Sunday, 12 February 2012

How to Prune

With the spring season in mind, Sue and I thought that pruning would be an appropriate topic for this months' Garden Group Meeting.

This winter with the amount of snow that has fallen, many of our trees and shrubs have been damaged and need to have their dead, diseased or damaged tissue removed. So why do we prune, what is the correct way to prune, and at what time of the year do we prune?

Why do we prune:
1. To maintain or reduce plant size.
2. Removal of undesirable growth.
3. Remove dead, diseased or broken branches.
4. To stimulate flowering and fruiting.
5. To rejuvenate and restore old plants to vigorous growth.
6. To prevent damage to life or property.
7. To shape plants into an artificial form.

What is the correct way to prune:
Trees have their own way of dealing with injuries to their branches, they are able to limit the spread of disease by transporting protective chemicals to the site of the wound, they form a barrier across the stem, isolating the diseased part from the main body of the plant.
If a plant has already formed a natural protective barrier between live and dead wood, never cut below it, or the plant will have to form another barrier (scar tissue). It is however preferable to remove dead wood as it may harbor organisms that could become a source of infection. When a plant is damaged, a clean cut beyond the damage, will heal more quickly than leaving the wound to heal by itself.
Do not use wound paints. They do not assist the healing process, they may even hinder it.

Coral spot spreads quickly and needs to be cut well back to where the surface and interior of the branch are completely healthy and clean.
If a plant has several branches, the damaged stem can be cut out at the bottom.
If your plants have frost damage - prune back to a clean bud after the likelyhood of frost has passed.
When pruning the cut should be 5mm or 1/2 inch above the bud:

When is it the right time to prune a tree or a shrub? There are a few guidelines:
Trees and shrubs that flower before the end of June should be pruned immediately after floweringowering.
Trees and shrubs which flower after the end of June should be pruned in winter or early spring before new growth begins.
Evergreen shrubs are best pruned between mid to late spring.
Prune stone fruit in the summer, winter is dangerous because silver leaf and cankers may gain entry through the wounds.
Most trees and other fruit trees are pruned in winter when the tree is dormant.

Each of our members will receive an email with as an attachment a guide with detailed pruning instructions in alphabetical order, season by season.

There are different ways of how to prune shrubs. Some shrubs are pruned each year back to a framework, this include Buddleja, Caryopteris, Perovskia and many others. In our guide it is mentioned when a shrub is pruned back to a framework.

Or like Forsythia, Philadelphus, Weigela and many other shrubs where each year a few of the oldest branches are removed and the other branches are cut back to give an overall pleasing effect.

How to prune a rose is very much dependent on what type of rose it is. Below is how you prune a Modern Bush Rose (Hybrid Tees, Floribundas, Patio, Polyanthus and Miniature Roses belong to this group).

How to prune a Modern Shrub Rose:

How to prune a Once Flowering Shrub Rose:
When pruning a Climbing Rose, only the laterals are pruned and if necessary an old can from the bottom is cut out:

With evergreen shrubs, it does not look very nice when you can see where the shrub has been pruned, take the cut just inside the shrub to hide it.

What happens to a shrub when we prune:
Most of the cellular activity of the plant is at the soft green shoot tips, just below the top most bud (the apical bud), this is the growing point or leader. It is the apical bud that imposes on the plant what is called "apical dominance". This means that only when the tip of the plant has grown away strongly, will hormones move down the stem to allow growth of the side buds (lateral buds).
This explains that when we remove the apical bud (when we prune the branches), we take away the apical dominance of the plant, which stimulates the lateral buds to start growing.

Bibliography: RHS - Pruning and Training; Wikipedia

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