How do you prune an oak tree

How to Trim an Oak Tree Without Killing It

Date November 11, 2021

Author David Gaona

A beautiful oak tree is an asset to any landscaping. As an essential part of our ecosystem fostering many food sources and habitats for birds, plants, and wildlife, how can we help keep them healthy and thriving wherever they may grow? Here are some top tree tips for doing just that!

Can Trimming Kill an Oak Tree?

Absolutely, and when it comes to oak trees, age matters! If your oak is 3 years old or younger, you can snip the dead or damaged branches to minimize potential disease risk that might further harm the entire tree; if older than 3 years, limbs that have turned back inward towards the trunk should be removed entirely. With the dead limb gone, your trees can now focus on supporting their existing appendages and any possible regrowth! Trimming oak trees allows for better distribution of tree nutrition and room for other branches to grow more consistently.

Carefully Trim Only in the Winter

Timing of pruning matters for most trees, but it’s an especially critical consideration for oak trees. Only ever prune oak trees in winter. They can develop an often fatal disease known as Oak Wilt, spread by infected pests attracted to any open wounds (e.g., from branches rubbing against each other or pruning cuts) and feeding on the sap from the freshly shorn trees. These bugs are most active in the warmer summer months between April and October, so your best chance to avoid them is when they’re dormant in the cold.

Speaking of pruning cuts, they can be very helpful in stimulating new growth, but be careful as extremely cold temperatures can spoil all that help, too. As it gets closer to winter, plants reduce their energy use and convert it to reserves. If any growth is encouraged at this time, it will misuse those resources and lead to dieback in the event of a freeze.

Another factor to consider is the lack of foliage in winter. Leaves can impede your view of where cuts need to be made to the tree’s structure, risking improper cuts and stress to the tree. Oak trees don’t exactly handle extreme pruning well, so be very intentional and thoughtful of which limbs you snip. Never trim off more than 15% of the branches at any one time. If in any doubt about your pruning plans, give an ISA-certified arborist like TreeNewal a call to help you make more confident decisions.

Best Pruning Practices

More like what best NOT to do! Here are 4 common mistakes when it comes to the cutting methods.

1. Heading cuts

  • This cuts a branch back to an indiscriminate point that may ultimately disjoint the natural regrowth pattern. Occasionally, a heading cut is appropriate, but it’s best to leave that call to tree trimming experts.

2. Lion tailing

  • The removal of interior branches and leaving the leaves and growth only at branch ends. Lion tailing will remove too much foliage needed for photosynthesis and leave the tree vulnerable to wind damage and sunscald. It will also improperly redistribute weight to the weaker ends of branches and increase the presence of water sprouts, which are a sign of stress that the tree is developing new growth too quickly to compensate for photosynthesis.

3. Flush cuts

  • Perhaps the most common pruning mistake, a flush cut, happens when a branch is pruned flush with the point of attachment. This action critically disturbs the branch collar, the enlarged tissue at a branch’s base necessary to produce a cap over the pruning cut. If the wound cannot be naturally sealed, the cut becomes an accessible entrance for pests and bacteria to sneak in and harm the tree, if not outright kill it.
  • Be sure to cut just past the collar to leave encouraging room for the wound to seal itself.

4. Stub cuts

  • These are essentially the antithesis of flesh cuts. Stub cuts happen when a limb isn’t pruned closely enough to the branch collar; here, the stub is too long for the tree to form a seal over the wound.
  • An essential rule of thumb: If a hat could hang off the branch stub, it’s too long.

INSTEAD, use the 3-cut method!

To avoid bark damage caused by an unwise singular cut to a large branch, split the process into 3 clean steps.

  • Make the first shallow cut on the underside of the branch roughly 1 to 2 inches out from the branch collar where the branch attaches to the trunk. It will help avoid any tearing to the bark should the branch fall unexpectedly during the cutting.
  • Then, cut approximately 2 to 4 inches from the branch collar to remove the limb. Only a modest stub should be left behind at this point. (Remember the critical rule of thumb!)
  • Lastly, remove the remaining stub by cutting slightly past the branch collar.

What To Do After Pruning

To give your trees the best chance for success, apply a pruning sealant to all wounds, no matter the season. This waterproof petroleum-based paint spreads over the exposed area and acts as a bandage to protect the tree underneath as it heals. Be sure to properly dispose of any removed questionable branches to help manage and prevent the spread of disease.

