As with most fruit and nut trees, Walnuts benefit from some training via pruning, especially in their early years. As the trees mature, pruning is really only necessary to keep the tree healthy and in good shape. This should be done during the winter months when the tree is dormant. Read on to learn more about how to prune a walnut tree.
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How And When To Prune A Walnut Tree?
To develop a sound structure that is capable of supporting the heavy branches of a walnut tree laden with nuts, and to prevent them from breaking in the wind as the tree matures, pruning of your young tree is vital.
The idea is to develop a strong scaffold of branches that grow from the tree’s main trunk, often called a central leader.
For a tree that is being grown for nut production, the lowest branches want to begin at around four to five feet up the trunk. For a tree being grown for its wood. The lowest branches should start at around 14 to 15 feet from the ground.
If you’re growing walnut trees to provide shade then branches will want to start at around eight to ten feet from the ground.
While waiting for your young tree to attain enough height, you can cut back any branches that develop so they are around six to eight inches in length. The leaves they grow will photosynthesize and help the trunk to develop and thicken up.
If you remove all the growth too soon, the trunk won’t become thick and strong.
Allowing these branches to grow to their full length will rob energy from the tree, and this can again slow the trunk’s growth. It isn’t only the height you want to develop, thickness is of equal importance.
When your young tree is big enough to encourage the development of true scaffolding branches, the temporary branches can be pruned off.
It’s better for the tree if this is done before they reach a thickness of more than half an inch, as the tree will be able to heal the wound more easily than if the branch is allowed to grow any thicker.
When deciding which branches should be kept and which should be pruned off, look carefully at the tree and think about keeping the branches you retain going up on a spiral around the trunk of the tree.
All of these branches should grow outwards away from the trunk, and the angle between the branch and the trunk should not be too closed. Having a more open angle is beneficial, but the branch shouldn’t be angled more than around 70°.
Too many branches emerging from the same level of the trunk can weaken the tree. So ensure they are well spread out.
Branches that are above one another mean the higher branch will block light from the lower one.
Setting out a good basic structure while the tree is still young will be highly beneficial as it matures, so it really is well worth doing.
Once your basic shape has been established, in subsequent years you need only remove any branches that are broken, diseased, crossing over, or growing inwards.
If you notice any of the side branches growing taller than the main central leader (trunk), then shorten them to the next side branch they have growing from them.
The best time of year to tackle walnut tree pruning is in late winter, during the dormancy period and before the sap rises.
This lets you see the structure of the tree more clearly and any potential problems there are. It also prevents new spring growth from being cut, which may affect fruiting. It also helps reduce the amount the tree bleeds.
Tools needed for pruning include:
- Loppers
- Hand pruners
- Pruning saw
- Rubbing Alcohol for sterilization
- Safety equipment (gloves, hard hat, eye protection, sturdy clothing that covers your arms and legs)
Always ensure you sharpen and sterilize your tools before you start pruning. Use the appropriate tool for the size of the branch you are cutting as you don’t want to crush or tear the branch, but cut it cleanly.
Remember that the removal of larger boughs will cause the tree stress, and it won’t be able to seal the wound very easily. You will also need to apply a special sealing solution that prevents the wound from becoming infected, rather like dressing an open wound on a person or animal.
Try not to allow the area that you cut to tear as this can again cause infection to set in. Make sure all cuts are clean with no jagged areas.
Larger branches may require you to make a jump cut. This is done in three stages:
- Start by cutting from the underside of the branch, halfway through the bough where you want to remove it from the tree.
- Next, remove the end of the branch completely, so it becomes a lot lighter and less likely to cause it to rip when you finish the initial cut.
- Finally, finish the cut from the top collar where the branch joins the trunk.
It isn’t usually necessary to excessively prune a walnut tree once it matures. Any significant shaping should occur in the first few years. After that, you really only need to prune to keep the tree healthy and maintain a good growing habit with open branches that allow air and light to circulate.
How High Does A Walnut Tree Grow?
- Black Walnut – A black or American walnut tree (Juglans nigra) thrives in USDA hardiness zones 4 to 9 and can reach heights of around 100 to 120 feet. It produces an abundance of nuts, and the timber is an attractive and sought-after hardwood.
- English Walnut – The English or Persian walnut, which actually originates in China (Juglans regia) doesn’t grow as high as the black walnut, reaching around 40 to 60 feet. Its nuts are large, and the husks are not as thick as the black walnut. It grows best in zones 5 to 9.
- Butternut – Not to be confused with the squash. The Butternut (Juglans cinerea) used to be a common sight in North America, but canker disease has decimated its numbers. Like the English walnut, it grows to around 40 to 60 feet and prefers hardiness zones 3 to 7.
- Californian Black Walnut – Another native walnut species is the California black walnut (Juglans californica). This walnut type looks rather different from the others, as it is smaller growing ranging between 20 and 49 feet.
It often has a double leader, which grows from low down, making the tree look like it is two individual trees growing side by side.
The nuts from a California black walnut have a tough outer casing and are quite small. It grows best in zones 8 to 10 and won’t tolerate cold as well as other walnut types.
Can You Top A Black Walnut Tree?
If a walnut tree is very malformed or something has happened, that means the central leader has broken off, you may need to take fairly drastic action if you want to save the tree.
Providing the point at which the problem begins is a branch or central leader not larger than 2 inches in diameter, you can cut the tree back at this point and allow it to re-establish. If however, the diameter is greater than 2 inches, even greater action is required, and the stem should be cut down to the ground.
Try to make the cut at a 45-degree angle just above a bud where possible. The bud should be facing upwards, away from any other branches that still remain.
Most of the side branches below the cut will need to be reduced in length. This is because they will start competing for dominance over the new central leader you are trying to get established.
It’s important to allow some branches to remain so they can leaf out, as this provides energy to the tree and helps it to recover and grow.
The following year you can remove the smaller unwanted branches and continue to do this each year until the tree is fully recovered.
Conclusion
Once they have been shaped correctly and become established after the first 3 to 5 years of growth, only a little light pruning will be required each year to maintain your walnut tree.
This is really only necessary in order to retain a good shape and to remove any problems such as dead, broken, diseased, crossed or inward growing branches.
It’s important to prune at the right time of year when the tree is completely dormant in winter, as pruning when it is growing will cause it to bleed a lot which can damage the tree.
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