Pruning english walnut trees

Walnut Tree Pruning Tips

A walnut tree makes a great addition to any yard. They do not require a lot of work once they have gotten started and established. The first few years are full of care and maintenance of the young tree though. They do require regular pruning. If left to grow as it likes, a walnut tree can become quite massive and full of limbs. Pruning your walnut tree will keep it healthy and full of fruit for many, many years. Here are a few things to know about pruning your walnut tree.

1. Pruning Is Needed

As a walnut tree is growing, it will need to be pruned in order to train it and shape it to the way you want. Pruning is basically taking off damaged and dead branches that are not growing and are too weak to handle any added growth. Pruning, though, keeps the tree invigorated. As you take off some of the new limbs, old growth, and dead limbs, the tree can release that energy into different parts of the tree. This will cause an abundance of nuts, revitalized growth in the direction you want, and better resistance to disease.

2. When Should You Prune Your Walnut Tree?

There are several different times when pruning is necessary, the first being at planting. When you first plant your walnut tree you should cut back the top of the tree until it is a dormant bud. This bud will then begin to be the main trunk of the tree. For the first couple of years you should continue to prune the tree back to this main trunk to let it grow taller. As it gets taller you should then remove any branches that you do not want to be the main skeleton of the tree.

After the first five years, you should have a wonderfully-shaped tree with a strong main trunk and skeleton branches that fill out the tree. Prune it very heavily every three years after that to thin it out and create new upward growth.

3. How to Prune

One of the biggest tips for pruning your walnut tree is to cut off the limbs when they are very small. This will make the wounds in the tree small and less susceptible to insects. If you are removing larger branches, then you should leave the base of the limb so that it will scab over easier. Taking off the top of the tree, or the top of limbs, requires that you cut it back to the dormant bud.

4. What Is Pruned?

The main focus of the pruning should always be the shape of the tree. Always remove any branches that are drooping towards the ground or do not add to the overall structure and shape. Any weak branches that you see, and dead branches should also be removed. Use your discretion of what else to take off. You should look at the canopy and remove any limbs, offshoots, or small stems that will not add to the structure.

Pruning your walnut tree will help it grow healthier over time and produce much better nuts. Use these tips to help you better prune your walnut tree.

How to prune a English walnut tree

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Because Walnut trees are susceptible to blight it is recommended major pruning be done during the dormant period. Dead wood can be removed at any time and minor cleanup to open the canopy can be done when there is a forecast for no rain for a period of at least a week after the pruning.

Older walnut trees need pruning every 2 to 3 years and if this tree has not be pruned for a long period of time the process of pruning should be a multiyear process. A good place to start is opening the inside of the tree and eliminating crossing branches. Larger trees may need the use of professional equipment to access the taller branches.A good rule of thumb is to not remove more than 20% of foliage in one year.

Walnuts are a challenge to grow in the Northwest and most commercial growers have given up. The small nuts can be caused by a lack of boron in the soil or by the fact that the tree is a variety that produces flowers when conditions are not favorable to pollination.

The good news is since walnuts were once a large crop in the Northwest, there are plenty of articles on growing walnuts. See these sites for more information:

Growing tree fruits and nuts

Growing walnuts in the PNW

Here is a link for more information on pruning.

Walnut Trees

How to Prune Walnut Trees

In addition to providing nuts, walnut trees are drought-resistant and provide shade. You only need to prune them occasionally to remove excess branches and keep the walnut tree healthy. When pruning a walnut tree, keep in mind that the trees can be grown with a central leader (which helps them grow large), or you can keep them smaller by removing the leader. The most common method is to keep the central leader.

Avoid pruning from late winter to early spring, as the sap will seep out a lot during these times. The best time to prune is from half-way through the summer to early fall.

Select the largest, most dominant trunk as a leader. The leader brings the nutrients up from the ground to ensure the other branches grow straight out.

