Pistachio trees are pruned in much the same way as other fruit trees, although they don’t need to be pruned as hard. They don’t grow side branches easily, and it has been found that establishing the growth of a strong central leader rather than encouraging a U or V shape, results in a stronger tree less prone to breaking when laden with fruit. Read on to discover more about how to prune a pistachio tree.
What You'll Learn Today
How To Trim A Young Pistachio Tree?
Many fruit trees require quite significant pruning to maintain a good shape and encourage fruiting. This is not so true with pistachio trees.
Despite this, similar pruning rules still apply. Young trees should be trained in their early years to establish a good shape.
The shape is important as it influences the quality and quantity of fruit production and builds a frame that is easy to harvest.
In the first year after grafting, the rootstock should have all the branches of its own variety removed completely, these are the branches that are growing out of the root stock. Leave only the grafted branch (scion) in place.
First Year
The scion should be cut back to a height of 40 inches from where it joins the rootstock. This promotes branching and encourages thickening of the branches.
Second Year
In the second year, the strongest most vertical branch, usually the scion, should be chosen as the central leader and tipped (have the end cut off) but only if it has put on growth of 15 inches or more.
Secondary branches should be cut back further so they are shorter than the central leader. Ensure you tip them where there is an outward facing bud to encourage the development of an open canopy.
It isn’t necessary to remove secondary branches at this time because they will help develop the strength of the tree with the nutrients produced by their leaves.
Any branches growing from the rootstock can also be left for the summer months to leaf up, as this helps feed the tree and thicken the trunk.
Subsequent Years
In later years, any secondary and tertiary branches that are less desirable (angle less than 70° to the central leader or secondary branches) may be removed once the tree is more established.
Also, take out any that are crossing other branches or working to close the open canopy shape.
All branches coming from the root stock can be removed.
For the first five years, continue to develop the central leader and prevent any secondary branches from becoming too strong by giving them a light prune twice a year.
Older Trees
After the basic skeleton has been created, and an open crown shape is achieved, only light pruning should be given.
Always ensure any cuts you make when pruning are completely clean. Don’t leave any jagged splintered wood.
Tools
The tools you use should be disinfected with surgical spirit before use, especially after cutting out any diseased wood, and when moving between trees.
Use the proper tools for the job:
- Secateurs for small branches of ½ an inch wide or less
- Loppers for branches up to 1 ½ inches wide
- A Saw for branches over 1 ½ inches wide
In this video, you will see how to correctly prune your pistachio trees in the first two years of growth:
What Time Of Year Do You Prune Pistachio Trees?
Pistachio trees should be pruned in late winter or early spring while they are still dormant. They can also receive light pruning in summer to remove young shoots over 30 inches to avoid bending but only if necessary.
Pruning Mature Pistachio Trees
- Older trees – These are pruned to ensure they retain an open shape, and so the inner branches can receive both sunlight and air circulation.
- Continual pruning – Dead, broken, diseased, or weak branches, and any suckers, should also be removed throughout the tree’s life.
- Less is more – Overall mature pistachio tree pruning should be as minimal as possible. Don’t be tempted to reduce the crown by more than 30% as this is where the tree fruits, and doing so can cause the tree to produce more closed nuts.
- Sick trees – If the tree is badly diseased or weak, then it may require a more severe prune, but be aware that it will affect nut production for a couple of years as pistachios produce fruit on one-year-old wood.
- Maintaining an open canopy – When pruning, always cut just above an outward-facing bud to maintain an open canopy. This allows for sunlight penetration which is necessary for blower bud formation and the ripening of fruits.
- Mature trees – Trees that are15 years and older, bear fruit in the upper part of the canopy. Pruning year-old wood back too hard will reduce fruiting. Only cut the year-old wood back to 20 inches, not more.
- Male pruning – Once you know the sex of your pistachio trees, you won’t need to prune the males. They are allowed to grow more freely as they will be taller than the females, which helps pollination.
- Maintenance – Only essential maintenance pruning of males is required, or if they start to encroach on the growth of female trees, they can be cut back.
How To Prune A Pistachio Tree With Roundup Damage?
Glyphosate herbicides – “Roundup” can cause significant tree damage. The chemical may be absorbed into the roots, which prevent the uptake of micronutrients such as zinc, manganese, boron, and iron, micronutrients which help prevent the tree from becoming diseased.
If the damage is only light and very occasional, then usually the tree will recover on its own. If you think that some was sprayed onto the tree by accident, try washing it off using a strong water jet as fast as possible.
Small, young trees can be washed off with dish soap and water then thoroughly rinsed.
Once caused, there is no way of reversing damage by herbicides. Damaged plant tissue will not rejuvenate, and any branches or leaves affected should be pruned off, so new growth is initiated.
Older trees are usually more able to tolerate herbicides than young or newly planted ones. If you wish to use a herbicide, you can protect the bark and foliage of a young tree from spray drift blown in the wind by covering it in plastic, or for larger trees by wrapping the trunk in plastic or paper.
Young pistachio trees are easily damaged by herbicides, and good spraying practices should be used to prevent or at least minimize the risk.
When spraying, direct the spray to the base of the tree and avoid any contact with the foliage or young wood. Don’t spray on a windy day and use spray nozzles which reduce drift.
There is a wide range of herbicides available, some of which are applied before the weeds come up and some after.
How Tall Do Pistachio Trees Grow?
The pistachio tree is slow-growing, and long-lived. It grows seasonally through spring and summer, and its growth rate is dependent on the age of the tree, its health, and the growing conditions.
The cultivar of the tree, soil, water, sunshine, and so on all have a bearing on how well the tree grows throughout its life. Most pistachio trees reach a height of between 20 and 33 feet.
For a tree to begin producing nuts, it needs to be mature enough. For it to reach maximum harvest quantities, the tree usually needs to be around 15 years old, and it can continue to fruit, usually every other year, as they are alternate-bearing, until it is well over 100 years old, although 40 years is the expectation for commercial orchards.
The trees are able to live for more than 300 years, if conditions are favorable.
Conclusion
Pistachio trees require careful pruning in their early years to establish:
- A strong central leader
- A thick trunk
- A strong root system
- An open canopy with widely spaced branches, allowing ease of access for harvesting and for air and light to penetrate around the tree.
It is easier to prevent damage from herbicides than to treat it once the damage has been done. If damage is only light, the tree will usually heal itself in time, but too much damage will cause the tree to die.
Learn more about pistachio trees, their products, or a wide range of other topics from our website.
