Pruning Fruit Trees

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In February 2013 we acquired plot 4 at Choice Allotments, St Leonards, Sussex. We were overly excited as it came with FIVE established fruit trees: Two pear trees, two cherry trees and a plum tree.

I was thinking about all the preserves, chutneys and jams we were going to make, not to mention the pies and crumbles… of joy of joys, since a child I’ve always wanted fruit trees. Growing up in the leafy county of Surrey both my neighbour’s had fruit trees, cherries, plums, pears, peaches, greengage and apples. My parents weren’t into growing fruit or vegetables; they had shrubs and conifers!

The season got off to a great start. Lots of blossom and fruit buds. Those fruit buds produced so many baby fruits… I was thrilled… I buy kilners jars, loads of them…..then it all went horribly wrong. JUNE DROP!!!

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June drop is nature’s way of discarding any damaged or diseased fruit, they literally just drop from the tree. We were left with five pears and one plum. AND the birds ate our entire cherry crop because I failed to cover the trees! It wasn’t a good year and the excitement soon turned to intrigue. Why did nearly every fruit fall from the tree? How sick is this tree? So I researched it.

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Pear trees naturally grow laterally, however, the problem with this is the branches get crowded as they fight for light. Also, as the branches get crowded, it’s difficult for air to circulate making the tree more susceptible to disease.

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Ideally you want branches to create a scaffold frame like this. (See below)

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Branches coming from a central leader, or main trunk, at a 45 to 60 degree angle are best. Pear tree branches don’t naturally grow outwards/sideways, by forcing them to do so it slows up the rate of tree growth but it helps promote fruit production.

So that was it, we needed to prune our trees to bring them back to health. I’ve not pruned before so more research was required.

Pruning notes:

It’s suggested that pruning an old neglected deciduous (latin for falling off or shedding) tree should be done in stages over a number of years. Maybe set a three year plan….. patience is required….. oh dear!

The reason for this:

Hard pruning in the winter will encourage the tree to grow excessively and vigorously in the spring and it won’t promote fruitful growth.

Whilst hard pruning in the summer may stunt the trees ability to grow.

Over pruning can also lead to the production of water shoots/suckers. These suckers typically form at the base of grafted trees.  Water shoots are tall upright leafy branches that don’t produce flowers or fruit. We have one of those on the little pear tree.

There are a few schools of thought for pruning neglected deciduous trees

a) Pruning neglected trees should be done in the winter or during the dormant period, as it’s easier to see the structure of the tree without its leaves.

However, this will promote woody growth, which we don’t necessarily want.

b) It is recommended that no more than a quarter of the canopy be removed in any one year as this would lead to problems associated with over-pruning.

Good point.

c) Summer pruning, this will stimulate the least amount of woody re-growth and will promote fruit growth.

This is probably the best strategy for our requirements. We certainly need help with the promotion of fruit growth and we definitely don’t need the tree to grow an bigger. 

 

Understanding summer pruning v’s winter pruning – Deciduous Trees

To understand this we need to understand the yearly cycle of the deciduous tree.

Let’s start in the spring. Deciduous trees ‘wake up’ from a period of winter dormancy, similar to animals hibernating. During the winter, the metabolism of deciduous trees slows right down, and with no foliage or growth to support, the tree requires very little food to survive and any surplus food supplies are stored in the trees root system.

Focusing back on spring…..during spring ,deciduous trees start to form leaves which will provide the tree with a mechanism to produce a food/fuel supply throughout the season via a process called photosynthesis. Briefly, just to recap from those biology lessons all those years ago ….. photosynthesis is the process where trees/plants converts the sun’s energy into chemical energy, sugars. These sugars provide the plants/trees with fuel. Plants require a combination of carbon dioxide, water and light energy (the sun) to produce sugars. Sunlight is absorbed by chlorophyll, a green pigment located in the plants cell structures called Chloroplasts. It’s within this cell structure that photosynthesis takes place. The leaf absorbs carbon dioxide through tiny pores in the plants/trees leaves called stomata. Oxygen (the bi-product of the plant using the sugars as fuel) is also released through the stomata. Water is obviously obtained via the root system.

Okay, now think back to last year when the tree had leaves.

In theory, the more leaves the tree has the more fuel can be produced by the tree and will therefore more fuel will be available to be stored in the trees root system during the dormancy period.

On the flip side, it must therefore be true that deciduous trees with less foliage will produce less fuel, which obviously means there will be less fuel available to store in the root system during the winter/dormancy period.

So now fast forward to spring. The tree is using stored fuel to promote spring growth.  In it’s simplest form, the less fuel the tree has stored in its root system the slower the rate of growth. Conversely, trees with greater quantities of stored food will show more vigorous growth rates.

So understanding this basic principle, what impact does summer pruning have on deciduous trees?

Deciduous trees are in full leaf during the summer. By reducing this foliage it will in turn reduce the trees ability to produce fuel/food. Thus, reducing the quantity of fuel that can be stored in the trees root system during the dormant period. Therefore, during the following spring you would expect growth rates to be slowed.

Winter pruning is different. In the autumn light levels decline and leaves fall from the tree. The quantity of food stored in the tree is based on the quantity of foliage the tree had during the summer. This fuel/food is stored in the root system during the dormancy period. So what happens when the tree is pruned during the winter? The amount of fuel/food stored in the root system remains unchanged, enough to fuel a much larger tree. By winter pruning back the tree has less structure for the tree to fuel. This simply leads to increased vigorous levels of growth, as there is more food than the tree ordinarily requires.

So what did we do to our poorly fruit trees?

We did some summer pruning, to reduce the lateral growth and open up the tree to improve air circulation, ensuring we didn’t remove more than 25% of the canopy. We removed the low, dead, diseased and broken branches, and some branches that were crossing over. We did our best to create a scaffold frame structure, retaining branches that are 45 to 60 degree angles to the central leader or the trees main trunk.

We also shortened all the branches, cutting back this year’s growth to about one inch. We cut the branch to an outward facing bud, a little protruding knobby thing you find on the branches….. This is to help promote fruit bud development next year rather than wood growth. The advantage of summer pruning, it opens up the tree enabling more sun to get to the fruit buds improving the growth and flavour of fruits.

We didn’t do any winter pruning.

We are now waiting to see what happens. Fingers crossed, and legs, and toes and eyes…. Actually anything that can be crossed!

 

Posted in Pruning

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