Use lopping shears (for large branches) and pruning shears for smaller branches to remove side branches. Cut along the lines where branches join each other or connect to the trunk. Along the leader trunk, remove the lower branches when the walnut tree is young. Keep larger branches close to the leader, as well as the smaller branches growing from them. Cut out the mediun-sized branches from all areas.

Repeat this method to prune the walnut tree during the first few years of growth until the tree reaches 17 feet.

How to Identify an English Walnut Tree

Study the overall shape to the tree. English walnut trees’ canopies have a spreading, rounded shape.

Look at the shape of the leaves to identify an English walnut tree. The leaves are oval and grow together in groups of five to nine alternating leaflets on a single stem.

Identify the English walnut tree by its leaves’ size and margins. The leaves have smooth edges and are 5 to 9 inches long.

Spot English walnut trees by studying the fruits. The walnuts grow in green husks, which split open and release the nut when they ripen. Inside the husk, the walnut’s shell is lumpy with a vertical seam along the length of the slightly ovular, light brown exterior.

English Walnut Tree Diseases

Leaf blotch creates brown spots on the nuts and leaves, causing them to fall from the tree. Root rot affects the roots, causing the tree to become stunted and the lower leaves to turn yellow and discolored.

Fungal Treatment

Leaf blotch is treated by removing and destroying infected leaves and nuts and applying a fungicide that contains hydrated lime and copper sulfate. Removing the trees is the only solution to root rot, as the roots are destroyed and the tree will never recover.

Bacterial Disease

Walnut blight produces black spots on the leaves with spots and holes in the nuts. Crown gall creates a gall or ball on the main stem of the tree.

Bacterial Treatment

Walnut blight is treated by pruning and destroying affected areas and applying powdered copper sulfate. Treat crown gall by removing young trees and painting the gall on older trees with a commercially purchased gall treatment made from a natural strain of Agrobacterium radiobacter. This bacteria is a close relative to the crown gall bacteria and blocks it from entering the tree.

Viral Disease

Blackline is a disease that kills the tops of the trees and causes shoots to grow from the roots. The virus spreads quickly as it is carried by infected grafts, seed and pollen.

Viral Treatment

Complete removal of the tree top is required to control blackline; there is no treatment. Start a new canopy by developing several suckers on the tree.

Facts About Walnut Trees

The black walnut has the largest geographical distribution of any walnut in America, growing in most of the central eastern portion of the nation. Another type, the butternut tree, exists in the northeastern section of the country.


In terms of size, the black walnut is the tallest species of walnut, with some growing to be 100 feet high. The butternut averages between 50 and 60 feet tall while western species such as the Arizona walnut and little walnut are smaller at about 20 feet.


Walnut leaves fall off each year and are alternate on the twigs and compound. This means that there is a leaf at each individual node on the branch and the many separate leaflets on one stem comprise each individual leaf.


The nut of the black walnut tree consists of a kernel encompassed by a hard round shell which itself has a tough husk surrounding it. This husk turns from green to yellow-black as the nut ripens.


The Native Americans would boil kernels of the butternut tree to extract the butter-like oil for culinary purposes.

What Is the Lifespan of Walnut Trees?

The walnut tree has an average lifespan of 80 years. However, some walnut trees have a lifespan several times longer than the average human lifespan.

How to Compost English Walnut Leaves

Chop the leaves into small pieces by running over them with a mower equipped with a mulching blade or by raking them into piles and chopping them with a hoe. The leaves will compost more quickly if broken into small pieces.

Layer the leaves in the compost pile with other organic matter, such as kitchen scraps or grass clippings. Leaves are naturally high in carbon, which composts slowly. Layering in high-nitrogen matter such as grass and vegetable peelings will speed composition and increase the temperature of the compost pile, which will break down the juglone more quickly.

Water the compost pile to keep it moist but not soggy. Moisture encourages the growth of organisms that speed decomposition and hasten the transformation of the leaves to healthy compost.

Turn the compost pile regularly to aerate the contents. This also hastens decomposition.

