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By November 12, 2015 0 Comments Read More →

A Guide to Pruning

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Buddleia can, and should, be pruned hard every autumn.

 

Many people are afraid to prune, as they think they might damage the tree or shrub, but damage is often done by failing to prune. Mike Clark offers a guide to pruning.

See also:

How to Prune Soft Fruits
How to Propagate Soft Wood Cuttings

 

Pruning is scary. At least that seems to be the view of many people, judging by the questions I am frequently asked. I do understand folks’ apprehensions. Pruning is an act of surgery, and surgery is rarely something we practise at home. I don’t know anyone who has taken their own appendix out, nor that of a family member. Generally, we leave appendectomies to the experts. So maybe it’s the idea of performing surgery on a shrub which causes such trepidation?

It is my task this month to demonstrate that pruning is actually not at all scary, and for the majority of shrubs, one size really does fit all. One basic approach will work for eighty per cent of all garden shrubs, and I’ll deal with the other twenty per cent in a future article.

I hate big glossy books on pruning. I have a pet – and probably very cynical – theory that on the basis that big books sell for more money than little books, publishers conspire to perpetuate the myth that pruning is complicated and therefore produce big and expensive books on the subject. I have one soft-covered pruning book, which is very good. It is also very tatty now, as a result of frequent reference – always the sign of a good book – because I cannot retain everything in my head.

Twenty per cent of garden shrubs and trees do have specific pruning requirements – clematis and apple trees, for example – and most pruning books make a real meal of this, but more or less ignore the fact that the vast majority of garden shrubs can be pruned without damage by following a simple and very basic rule: prune it after leaf-fall, unless it flowers in late winter or spring, in which case prune it immediately after flowering is over.

That wasn’t too scary now, was it?

And if you accidentally use this rule on some poor specimen in the twenty per cent category, don’t lose too much sleep. It is highly unlikely you will do any terminal damage. You may lose flowers for a year, or perhaps a little vigour, but plants are essentially survivors and won’t die if they can help it. You can make mistakes, but your shrub will usually recover far better than you would after a home-appendectomy.

So, why do we prune? The answer is essentially because nature doesn’t. Or perhaps nature does prune. In the wild, a spindly young plant throws a shoot up to reach the light, then along comes a rabbit and nips off that shoot. What does the plant do? It throws up half a dozen more vigorous shoots from the base by way of replacement.

And that’s the first reason why we prune – to encourage thicker, denser growth; and this is particularly true of hedges. I have a pretty long fuse, but I can get stroppy to the point of abusive with people who adopt the wrong approach to growing a hedge.

Golden Elder (Sambucus nigrea Aurea) displays to the max after a hard pruning.

Golden Elder (Sambucus nigrea Aurea) displays to the max after a hard pruning.

 

Do not – repeat, do not – let a hedge grow up to the height you want it to be, and then keep taking the top off. You will sorely regret creating a hedge with a few thin stems, gaps your neighbour’s Rottweiler could get through sideways, and a fluffy top. No, harden your heart! Cut your hedge back by half in the first year, then cut it back by a third in the second year… and in the third year… and so on until, despite your savagery, it attains your desired height. Why? Because every time you cut back a leading shoot, several dormant buds will produce replacement shoots, and create the thick, impenetrable hedge you have always craved. Yes, it will take a few years longer, but you can’t hurry nature along. If you want an instant hedge, buy a fence.

But of course there are other reasons to prune. Many garden plants have been adapted from the wild to become garden ornaments. We want flowers, and you have to understand a plant’s instinct to survive – procreation is the name of the game. And a plant’s response to any sort of stress is to produce flowers, and thence fruits, and thence babies, and cutting bits off a plant puts it under threat, and its natural response is to procreate before it dies – of course, we know it’s not going to die, but this is horticultural gamesmanship. Anyway, it flowers with all the enthusiasm and energy it can muster to counter the perceived threat.

