Drawing of Open Vase Fruit Tree Pruning

By Xander Rose

When a young fruit tree is being established after planting in its lifetime location some pruning may be involved to get the tree into proper shape. Even if an elaborate pruning system like espalier (saving that for a possible later blog post!) isn't to be developed, a fruit tree will require some pruning in its first few years to develop a manageable form. Certainly, if the aim is to have a reduced height (such as for a pedestrian tree within reach), then pruning is key in the early years. Of course, no matter the strategy, dead wood or damaged branches should always be pruned out cleanly.

Two common, uncomplicated pruning strategies for developing a fruit tree are the central leader and the open center, both of which can be modified and varied.

I have worked on both central leader and open center pruned trees in the orchards at Raintree and am working to develop trees in both these ways in my home orchard. Trees on dwarfing or semi-dwarfing rootstocks are ideally suited to be pruned in the central leader or open center styles. One of the most important benefits of grafted trees is the height control of dwarfing or semi-dwarfing rootstocks. Shorter trees make for easier and safer harvesting, pruning, and other orchards tasks. It's nice to only need short ladders, or no ladder at all!

If my fruit tree is on dwarfing rootstock, then why should I have to prune it at all? Well, trees are pruned primarily to increase light on the leaves and airflow through the branches. Pruning removes dead and diseased wood, increasing tree health. Pruning can maximize fruit production and quality. Pruning can make a tree more aesthetically pleasing. Open center and central leader pruning both attempt to optimize fruit harvest, light penetration, and airflow.

A reason to prune, anthracnose cankers: Bacterial diseases like this one on apple need to be cleanly pruned out in dry weather, with sterilizing isopropyl alcohol sprayed on the pruners afterwards and the diseased material burned or sent to the landfill.

Open center, also called vase pruning, involves not allowing a tree to have leaders. Instead, main branches at roughly the same height (which can vary) spread out at low upward angles, horizontally, or even downward. Harvesting fruit from a tree trained this way is easy.

An apple tree with showing established open center form, though it should be noted that the lower branches on the left was headed off rather excessively.

Central leader pruning involves letting a tree have one leader while still having strong and well-balanced lateral branches. The shape becomes pyramidal or like that of a Christmas tree. Trees can also be pruned to have a modified central leader, where the leader is tied down or pruned in such a way as to reduce its dominance. In a modified central leader, the central leader does not grow vertically, allowing other subdominant leaders and a more rounded crown.

Central leader form

Central leader pruning can result in the tallest tree for its rootstock that  produces the most fruit possible. Modified central leader prunings can make for a shorter tree that still produces a lot of fruit. Open center pruning might result in less fruit over the lifetime of the tree, but that fruit will be easier to pick.

It might seem preferable to have less fruit and stand a chance of picking it all! A large pear or apple tree with a central leader can produce more fruit than you or the skunks and raccoons no what do with, as I can attest to being  the case with a large Shay apple tree at Raintree. That tree is overgrown (getting around to pruning it!) and on standard, full-sized rootstock. It has a strong central leader form. Another perspectives is that allowing trees to be trees and grow tall can arguably yield the most vigorous and healthiest tree. That Shay at Raintree is semi-formal and receives no supplemental water in the summertime, yet continues to produce huge crops.

The overgrown Shay apple at Raintree

A downside of open center style pruning is the main branches will be less strong because annual growth rings will be missing from a cut leader. By design the tree doesn't have a top, so the branches will only be supported by their own growth rings. Instead, where the branch leaves the trunk will develop a knuckle from repeated pruning off of water sprouts. Of course, open center can be modified in various ways as well. Pruning is art as well as science and open to interpretation! A tree can have a fairly open center while still having one dominant leader. At Raintree, the decision was made in the past to let some open center trees develop leaders for scion wood production.

On the left, the top scaffold (main lateral branch) in an open center crabapple has started tearing away. Lack of pruning probably led the branch to get too heavy and it was not strengthened by a leader putting down wood from above because the leader is cut out in open center. On the right, I have cleanly cut back part of the branch as part of gradually restoring the tree's form.

Here an open center apple at Raintree was alloed to develop a leader, strengthening the tree and increasing scion wood production potential.

Lastly, I'll discuss some of what I fathom in regards to establishing a tree as an open center or central leader. I'm still learning though, so read on elsewhere and make your own observations! Open center is recommended over central leader pruning for stone fruit ( Prunus species) like almond, apricot, peach, and plum. Either style can be applied to figs. European and Asian pears ( Pyrus species), and apples ( Malus domesticus ) can be pruned in either style, though European pears will be easier to keep in a central leader form. Quince adapt well to open center as well. Persimmons (Diospyros species) like modified central leader and so do walnuts (Juglansspecies).For open center, a whip (a young tree without much form) is topped in the first year. Then the resulting branches are tipped in the second year. This stimulates further branching in the third year and those branches can be selectively pruned to emphasize the vase-like sharp that's developing. The original branches from the second year become the scaffolds that form the vase-like shape. A central leader form is easier to develop and involves selecting a leader. If a weaker leader is selected and stronger ones pruned off, this will help control the tree's height. Heading back the leader and then training an upward sprout following that cut as the leader's replacement can start the process of forming a modified central leader. In general, in the first few years of pruning the central leader laterals should be pruned out to keep good spacing. Branches can be spread with spacing bars or staking to make 45 degree angles. In a young central leader there should be three or four  tiers of lateral branches with about four branches per lateral. The laterals should start two or three feet up the trunk and get progressively shorter going up to the leader.

This blog post could just be the start of an exploration of open center versus central leader. I know I will continue to learn about and practice these styles.

Happy growing! Because, after all, change is the only constant. -Xander Rose

References:

Hotal, T. D. "Central Leader and Modified Central Leader Pruning on Pome Fruit and Deciduous Fruit Trees not in the genus Prunus." <https://crfg.org/wp-content/uploads/Central-Leader-Modified-Central-Leader-Pruning-Presentation.pdf>. Accessed Jan 17 2021.

Ingels, C., Geisel, P. M. and C. L. Unruh. 2002. Fruit Trees: Training and Pruning Deciduous Trees. University of California, Division of Agriculture and Natural Resources, Publication 8057:  <http://homeorchard.ucdavis.edu/8057.pdf> Accessed Jan 18 2021.

Nistico, M. 2013. "Pruning dwarfing fruit trees: central leader vs open center" On Permies.com: <https://permies.com/t/13530/Pruning-dwarfing-fruit-trees-central>. Accessed Jan 18 2021.

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Source: https://raintreenursery.com/blogs/pnw-edible-plant-blog/two-tried-and-true-pruning-strategies-for-fruit-trees

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