Facts About English Walnut Trees

English walnut trees grow between 40 and 60 feet tall with an equal spread. They have smooth, gray bark, a spreading, rounded crown and pinnately compound leaves, which means that 5 to 7 pairs of leaflets grow opposite one another on a leaf stem. The male trees produce catkins, or flower clusters that have no petals, while females produce short, spiky flowers that are replaced by edible nuts.


English walnut trees grow in United States Department of Agriculture plant hardiness zones 3 through 7, which includes cities such as Tomahawk, Wis., Columbia, Mo., and Oklahoma City, Okla. They prefer well-drained, nutrient-rich soil and full sunlight. English walnut trees are susceptible to attack from caterpillars and webworms. They are also susceptible to anthracnose, leaf spot and root rot, among other diseases.


English walnut roots produce toxic chemicals called juglones that damage or kill many plant species such as tomatoes, potatoes, peonies and azaleas, among others. The nuts, which mature in the fall, can be messy. The trees have a deep taproot that makes transplanting difficult. Plants For A Future recommends only pruning trees when they are dormant; they bleed profuse amounts of resin and become weak from pruning injuries.

How Often Do Walnut Trees Get Nuts on Them?

Jupiterimages/ Images

Time of Year

In the spring, small, green husks, containing walnuts emerge from small, inconspicuous flowers on the tips of walnut tree branches. Throughout the summer these husks continuously expand around the developing walnuts. Harvest season for nuts occurs during the months of September or October, as the nuts fall from the tree.


At best, trees produce nut yields once a year during the fall. However, many walnut tree cultivars, particularly outside of commercial production, are prone to alternate bearing of nuts. This is characterized by one year of intense over-production followed by a year of little to no nuts.

Other Considerations

Total annual nut yield is only one of the considerations for cultivar selection. Other important considerations include quality of nut yield and ease of cracking.

Can a Lilac Grow Near a Walnut Tree?

lilac image by Henryk Olszewski from

Black and Persian walnuts release the chemical juglone into the surrounding soil as a defense against insects and fungi. Lilacs planted near them–or several other walnut family trees–may develop walnut wilt or stunted growth in response to the juglone.

Trimming A Walnut Tree: How To Prune Walnut Trees Properly

Walnut tree pruning is important for the tree’s health, structure and productivity. Walnut trees (Juglans spp.) make very nice shade trees, are excellent timber specimens, and also produce delicious nuts for eating by humans, birds and squirrels alike. Keep reading to learn how to prune a walnut tree.

Pruning Walnut Trees

Trimming a walnut tree properly is vital to your investment. When you are developing a young walnut tree, you are developing its structure. You need to decide how high up you want the scaffold (side) branches on the trunk.

  • For harvesting nuts, you might start your scaffold branches as low as 4 ½ feet.
  • For a shade tree, you might start your side branches at 6-8 feet in the air.

When your new walnut tree is too short to start developing scaffold branches, cut back any little side branches to 6 inches long. Leaving these short branches for a few years encourages trunk strength and vitality, yet doesn’t rob too much energy from the trunk.

Once your tree is large enough to start guiding the long-term scaffold branches, you can start cutting off the little stub branches below. It is best to remove the little stub branches before they grow over ½ inch in diameter. The tree can seal off pruning wounds much more easily when they are smaller.

Walnut tree pruning requires careful observation and judgement. Develop potential scaffold branches that are evenly spaced around the trunk. Trimming a walnut tree also involves annually removing damaged branches, crossed-over or rubbing branches, and any branches that want to bend backward toward the center rather than reach outward.

Additionally, walnut tree pruning involves making sure that all side branches remain subservient or lower than the height of the central leader. In these situations, simply shorten the competitive side branches back to a tertiary side branch.

What’s the Best Time to Prune Walnut Trees?

The best time to prune walnut trees is the later end of the dormant season when the trees are still out of leaf. This way you can easily see the form of the tree and yet you are not cutting away any new growth that appears in spring.

Make sure you clean and sterilize your hand pruners and pruning saw beforehand so you don’t spread disease. Sharpened tools ensure clean cuts too. Trimming a walnut tree should not involve ripping or tearing the bark from dull tools.