If you feel overwhelmed and need assistance caring for your Texas oaks from professional tree care experts, don’t hesitate to drop a line to the ISA-certified arborists at TreeNewal for tailored tree care advice.

To learn more about How to Trim an Oak Tree Without Killing It, call our Argyle and Southlake-based teams

at tel:(817) 592-6846 or send us a message.

We’re a little different than the average tree services company.

Learn more about TreeNewal’s ISA Certified Arborists!

Our Dallas/Fort Worth-based tree doctors can explain how sustainable tree care services add more value to your bottom line.

Healthy trees, healthy lives.

Tips for Trimming Oak Trees

Trimming and pruning are essential grooming techniques that enhance the growth of a tree and help maintain its good health for a long time. Regularly trimming oak trees is important to ensure that your yard doesn’t start to resemble a jungle with overgrowth or unsightly branches that don’t look well-maintained. Trimming is important for both aesthetic and health reasons of the oak trees around you. So, if you are hesitant to take up the trimming of oak trees or you do not have the time or equipment, you can always hire a tree service in your area. But before you start trimming yourself, there is some basic information that you need to know.

We present to you the top 5 tips that you need to know before trimming oak trees. Spread across important categories, these tips will make the job easier for you, in the absence of an arborist.

To begin with, you should understand where the oak tree comes from, what weather does it like and what are the factors that make it thrive, without causing any dangers to your property or the foundation of your building.

  1. There are about 400 species of oak, identified all over the world.
  2. Mostly, the tree is native to the northern hemisphere.
  3. A mature oak tree can grow up to 30 meters in height and spread up to 25-45 meters in diameter.
  4. They require meticulous care to keep them healthy and disease-free.
  5. They cannot tolerate heavy watering and apart from a good regular tree trim, they also need to be protected from weeds.

Now, let’s get on to understand the right way of trimming oak trees, if you want to do it yourself.


Although you can always turn to a professional tree service, there are times when knowing how to trim an oak tree can come really handy. There could be situations when professionals are not available as per your schedule or you need to help a friend with trimming oak trees. In such cases, your knowledge about the tools, their use and the basic knowhow of pruning can be very useful in saving the day. So, here is a brief 3-step guide on how you can finish the task successfully and without causing any harm to the trees, to your yard or to yourself.

Step 1: Get your tools in place

Before you start to trim oak trees, you need to have the right set of tools with you. This also includes all the protective gear that you should be using for your safety. Some of the most essential tools that you will need:

  • Pruning shears
  • Lopping shears
  • Rope saw
  • Limb saw/buck saw
  • Pole pruner
  • Chainsaw
  • Hardhat
  • Safety goggles
  • Pruning sealant

All of these tools are very helpful when trimming oak trees as they have their unique individual uses, designed to ease out the whole trimming and pruning process.

Step 2: Clean the equipment

Before you start using the tools, you should make sure that they are clean. Simple water and household bleach can serve the purpose. Also, make sure to dry them and in case you have more than one oak tree that you have to trim, clean and dry the tools between every tree. This minimizes the risk of spreading diseases or infection from one tree to another when you start to trim oak trees.

Step 3:  Follow proper technique for the branches

You should make yourself aware of the branches that need to be gone before you start to trim oak trees. The branches you choose also depend on the age of the tree.

  • For an oak under the age of 3 years: Only trim the dead or broken branches.
  • For an oak over the age of 3 years: Remove branches that seem to be growing towards the centre of the tree.

When you are more confident about how to trim an oak tree, these precautions will become second nature to you. They are important so that you don’t accidentally kill the tree.

The next step is to understand when to trim oak trees. The weather and the time of the year play a crucial role in ensuring a successful tree trim. So, always keep these weather-related tips in mind when you have to go ahead with trimming oak trees.


The final tip for successfully trimming oak trees is about the times of the year when it is ideal to do so. Ideally, winter is the best time to trim oak trees. And that includes the months between November and April. This is key to preventing the trees from a lethal disease called oak wilt. It is a fungal disease caused by insects buzzing around any wounds in the tree bark or feasting on the sap of a newly trimmed tree. Besides, these bugs can also carry the disease from one tree to another. In a nutshell, it can be very painful and hard to deal with once it starts spreading, posing a serious danger to all the trees on or around your property. In the colder months, the chances of these bugs contaminating the tree wounds is far less.


