At a recent pruning workshop for volunteers, Ian stressed that we should “prune weak branches strongly and strong branches weakly”. It’s a good maxim when it comes to deciding what to cut, when to cut, where to cut. He also said that apprentice gardeners were told they should be able to throw their hat through the tree, as a sign that the branches were not too crowded. But he began by looking at why to prune.
Three good reason to prune – for shape, for fruit and for health. When it comes to shape, an open canopy harvests sunlight efficiently, improves air circulation and gives your tree/shrub well-distributed scaffold branches. And give your branch a good crotch! Wide branch angles are stronger whereas narrow angles increase shading which leads to poor fruit colour, size, distribution, flavour and weaker bud development.
A gardener tries to find a balance between vegetative growth and fruit production by removing unproductive wood. This includes: fruiting wood which hangs down or is shaded, water sprouts or root suckers and weak, thin wood.
Pruning disrupts the natural process of apical dominance (the control exerted by the terminal bud (and shoot apex) over the outgrowth of lateral buds). This stimulates the growth of axillary buds. A hormone called auxin is produced in the main (apical) shoot and the removal of this promotes lateral growth and the growth of new shoots. How the tree responds to pruning depends on the variety. Different varieties and crops grow differently. The average growth rate of a tree is 15 to 18″ per year. The size and age of the tree and its rootstock should also be taken into account. Soil conditions/constraints and the level of irrigation are further considerations. Overall, the fewer cuts the better, as cutting opens the tree to potential disease.
When to prune? Most pruning takes place during the dormant season, between late winter and early spring. This encourages leaf and branch growth. For plums, cherries, trained apples and pears, summer pruning will promote fruit buds and reduce other vigorous growth.
How to prune? Pruning techniques include Heading and Thinning cuts.
The heading cut removes part of the branch, which stimulates the bud break near the cut and encourages localised branching.
Thinning cuts remove the branch at the point of origin and promote light penetration in to the canopy. This is the least invigorating cut.
Formative pruning is done on young trees around a year old and is done for 3 or 4 years.
One year old trees are called maidens and are either feathered or un-feathered. Feathered trees are sold with their side shoots attached.
Maintenance pruning concentrates on cutting out all dead, diseased and larger crossing branches.
Regenerative pruning is taking place in the Fota Orchard now where most of the trees are over 100 years old. The aim is to remove no more than 25 percent of the canopy in any one year, as this can lead to undesirable re-growth of over-vigorous watershoots. Excessive pruning stresses the trees. The following Spring, these trees should be mulched and fed with a general fertiliser to encourage good re-growth. If more than 25 percent of the tree needs to be pruned, this will be spread out over two to three years.
The Practise – Hands on in the Orchard
At our workshop, we moved from the theory session in the glasshouse to the orchard itself. The “hands-on” session began with the young trees, planted last year. The main purpose of this is to shape the tree and promote future productivity.
Firstly, look hard at the tree and plan the shaping and cutting. It’s important to try to imagine what the tree will look like when matured. This is formative pruning to establish balance and good structure.We began on our feathered maiden trees, cutting the main stem back to around 80cm from the ground and pruning the side shoots by two-thirds, to an upward facing bud. Lower shoots can be removed altogether.
Before and after pruning the young apple trees
The cut to the main stem should be made at an angle to allow rain to run off. Side shoots should be cut back almost entirely to the central stem. Overall, you’re hoping to create a future goblet shaped tree, where light and air get in.
Pruning the young trees and Ian showing how these branches can be shaped by using weights.
Next we moved on to the mature trees, mostly over 100 years old. Many of these apple trees are dense, with branches tangled through the centre. They produce fruit but much of this fruit is small and bitter. Pruning them now will help to allow air and light get through the centre of the tree (or your hat!) and encourage a better quality of apple.
This time, standing back and looking at the shape of the tree, it seems more difficult to select which branches should be removed. Sometimes it’s obvious, if the wood is dead or where the branches are growing back in towards the tree’s centre.
We began by removing dead branches. Any root-stock growing from the base can be cut off also. Many had broken off naturally, leaving stumps. After this, smaller branches were removed, including ones growing inward and immediately it opened up the inside of the tree.
Dead wood to be removed and pruning the centre of the tree
Before and after pictures of pruning of centre of tree
The volunteers really enjoyed the Pruning Workshop with Ian, we learned so much and we look forward to bigger and better fruit from the orchard next year.
In a place like Fota Orchard, it’s not just practical considerations that need to be addressed when pruning the trees or renovating the orchard but aesthetic ones also. We want the trees to be healthy and functioning but also pleasing to look at and we want to preserve their heritage as living witnesses of the passing of time.
See earlier blog – Local (Gardening) Heroes – Sally’s choice – Ard Cairn Apples
Further reading on pruning young and mature fruit trees:
(How to train branches using weights or pegs): https://garden.org/learn/articles/view/26/