If you need to remove a larger branch, perform a jump cut to prevent the weight of the branch from tearing away the outer bark of the trunk as the branch separates from the tree. Jump cutting involves three steps.

  • First, cut half way through the branch from the underside just outside the branch collar.
  • After that, you want to completely cut off the branch further out (1 to 3 feet) on the limb.
  • Finally, you will cut the remaining stub just outside the branch collar.

Walnut tree pruning is an annual event even when the tree is mature. Investing some time and energy into proper walnut tree pruning will yield a tree that is strong, productive and attractive to view.

A walnut is the nut of any tree of the genus Juglans (Family Juglandaceae), particularly the Persian or English walnut, Juglans regia. A walnut is the edible seed of a drupe, and thus not a true botanical nut. It is commonly consumed as a nut. There are several species within this family, perhaps the most widespread and popular are English walnut and black walnut. In this article we will cover everything about how and when to prune a walnut, in addition we will analyze the features of English walnut and black walnut pruning.

If you read to the end you will learn the best techniques for proper pruning, the right time to trim and the tools to do it. The article has no waste, I assure you. 😉

Note: Please note that the advice given here is general, this blog is consulted from many countries in the world, with totally different characteristics, what not all tips will be adapted in the same way in all cases. Once you finish reading the article it will be necessary to analyze all the information and apply what you have learned in the best way. If you have any questions, remember that you can contact us to make your inquiries.

Table of Contents

1. Interesting fats about walnuts trees

Before entering the main topic of this post, prune the walnuts, I leave some interesting facts about this tree. I bet what you want, you do not know one or several of them. 😉

  • Walnut is known as “karyon” in Greek language, which means “head”. Name originates from the fact that walnut shell looks like a skull which protects brain-like kernel located beneath it.
  • The nuts that are not yet ripe contain cyanide, which is why it is not advisable to consume them. This is, also, the reason why it is repeatedly recommended not to sleep under the shade of the walnut tree. There are, in this regard, multiple proverbs.
  • Hundreds of healing and medical properties have been granted to the walnut, although not all are true or proven.

Walnut tree

  • Although its goodness in the cardiovascular system seems to be demonstrated, its great contribution of calories (fats and carbohydrates) must be taken into account. You should, therefore, limit your consumption if you do not want to gain weight at the same time.
  • Always, from very remote times, the nut has been associated with good health and memory.
  • Walnut shells are used in the production of grit paper, glues, plastics and cleaning products. Walnut wood is used for the manufacture of flooring, furniture, musical instruments, panels, veneers and gunstocks.

  • In ancient Rome, if the groom threw nuts to the crowd, he meant that he would be faithful to only one woman.
  • In times when tobacco was scarce, walnut leaves, once dried and chopped, were used as their substitute.

Until here some of the curiosities that I have considered more interesting about the walnut. Now let’s do our thing, pruning. 😉

2. Tools needed to prune or trim a walnut tree

As with all fruits, there are several tools you will need to carry out your pruning or trimming. Each of them appropriate for different cases depending on the age of the pomegranate, the time of year, type of pruning etc.

  • Pruning shears.
  • Handsaw
  • Chainsaw.
  • Ladder or scaffolding.
  • Basic safety elements such as helmet and gloves.

Keep in mind that you must disinfect all cutting tools before pruning the walnut tree. This will help to avoid transmitting diseases, you will have to do it before you start pruning and every time you change plants.

2.1 Needed care of pruning tools

If you want to extend the useful life of your pruning tools there are some basic care.

  • Use the right tool for a job and avoid twisting or straining it.
  • Clean and oil tools regularly by wiping an oily cloth on blades and other surfaces.
  • Keep cutting edges sharp by regularly using an oilstone.
  • Wooden handles should be varnished or regularly treated with linseed oil to keep them from cracking or splintering.