Knowing when to trim oak trees  and how to trim an oak tree is important and when you follow the guidelines, your plants should be safe. However, there are chances that a tree or a tree branch can break off accidentally during the vulnerable summer days or during their growth season. You need to take special care of the trees in such cases and make sure to keep the said branches from the aforementioned bug attack. A protective tree sealant can be used in such cases as a form of dressing for the tree wounds. In addition, whether or not you are trimming oak trees, it is important to keep an eye on their health throughout the year and call for professional help in case you suspect anything wrong.


You can go about it in one of the two following ways.

One, you could make a schedule for trimming oak trees at regular intervals. For younger trees, pruning every 2 to 3 years is ideal while for older trees, it can be every 3 to 5 years.

Alternatively, instead of following such a generic timeline, you call professional arborists from Panorama Tree Care to inspect your tree, its health and its individual pruning needs. They can then suggest a more personalized tree trimming plan for your oak.

Concerning safety reasons, it is important that you take all the right protective measures when trimming oak trees. In case you feel that certain branches are near dangerous positions like power sources or greater heights that are not too accessible to you, calling for professional help is the smart way out. And if you have budget constraints, you can always ask the professionals to only take up the most difficult parts while you can handle the smaller branches and cleanup work yourself.

You can call us anytime for a free consultation regarding the health and trimming needs of your trees. We care about all yards and all kinds of plants. So, it would be a pleasure offering you all the information we have and figuring out the perfect ways in which we can help you with your tree trimming requirements.

90,000 when and how can I cut the oak


  • The role of an oak in landscaping
  • The role of trimming in the formation of the crown
  • ,
  • Cunning of the Austrian oak
  • Cunning a stone
  • Acts of actions
  • When they proceed to pruning?
  • Sanitary pruning
  • Recommendations for beginners

Oak is a majestic and magnificent tree, a symbol of solidity and durability. The ancient Roman scientist Pliny considered centuries-old oaks a wonder of the world and believed that they appeared simultaneously with the emergence of the universe.

In nature, you can see about 600 species of this plant, among which there are both evergreen and deciduous. Basically, these are trees 20-30 meters high, less often 50 meters. Some species are shrubs, among which there are very small ones, no higher than two or three meters. Oaks adapt well to different environmental conditions, some species can withstand frosts down to -60C. In Western Europe and central Russia, pedunculate oak is most common, and, for example, in North America, the species composition is more diverse.

The role of oak in landscaping

Most of them grow slowly, in addition to the main trunk there is a spreading crown, which is a heavy skeletal branches and many small branches covered with dense foliage. To maintain an aesthetic appearance, the crown of each oak must be cut. This, seemingly simple at first glance, must be done carefully so as not to spoil the landscape composition and not harm the plant.

Where natural conditions favor the growth of oak trees, there are quite a lot of them in forest parks and large parks. Separately growing trees, the tree looks wide, its trunk is not high, and the crown is spreading. Most often they are planted next to coniferous trees.

If this is a planting and a lot of trees are planted, then the oaks will be tall, straight and slender.

The role of pruning in the formation of the crown

Throughout the life of the plant, intensive growth of the main stem can be observed. Apical growth occurs much faster than lateral shoots, so oak belongs to plants with monopodial branching.

Regardless of the species, the ever-growing trunk of the plant will be strong and straight, but it may not be alone. A randomly growing crown will give the plant an untidy look, so it needs to be shaped, that is, to limit the growth of branches. To do this, oak branches need to be cut in a timely manner, they do it every two to three years, using different methods.

To slow upward growth, remove the apical bud (remove the tip of the shoot), shorten or cut out the branches or shoot. Some gardeners make the mistake of believing that it is enough to trim only the growth. Such a procedure will lead to the fact that the branching will be even more intense, which means that the thickening will increase. In order for the crown to look openwork, it is better to remove part of the growth, and sometimes entire branches, this should be done without sparing, since as a result it will be possible for sunlight to enter the crown.

Pruning of crowns of oaks of different types has a number of minor differences.

Austrian oak pruning

Austrian oak is a deciduous tree with a domed crown. Crown pruning is done while the plant is at rest. The best time for this is autumn - spring.

