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Pruning is an art that many homeowners are hesitant to try. Amputating parts of a plant can feel like minor surgery; what if you mess up?
Yes, pruning a plant can kill it. However, it is very difficult to kill a plant unless you take off enormous chunks of plant material or prune too heavily for an extended period of time.
The more you know about pruning, the less likely you are to lose a patient. Read on for how to avoid fatal pruning mistakes and tips on best pruning practices.
Pruning Mistakes That Kill Plants
Most pruning mistakes do not kill plants immediately. Fatal cuts are extremely difficult to do on accident, and most plants are so resilient that they can resprout from a mangled stump.
Plants that die from pruning are victims of death by a thousand cuts. Each cut done incorrectly opens a plant up to infection, freeze damage, or extreme stress.
As pruning continues to damage the plant each year, it becomes weak and dies prematurely.
Correct pruning improves the health of a plant gradually, while incorrect pruning does the opposite. The good news is that most pruning mistakes can be fixed over time.
One of the most common pruning mistakes is to prune during the wrong time of year. Plants handle pruning differently depending on the season.
Timing depends on the growth cycle of each plant and why you are pruning in the first place. For example, you should prune a peach tree in the early spring before the leaves emerge to encourage lots of first-year growth for fruiting.
If you prune too early in winter, or before the tree is fully dormant, you can do major damage to the health of the plant. Plants going into dormancy are storing up energy, and if you cut off healthy branches during this time, the plant may not be able to break dormancy with enough vigor.
Pruning during temperature extremes also exposes cuts to freeze damage or rot, depending on the weather.
Always look up what kind of plant you want to prune and when it responds best to pruning. Most plants should be pruned in late winter to early spring.
Most plants should not have more than 1/3rd of the healthy plant material removed. If the cuts are made correctly, plants can heal from the stress of pruning as long as enough plant material remains to generate new growth.
If you remove more than 1/3rd of healthy growth, the plant may not be able to make enough energy to replace what was lost.
If a plant is pruned too much too often, it will have to focus energy on healing rather than new growth, which slowly cripples a plant’s health.
Root pruning can be an effective method of rejuvenating old root systems, but it is easy to mess up and difficult to fix.
You can prune the roots of established trees or shrubs by cutting through roots with a shovel or loppers. This type of pruning should be reserved for more advanced gardeners who know how much they can remove without doing any structural damage to the plant.
Incorrect root pruning can result in weak trees or shrubs that can fall or are unable to pull up enough water and nutrients.
Most severe pruning wounds are the result of not understanding plant anatomy:
- Topping. If you remove the apical meristem (see this article for more detail), the tree can no longer grow taller, and it will greatly shorten its lifespan.
- Meristem damage. If you cut too deep into a meristem or remove it completely, the cut may not heal and it can cause an infection or severe heat/cold damage.
- Dirty pruners. Some diseases are passed from plant to plant through surfaces like pruners (source). Dip or spray pruners between each plant to prevent spreading harmful pathogens.
- Conifers. Evergreen trees with needles should not be pruned unless there is damage. These branches will not grow back like deciduous trees. Instead of pruning, conifers should be candled.
Although rare, there are a few cuts that can almost immediately kill a plant:
- Crown removal. If you cut into or cut off the crown (base) of a grass, the plant will be unable to produce new growth.
- Trunk removal. This should go without saying, but if you cut a tree down to below the first branch, it will die.
- Splitting. Some perennials can be divided and replanted, but most deciduous plants will die if they are split in half at the base.
Helping Plants Heal from Pruning Errors
So, what if you make a pruning error?
Most plants can come back from severe pruning damage if you begin to prune with small, directed cuts that encourage new growth.
Some damage may be irreversible, like removing large lateral branches or topping a tree, but you can still prune for shape and new growth to extend the life of the damaged plant.
If you have a plant that has pruning damage, help it heal by doing the following:
- Begin fertilizing. Research the plant and start fertilizing the plant as recommended. Too much fertilizer can harm the plant further, but consistent nutrients can help the remaining healthy tissue grow stronger.
- Water consistently. This does not mean to water frequently. A damaged plant may not be able to handle drought stress, but overwatering will cause just as many problems. Water consistently enough to prevent drought stress.
- Mulch. Mulch helps with the overall health of the plant by retaining moisture, adding nutrients, and providing a home for beneficial insects. A thick mulch layer can help maintain a healthy foundation for a recovering plant.
- Repair pruning. As you learn more about pruning, you can start making a plan for how to fix the plant. Most pruning mistakes take a few years to fix, so don’t try to correct a bad cut in one day. Do smaller, more frequent pruning sessions (as long as they are in season) to try to direct new growth into filling in bare spots or growing a stronger trunk.
The most important part of helping a plant recover from poor pruning is time. With enough time, even the most ugly pruning jobs can be reshaped.
How to Prune Without Doing Damage
Damage usually looks like stubby or jagged cuts, and large amounts of plant material missing.
The best way to avoid damage is by making clean cuts and removing no more than 1/3rd of healthy plant material.
A sharp, clean cut heals quickly, which helps minimize the risk of infection. Plants will scab over a proper cut and move on with new growth as long as you have not damaged the meristem.
It is always more damaging to leave dead or diseased plant material than it is to remove it.
The 1/3rd rule only applies to healthy plant material; branches or stems that are infected or broken can reduce the life of a plant, so removing them is always recommended.
Make a solution of 1 part bleach to 9 parts water and dip or spray the pruners between plants. This prevents transmitting diseases, which may infect a plant through an otherwise properly-placed cut.
Pruning is one of the most important maintenance tasks for deciduous plants, but it’s easy to do more harm than good if you don’t understand basic plant anatomy. Luckily, most pruning mistakes can be fixed over time.