Carry out the previous care on a regular basis and you will be saving good money on tools. 🙂

You may also be interested in knowing about pruning:

  • Pomegranate
  • Apricot
  • Avocado

3. Pruning a walnut tree – How to prune

The pruning of the walnut can be divided into three, depending on the age of the garden and the objective that is sought with pruning. These are training pruning, production pruning, corrective pruning and rejuvenetion pruning.

  • Training pruning: this pruning is done from the plantation until the sixth to seventh year, and aims to drive the plant and generate a productive structure that is efficient as quickly as possible.
  • Production pruning: this pruning is done since the productive structure is formed, in some cases from the sixth year onwards and aims to keep the garden well lit to achieve high production and not lose productive centers in the tree for lack of light.
  • Corrective pruning: this pruning aims to correct problems that reduce the productive potential of the garden and aims to modify the structure as soon as possible to increase the productive efficiency of the tree. The main problems are the shade and the concentration of main branches in the lower part of the tree, which generates an insufficient height of the productive structure.
  • Pruning of renewal: when the walnut trees reach their age (about 10 years old) they need to renew their branches, this is achieved with a more severe pruning than the previous ones, which is known as pruning of renewal.

Since each of the previous prunings are very different, both in objectives and in techniques, we will then separately develop each of them.

3.1 Training pruning – Prune young walnut trees

There are numerous factors that influence the pruning of formation of a walnut tree, among them we can mention:}

  • Objective of the plant: the most determining factor when forming a walnut tree is determined by the purpose for which we plant this tree. The most common is for the production of nuts but it is also widely used for wood production.
  • Variety: depending on the characteristics of the variety of walnut that is being used, the pruning of formation varies.
  • Vigor of the trees: If there is a lot of vigor it is necessary to control the lack of light in the center of the plant from the third year, if the vigor is too low it is necessary to make cuts to induce vigorous growths.
  • Wind: in places where the wind is a serious problem, it is necessary to take certain precautions. The trunk should not be cleaned more than what is needed for good weed control, to achieve a more compact tree with a more resistant trunk, which considerably reduces the problems with the wind. You also have to consider a good tutor to achieve a well-formed plant.
  • Light: when the walnut is being formed, it is necessary to consider the best possible use of light, which is essential for good production. For this reason, the structure must be efficient. A maximum height must be considered so that the shade of one tree does not harm the production of the other, the height of the plant must not exceed 80% of the distance between rows, also within the same tree it is necessary to achieve a good distribution of the branches so they do not shadow each other.

Since this walnut pruning is governed by many factors it is difficult to cover all the possibilities in a single article. In the same way we can summarize the training pruning in two types; Training pruning for nut production or walnut formation for wood production.

3.1.1 Training pruning for nut production

The pruning of a walnut to produce nuts begins in the plantation. The shape to which this plant best adapts is that of the one developed with a central axis.

It consists of forming a main trunk – the axis – that grows in height as the tree develops, and some main branches of horizontal growth that are selected along the trunk so that there is space between them – but not too much – and that they are oriented alternately in all directions, to form a consistent cup.

Walnut formation with central axis

For this, in summer the most vertical and most vigorous growth bud is chosen, and a tutor is tied to keep it straight. The other shoots are blunted since they will then be cut in winter. In the following summer, the branches that have not been selected as main ones are highlighted, and those that still are, grow disproportionately. Those that compete with the axis in vertical growth will be eliminated.

While the formation lasts, it will be necessary to cut the axis in winter about 50 cm above the last main branches, to form a new floor of branches below this point, which will have to be selected again to leave the best orientations and eliminate those that can compete with the axis.

3.1.2 Training pruning for wood production

In the case of the formation of a walnut to produce wood what we are looking for is to develop a main trunk as straight and without knots as possible. For this, a dynamic or balanced pruning scheme can be developed. Dynamic training pruning

Dynamic pruning in the formation of walnut is recommended in sheltered and fertile farms. It does not set pruning height. The first two years all branches are pruned.