This procedure is carried out according to the requirements for stem trees, which must have a main trunk, the stem should be about 2.5 m high. In countries with short and cool summers, the apical shoot will not be characterized by accelerated growth, as a result, the plant will look like a bush.

The first three to five years, the trunk is cleared of the lower shoots, but the branches are shortened gradually, this will take 2-3 years. Pruning formed trees is to remove dead shoots, this should be done regularly. If you still have little experience in pruning, it is better to entrust this matter to professionals. In order to properly carry out anti-aging pruning and remove excess branches from the crown, knowledge and skill are needed.

Holm oak pruning

Holm oak is an unusually beautiful plant. It has a wide rounded dense crown and dark glossy leaves. The shape of the crown, especially in young trees, is different - both drooping and columnar, but, most often, an intermediate option. Young representatives of this species resemble a bush; over the years, the trunk becomes clearer. The tree needs regular shearing, planting such oak trees you can get a magnificent hedge, you can grow one tree, if you form a crown in a timely manner, it will be large from the middle to the end of summer.

Pruning requirements are the same as for stemless trees, the lower branches in the shade tend to fall off. The main shoot will not remain dominant for long, but you should not rush to remove the side ones, gradually they will take over the functions of the skeletal ones. In old oaks, the crown is asymmetric, but your attempts to restore harmony may be in vain, young shoots are unlikely to appear in empty places. Mature oaks are pruned only in emergency cases, for example, if the branch is broken by the wind, but it is better to entrust this to an experienced specialist.

Very often, out of ignorance, small, beautiful hanging branches are cut, this does not have the best effect on the appearance of the oak, therefore, it is necessary to make a decision on raising the crown only after consulting with a specialist.

Algorithm of actions

As we have already said, a neglected tree not only looks untidy, but can also become a hotbed for the spread of a dangerous infection that poses a threat to other trees. That's why it's so important to trim in a timely manner. With the right tool and knowledge of the algorithm of actions, you can easily cope with the task.

  1. Specify the type of oak and ask when is the best time to cut it. Pruning times can be adjusted to suit the weather conditions in your area.
  2. With a sharp instrument, make cuts on the lower parts of the branches at a distance of 30-60 cm from the main trunk.
  3. Make cuts on the upper parts of the branches 7-10 cm above the first ones. This will keep the bark intact.
  4. It is necessary to remove undeveloped, damaged and dry branches. Cut as close to the trunk as possible to minimize knots. The cut points are treated with sealants; black paint can be used as a sealant.

When do you start pruning?

The best time for this is the end of winter and the beginning of spring, but, as we have already noticed, different species have their own characteristics. In areas with a warm climate, where winters are not very cold, pruning is also done in winter, but the air temperature on this day should not be lower than -5C. If this requirement is not observed, then part of the bark and wood in the area of ​​\u200b\u200bthe cut may be frostbite. No less careful should be pruned in the summer. Pruning should not be too intense.

Sanitary pruning

Mid-February or mid-April is the best time for sanitary pruning of oak trees. Cut off dry, unhealthy, damaged branches, and those that grow towards the center of the crown. You can also do this from July to August.

Beginner's advice

  • The chainsaw is most commonly used for pruning. Keep safety in mind, and if you are handling it for the first time, consult an experienced gardener on its use.
  • Do not cut thick old branches without the help of a professional or alone, there is a high risk of injury.
  • Oak is a tall tree, so experts do not recommend standing on the stairs while working, it is better, for reliability, to fix yourself to the trunk with seat belts.
  • If you consider pruning unnecessary, long branches will grow uncontrollably, they will show wounds from neighboring branches and knots rubbing against branches from gusts of wind. The wounds will develop an infection. What will affect the health of the tree is not the best way.
  • Take care of your own safety before starting work. Wear a hard hat or headgear that can protect your head. Any protective clothing with long sleeves is suitable - a work suit, overalls, a dressing gown and even a shirt.

How to prune an oak? Step by step ▷➡️ Postpostmo

Oak is a tree known for its incredible resistance to temperate climates and the changing seasons. Where, as for other species, pruning is an important process for the development of this tree, so we invite you to continue reading to discover ¿ how to trim oak ?


