Roots grow toward water. Not really. Roots proliferate where conditions are best. That means access to water, nutrients, and oxygen. They have no sense of where water may be until they run across it.
- Use Myccorhizae and root stimulants at planting. These seldom have measurable effect in field conditions.
- Wood chips and pine needles make soil acidic. This has been shown to be false.
- Deep watering draws roots down deep. Water to completely fill the root zone for sure, but any extra is just wasted water. You see pipes giving irrigation "deep root access" but there are few roots below 2 feet. See our irrigation page for watering information.
- Prune tops of trees to balance the roots at planting. The thinking behind this is false. Trees will generate the crown and roots they require. Your interference can be harmful.
- Seal all pruning cuts. Pruning sealer is not recommended. It interferes with the process of protecting a tree from infectious agents.
- Topping invigorates trees. Heading cuts cause local invigoration at the expense of overall weakening. Don't top a tree.
There are a couple good resources about some common tree myths. Learning more about trees is your best tree care decision