Dynamic training pruning

The following years the lower branches are eliminated, hairpins are corrected and the cup is balanced horizontally. In 7 years you can reach 3 m free of branches. Balanced training pruning

This second trained pruning called as balanced is recommended in most farms. In this case, a pruning height (H) is set according to the quality of the farm (between 3 and 6 m). Until the tree reaches height H, it is especially monitored that there are no forks or branches that can compete with the main trunk for dominance.

Balanced training pruning

The branches of the year that have acute insertion are eliminated and compete with the terminal guide, in particular the forks. Also the branches of a year or more that approach 2.5 – 3 cm or that present acute insertion. Finally you can cut the branches that can reach this thickness shortly.

After reaching height H, the objective is to progressively clean the trunk of branches. To avoid breakage, it is convenient that the tree does not open immediately after reaching H.

3.2 Production pruning

With this pruning of the walnut tree should be kept illuminated throughout its structure. It is necessary to eliminate the growth of new times that generate problems, renew the production centers to produce the pieces of good quality and it is also necessary to maintain a structure that allows the realization of the work of cultivation in the garden. For this, we recommend that you perform the following activities, ordered by their priority.

  • Light inside the tree: in order to keep the tree well lit, it is recommended to allow light to enter from the north, eliminating the branches that obstruct the entry of light, in the form of a triangle towards the center of the plant.

Light inside the walnut tree

  • Elimination of badly located branches: It is necessary to eliminate branches that are close together where shading occurs, to maintain a good use of light.
  • Elimination of badly located pacifiers: It is necessary to eliminate every year the suckers that are inclined towards the center of the plant and also those that are in an upright position, because this position produces a greater shade and with the weight they can be tilted towards the center of the plant.
  • Light between rows: to achieve this goal, it is necessary to define a minimum distance between the rows free of branches and cut branches every year that exceed that limit.
  • Renovation of production centers: when a walnut is pruned it is necessary to review the branches year after year. In the case that it is observed that the greater proportion of the darts are too short (<5 centimeters), it is convenient to eliminate the branch since the production is limited and the quality of the nuts is not good in relation to the caliber.

Taking the previous precautions during the production pruning of the walnut will ensure a higher quality of nuts for the harvest.

3.3 Corrective pruning of the walnut

In pruning correction there are several examples. We will mention the most important ones and their alternative of correction.

3.3.1 Ambush

This problem occurs in plantations that are left without light inside. This has as a consequence that the production moves to the periphery and the roof of the orchard, decreasing notably the production of nuts per hectare.

The solution is to let the light into the garden, the first step is to open the inter row and then the following year it is necessary to facilitate the entry of the light in the north-west zone of the tree and in a third year to select the branches that are badly located. The solution to this problem takes 3 years.

3.3.2 Low altitude garden

This problem is generated when in the formation too many main branches are left in the lower part of the tree (5 to 6 branches between 1.6 to 2.6 meters), which generates a low tree, where the central axis has smaller diameter than the basal branches.

You will imagine that we will give solution with a pruning in the walnut. With this pruning we will have to transfer the vigor to the top of the tree, and this is done by removing one to two main branches from the bottom of the tree per year until leaving two to three at most between 1.6 and 2.6 meters. The diameters of the main branches must be less than 1/3 of the diameter of the central axis.

3.4 Pruning of renewal – Prune old walnut trees

After a certain age (about 10 years) the walnut will need to be renewed as its branches begin to be unproductive. When that happens it is the right time for a pruning of renovation in the walnut.

The pruning of renovation consists of eliminating the non-productive wood of the plant, with the aim of generating new production centers. This pruning could be carried out in a season, but this brings as a consequence a sudden fall in production. That is why it is recommended to make cuts in a staggered way during the successive seasons, lowering the thick branches, so that the yield does not fall sharply.

In the first year the lower branches are cut, the second the unproductive ones, and in the third year the upper ones, which generate excess shade. This prevents the production of the garden from going down a lot. What is eliminated the previous year is recovered in the following season.