  • 1 What is Oak?
  • 2 Care for holm oak
  • 3 Pruning oak
    • 3. 1 What time of year is oak pruned?
    • 3.2 pruning tools
  • 4 How to trim oak?
    • 4.1 How to prune a young oak tree?
      • 4.1.1 Form pruning
      • 4.1.2 Fruiting pruning
    • 4.2 How to prune a mature oak tree?
      • 4.2.1 Cutting products
      • 4.2.2 repair pruning
  • 5 Oak pruning tips

What is Oak?

Oak is a type of tree from 16 to 25 meters high that can be found mainly in Spain but also in other regions of southern Europe. It is known to be very resistant to drastic seasonal changes in parts of Europe and is also a species with a very long average lifespan.

Quercus Ilex is the scientific name for oak, cataloged as one of the most common Outdoor plants resistant to cold and heat in Spain is due to the fact that it is adapted to living on almost any type of soil. Its grandiose crown is capable of casting a shadow over a very large area, and it has a very strong trunk.

It has beautiful leaves that can remain always green regardless of the surrounding climate, although it should be noted that you may see some traces of yellowish color on the leaves when the tree reaches the senescence stage.

Oak blossoms between March and May, although it should be noted that its main attraction is not the flowers, but the fruits known as acorns, which are used as food for a huge number of wild animals. and is also used to make flour.

Its wood is incredibly hard, so much so that some types of structures are even made from it, although their manufacture is a complex process. It is also very common in the home of the Spaniards, who use it for making fires, in addition to the fact that its bark is also often used to color certain materials.

Caring for holm oak

One of the best aspects of this species, besides its resilience and adaptability to a large number of regions and climates, is that it is extremely easy to care for this type of tree, so it is very easy to grow this type of crop. types.

As we have already said, holm oak adapts to almost any type of soil, and in fact there is very little land where this tree can be planted, which contributes to the expansion and reproduction of this species.

Incredibly hardy in cold climates, however it is best kept in areas where the climate is drier and warmer most of the year. Sunlight is an aspect that is very conducive to the development of this tree, although it does not prevent it from forming in shady places.

A very important point is that oak has an incredible resistance to the pruning process, which must be carried out during the period of slow growth, so that the tree can quickly recover and not get sick.

Also, unlike what happens with other types of trees, knowing how to prune an oak tree You can practice any type of pruning, even a sharp rejuvenation is highly recommended when the tree is too old or when any part of it is in a strong wear.

Oak pruning

As with many plants, pruning is a very important factor for the proper development and growth of oak trees, so you should know how to prune oak , as well as all the necessary tools for the process, the correct trimming time and other aspects that must be considered when performing it.

For oak, pruning is an essential condition for its growth and obtaining a favorable shade, as well as a significant yield of fruits that serve as food for animals in the environment.

One of the most important points is that pruning has a direct effect on the oak as it is in its early stages of development, a process that can give long-term results as it ensures that all parts of the plant are properly aerated. and gives it a beautiful appearance from the crown to the base of the foliage.

The first time an oak tree is pruned with the main aim of building up the structure of the plant and providing it with a good basis for growth as it is in its early stage of development.

On the other hand, when the plant is 4 years old from the time of planting, pruning is carried out mainly for the purpose of clearing it and freeing it from any type of parasites, dry and old branches. It also helps to ensure good ventilation inside the plant and lighting of all parts of the plant.

What time of year is oak pruned?

A very important aspect to consider is the specified point at which the pruning process should be carried out, as it is well known that with this type of plant, if exposed to extreme climatic conditions after pruning, it can be harmful. to their development.

This is why the oak must be pruned at crucial times when its progressive development slows down a little, i.e. at the end of the cold season or at the beginning of spring, so that the plant is not too exposed to cold and that wounds can heal faster by the time they restart their stage development.

Particular care must be taken during the oak pruning season, as if this process is delayed and carried out at a time when the plant is in the best phase of development, it can suffer a significant loss of nutrients.

pruning tools

Oak is a tree that can grow to enormous heights and pruning usually requires a variety of tools to do it the best way.

It is necessary to limit the importance that all instruments are pre-disinfected with a suitable product for this type of instrument and, if possible, the disinfection process is also carried out after use.

This prevents any transmission of bacteria, fungi and other infectious agents that could endanger the health of this and other plant species on which the pruning tools will be used.