Some shrubs produce their best displays on young growth. Buddleia, for example, flowers better on the vigorous young stems produced after hard pruning. The Cornus family (dogwoods) gives us spectacularly coloured stems throughout the winter, but the most striking colour will be on one-year-old growth produced after pruning it almost to the base.

Dogwoods should be pruned back hard, because the best colour is on one-year-old stems.

Dogwoods should be pruned back hard, because the best colour is on one-year-old stems.

Early-flowering shrubs like Forsythia and Ribes (flowering currant) flower primarily on the current season’s growth, so should be pruned immediately after flowering to give the new shoots the longest possible growing season.

Remove Forsythia stems after flowering.

Remove Forsythia stems after flowering.

 

 

We also prune to maintain a plant’s health, and that is because we have interfered with nature; we have cross-bred and hybridised, forever seeking better flowers, fruit, colour and whatever, but we have usually done it all with scant regard for the plant’s natural resistance to disease. And disease, especially airborne fungal disease, thrives in enclosed or congested places. So, although we might want vigorous growth, we must also retain an open shape to a shrub to allow air circulation – hence the need to remove congested growth and keep the heart of the plant open.

 

Ground-covering cotoneaster will benefit from just a light trim.

Ground-covering cotoneaster will benefit from just a light trim.

 

A basic, eight-point pruning plan

1           Cut out all dead wood back to healthy growth.

2           Always prune to about 1cm above a bud, because new growth will come from a bud, and any stem left above will die and provide an entry point for disease.

3           Alleviate congestion in the centre of the plant by removing any shoots that cross, or rub against other shoots.

4           If pruning to restrict size, on most plants you can cut back as hard as you like, but always follow Rule 2.

5           Remember that the most vigorous new growth will come from the first bud below your cut, so where you prune can actually determine where you want the plant to grow from.

6           If your plant is congested, prune to an outward-facing bud – the new shoot will grow outwards instead of inwards.

7           The most common mistake is not pruning hard enough.

8           Never let the so-called experts frighten you!

So, please remember this – shrubs are forgiving and will almost always recover from a mistake. And above all, a home-appendectomy is extremely scary, but pruning your garden shrubs is not! Over the next couple of issues I will continue to hold your pruning hand, and hopefully help you with fruit trees, roses, clematis and all those which do require a wee bit of special treatment. But even that’s not scary either. Everyone can prune!

If you have to remove a branch that is too big for your loppers, you will need a pruning saw. And the three biggest dangers with removing any large branch are:

 

*           The weight of the branch may cause a tear on the main stem, which will provide easy access for fungal diseases.

*           Branches are always heavier than they look and might fall on the family dog or a wayward child.

*           If you are in the wrong position a part-cut branch may swing down on you, with consequences for your unguarded parts.

To avoid damage to the tree, yourself, pets and children, you must use an undercutting technique.

UNDERCUTTING

1           Make your first cut at least 30cm from the main stem, and make this cut upwards from the underside. But don’t go more than a third of the way through, or the branch will trap your saw.

1 Make your first cut at least 30cm from the main stem, and make this cut upwards from the underside. But don’t go more than a third of the way through, or the branch will trap your saw.

2           Make a second cut from the top, about 2.5cm further away from the main stem.

2 Make a second cut from the top, about 2.5cm further away from the main stem.

3           Keep cutting – the weight of the branch will complete the cut, and the undercut will prevent any tearing. But beware – it will drop suddenly.

3 Keep cutting – the weight of the branch will complete the cut, and the undercut will prevent any tearing. But beware – it will drop suddenly.

4           Cut the stub as close as possible to the main stem from the top. There is no weight now to cause a tear, and your last cut will be clean. If necessary, tidy up any rough edges with a sharp knife to reduce the risk of fungal infections, but don’t bother with healing paint products – the tree or shrub is perfectly capable of healing itself.

4 Cut the stub as close as possible to the main stem from the top. There is no weight now to cause a tear, and your last cut will be clean. If necessary, tidy up any rough edges with a sharp knife to reduce the risk of fungal infections, but don’t bother with healing paint products – the tree or shrub is perfectly capable of healing itself.

 

 

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