4. When to prune walnut trees

The selection of the right time to prune a walnut comes from the hand with which it is a deciduous tree, meaning that it loses its leaves during the winter. Because of this, the ideal time to cut branches is winter.

When the walnut is at rest during the winter months there will be less loss of sap in the cuts, thus reducing the level of suffering of the same, allowing a faster recovery. In general, and as far as possible, it is to winter meditations when it is recommended to prune the walnut. If you prune very early you are more likely to acquire diseases through the cuts, and if we can very late there will be greater loss of wisdom and therefore energy.

So you know before you start pruning this plant, look at the calendar, if you’re in mid-winter, it’s time to work. 😉

5. Pruning black walnut trees

There are many questions about how to prune a black walnut tree. That is why I found it interesting to devote a small section to answering this query.

The pruning of a black walnut does not have great secrets, having to carry out the same pruning as in a common walnut tree. This is training pruning, production pruning, corrective pruning and renewal. If you follow the advice we have seen so far in this article, you will not have any problems carrying out this afternoon in your black walnut.

6. Pruning walnut trees – YouTube

As we always do in this blog we will finish this article with a video, although on this occasion I have selected more than one. In the first video we talk about the pruning of training in a walnut tree.

How to train Walnut Tree – toolsresources channel

In the second video you will see the mechanized pruning of walnuts.

Pruning walnuts trees – capitalagriculture channel

Well that has been all, I hope that it has been clear that I have seen them until now, how and when to carry out the pruning of a walnut tree, and that you have no doubts when you take your scissors and start trimming. 😉

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Source information:

Estrategia de poda en nogales –

Nogal para madera – Óscar Cisneros, Víctor Martínez, Gregorio Montero, Rafael Alonso, Antonio Turrientes, Javier Ligos, José Santana, Raúl Llorente y Eloy Vaquero.

Aspectos técnicos para la poda del nogal – Giovanni Lobos L., Ingeniero Agrónomo, INIA Intihuasi

Pruning Forest Trees

Carol B. Trokey and E.A. McGinnes, Jr.
School of Natural Resources

Pruning trees in the yard and in the forest can yield many benefits — if it is done correctly.

In a woodland or plantation, pruning helps maintain a central leader, repairs storm damage, or improves the chances of a clear bole to produce a higher grade of lumber or veneer.

In your yard, pruning shade trees controls the tree’s size or shape, removes undesirable branches, or reduces a hazard posed by dying or broken branches. Poorly formed branches in the unpruned shade tree can get weaker each year. It is also necessary to prune trees along power lines in both rural and urban settings to prevent damage during storms.

Trees in Christmas tree plantations are sheared to produce a tapered shape and dense foliage.

Whether in a forest setting or yard, start proper pruning early in the life of a tree and continue when necessary as the tree grows. In the forest setting, economics dictate that only the higher-value species, such as black walnut or possibly white oak, should be pruned in Missouri. A clear walnut bole, free of rot and damage, will bring a much higher price at the mill. Because of the thin foliage of black walnut, it is a poor self-pruner. Its natural pruning ability is further reduced in the plantation setting, where it is planted in wide spacing to promote diameter growth.

When to prune

All pruning is potentially harmful to a tree; prune so the resulting wound can close as easily as possible. At the time of planting, trees can be pruned to correct multiple leaders. Select one strong central stem and do not prune this stem or any twigs along the upper branches of the tree. Remove any other weakened or damaged branches. Always maintain at least two-thirds of the total tree height in living branches.

As a shade tree grows and total height increases, you can remove lower side branches. Do not prune all side branches in a vertical line in one year. If you start pruning early, tree-splitting may be avoided later because low, heavy branches often split during storms or when weighed down with snow and ice.

Trees do not “heal” in the sense of restoring cells at the site of injury or damage. Trees have the ability to compartmentalize, or form a barrier zone at the damaged area to help prevent disease infection. Prune properly to help this natural process occur as quickly as possible. Trees may be healthy but still have numerous infections walled off in pockets throughout the stem. The genetic makeup of some trees allows them to form this barrier zone tissue more easily than others.