The tools to be used are as follows:

  • Pruning shears or small saw : This tool will be used to cut branches between 1 and 5 centimeters.
  • electric or hand saw : This will be used for large branches that cannot be cut with the first tool.
  • ladder : Specially designed for very tall oaks whose top branches need pruning.
  • Healing Paste : Used on newly cut plants to help close wounds and protect the plant from any type of infection.
  • Safety items : Items such as gloves, goggles and boots used to provide protection to the arborist.

How to cut oak?

Many people think that depending on the type of plant, the pruning process will always be the same, but the truth is that there are different types of pruning for each stage of plant growth.

That's why the first step in pruning is to make sure you know the age of the plant, depending on this information the pruning process will be different. Considering also that all plants age differently, influenced by vegetation characteristics, Soil types and the environment that surrounds them.

How to prune a young oak?

An oak can stop being young when it is over 6-10 years old, this is, as we have already said, an aspect that can depend on the environment in which it is planted. At this point, pruning the tree helps establish the growth structure.

The process that is followed in these types of pruning is usually the same, which we will show step by step below:

  1. First of all, you need to get rid of branches that are clearly in poor condition because they are dry or look weak.
  2. Some branches will be longer than others, and to make the tree look more aesthetically pleasing, they are cut to the same height as the others.
  3. Branches closer to the ground are cut off and the trunk is left clean.
  4. Ideally also remove the shoots to prevent new growth at the bottom.

It should be noted that although the oak pruning process is very similar, the truth is that they are performed for different purposes and some of the steps are not the same.

Form pruning

Its purpose is to establish the tree's growth regime, fix its structure and direct its development. The most important recommendation is to ensure that this pruning is done at the right time of the year when the tree's growth is at rest and has enough time to heal its wounds before any frost arrives.

At the first formation pruning, all branches are pruned to stimulate the growth of the tree. Now, for the second time, the main branches are lowered and the lower part of the trunk is cleaned, and the third time the main branches are lowered again and the branches remaining in the crown are removed.

Fruiting pruning

At this point, the main branches on which the rest of the tree will be attached are selected, they should be as straight as possible, with the intention that it will not fall under weight in the future, in addition, suction cups are excluded from these base stems. Secondary branches from which the fruit crop will be produced are also determined.

How to prune mature oak?

Doing a pruning process on an old oak tree allows it to keep the shape it has developed in, in addition to clearing the center of the tree, where many branches tend to accumulate after the tree has grown large, due to the fact that access to this space becomes more inaccessible.

By being able to get rid of extra branches inside the tree, air can flow through all spaces much better and sunlight can reach all parts of the plant much easier.


This is a pruning consisting of a series of steps that must be followed to improve the quality of the fruit and increase its quantity. The main task is to expand the light supply to a large part of the tree.

This process removes excess leaves and branches that are in the crown and center of the plant, in addition to secondary branches that do not produce as much fruit, so others will grow that will improve production.

The method for this pruning is as follows:

  1. The offspring that take up the most space on the branches are removed first, as this slows down growth and wastes excess energy. But you must let the plant save the weakest to protect the Tree main trunk.
  2. You must remove the branches that are at the bottom because they do not have access to as much sunlight as the others, and therefore the fruits they produce are not the best.
  3. Branches growing in the center should be cut crosswise with the rest, as such shoots interfere with the passage and growth of the rest.
  4. We must ensure that there is as much light as possible in the glass.
repair pruning

This is done on oaks that are already productive for many years and are starting to show signs of decline such as reduced levels of productivity, loss of leaf color and size in addition to other symptoms. would be noticeable to any specialist.

It should be noted that this type of pruning can be done in two different ways, the first being the quick way of removing all of the tree's foliage and leaving only the trunk with the most important branches, so the foliage will come back to grow again.

On the other hand, there is slow rejuvenation pruning where you start pruning from top to bottom, and this is a process divided into stages with a time interval of up to 3 years, with the goal of eliminating the main branches one at each stage.

Oak pruning tips

Plant pruning is always done with the aim of developing them in the best possible way so that they grow healthy, strong and optimize the production of any type of fruit. Here are some tips you can apply now that you know how to prune oak :

  • It's best to lob the crown before any other, as this helps expose more parts of the tree to the sun.
  • Be aware that unhealthy branches can significantly slow down the growth of a tree.
  • For the best view of the tree, it is best not to let the branches grow asymmetrically, especially in the crown.