The best time to prune live branches is during the dormant season — late winter or early spring before leaves form. These wounds heal most rapidly and sprouts from dormant buds are less likely to develop. If possible, avoid pruning at the time of leaf formation and leaf shedding. If sprouts do develop, remove them promptly. Remove diseased and dead branches any time you notice them.

Pruning guidelines

Much of the following information on pruning guidelines is based on the years of experience and extensive research of Dr. Alex L. Shigo, retired Chief Scientist on tree decay, Northeastern Forest Experiment Station, Durham, New Hampshire, and Dr. E. A. McGinnes, Jr., MU. They have conducted extensive studies on the effects of pruning black walnut. To produce walnut veneer and timber, prune in stages until a clear bole is reached. On a medium-quality site, black walnut should be pruned to 9 feet by about the 10th year and to 15 to 17 feet by the 16th year. That produces at least a clear 14 foot log at harvest. Your local forester from the Missouri Department of Conservation can give you more advice on black walnut management.

Follow these steps to help promote fast healing of your pruned trees, whether in the forest or yard:

  • Prune living branches as close as possible to the trunk, but do not cut behind the branch bark ridge. Each branch has a thick bark ridge separating it from the main stem (Figure 1).

Figure 1
Natural pruning steps include locating the branch bark ridge. Then find target A — the outside of the branch bark ridge — and target B, the swelling where the branch meets the branch collar. If B is hard to find, drop a line from point A. The angle from XAC equals the angle from XAB. Next, stub the branch to be cut. Finally, make a cut on line AB. (Drawing courtesy of the Missouri Department of Conservation.)

  • Do not use flush cuts. A large callus will have to form to help seal the wound. Branches that have been pruned correctly will have callus material completely encircling the wound rather than in a horseshoe or semicircular pattern.
  • Do not leave branch stubs. They will just have to decay and fall off.
  • If removing dead branches, do not cut into the collar that has formed at the base of the dead branch. The collar is the raised ring of protective tissue circling the branch and acts as a barrier to further decay.
  • Concentrate pruning on the smaller limbs to promote faster healing. Cut larger branches using a three-step method so the branch’s weight will not cause the branch to break and tear the bark below the limb. Relieve the major weight of the branch by using two cuts and then cut at an angle near the branch bark ridge (Figure 1). If the job looks too large or dangerous, hire a professional.
  • Do not top trees. Even if upper branches are damaged in a storm, make repairs by cutting the branch at about a 45-degree angle or along the branch bark ridge. Remove broken tops and branches as soon as possible after injury.
  • Wound dressings have not been proven to increase the rate of wound healing, so use them only for cosmetic reasons.
  • Use the proper tools for pruning. Use chain saws only to remove the larger portion of storm damaged limbs; otherwise use smaller pruning tools that are more easily controlled. Keep pruning tools clean and sharp. Diseases can be spread by tools from tree to tree after you cut an infected plant. To sterilize pruning tools, clean them in a mixture of one part household bleach to 10 parts water. If branches are too high to reach, use a pole saw or ladder.
  • Cavities require special treatment and should be handled by a professional arborist. Remove only decayed wood that easily comes out of the cavity. Do not cut into the hard rim of tissue surrounding the cavity or decay will spread.

Care after pruning

Maintain the vigor of your shade trees before and after pruning by watering during dry spells, fertilizing when necessary (usually from late September through early April), and avoiding unnecessary wounding. Injury at the tree base can occur if you hit it with your lawn mower.

In the forest setting, practice good timber management by cutting out less desirable and poorly formed species to benefit your more valuable trees. A well-conceived plan can help your trees stay “fit” for many years.

For free technical advice on forest management, contact a forester from the Missouri Department of Conservation. Additional information can also be obtained through local MU Extension centers.

For more detailed information on tree health and biology, contact Dr. Alex L. Shigo, Shigo and Tree Associates, 4 Denbow Road Durham, New Hampshire 03824.

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