PRUNING 1 - WHY PRUNE?

Posted on 30 Jan, 2008 5 comments

Ask many gardeners why they prune their shubs (and climbers) and they will tell you it’s because they have got too big. But this is not the plant’s fault – it’s been planted in the wrong place or too close to its neighbours. The real reason is so the plant performs better. Some things don’t need pruning. For example daphne mezereum makes a round shape with well-placed growths but others, like a buddleia, become a huge mass of old and jumbled wood, flowering right at the top almost out of view. Some things respond well to being cut back – mahonias sprouting from just above a leaf joint – while others, notably most conifers but also the witch hazels, will not break from pruning cuts. Experience or a good gardening book will tell you whether to prune and what results to expect.

So what are we looking to achieve when we get out the secateurs? The first thing to look for is any dead or diseased wood; this is the first to take out. Next on my list is air flow. Stagnant air in and around a plant encourages disease; a plant with an open centre allowing good air circulation is less prone to problems. So I remove any shoots growing towards the centre of the bush or crossing branches, always pruning to a bud in the direction of the growth I want to encourage. We want to encourage flowers or fruit or maybe stem growth if the young wood has coloured bark. Removing old wood encourages the plant to ‘make good’ the ‘damage’ by making new growth which is more prodctive than old, tired branches (but in the case of fruit trees, we are trying to increase the number of fruiting spurs consistent with what the tree can carry without exhausting itself). Take your time and think about each cut – as my father once said, “There’s no such thing as a putting-on saw, only a taking-off one.” The finished result should be a well-shaped plant with an open centre. Cutting to shape or reducing the size I call “cosmetic pruning” – it has its place but don’t think of it as just a hacking-back job. Yesterday for example, I reduced the spread of the lower half of a large skimmia but left the upper half intact; now it doesn’t look to have developed middle-age spread but still has a natural-looking outline. Some shrubs, such as pyracantha, do not form a good shape and will throw branches in all directions; removing some of these completely will improve their appearance.

Wall-trained plants need slightly different attention – here the process it to retain a plant growing parallel to the wall rather than towards or too far way from it (although many shrubs, including ceanothus, will gradually increase in girth over the years and trying to limit this usually means removing the wood to carry the next crop of flowers). Topiary (and hedge-trimming) is an artificial form of pruning where the shape of the resulting plant is the raison d’etre. And finally, don’t neglect to cut out any growths on variegated plants that have reverted to green; they contain more chlorophyll than the other shoots and, if left, will take over.

Comments

Spritzhenry

When we moved here, there were quite a lot of unpruned shrubs and I didn't really know how far back to cut them, or when. Having waited a season or two to identify them, I bought a book. Then I found that books on pruning are not terribly helpful, either, as they say things like 'take one in three branches out to ground level'. I asked our lovely tree surgeon to come round and give me a pruning lesson, which he did - and gave me the confidence to do it myself.. Your advice is so clear, Andrew, I think that for anyone without a 'tutor' on hand, 'Andrew's on-line tutorial' should be of great benefit. The only bit you haven't gone into is the timing of pruning for spring flowering as against later flowering shrubs - could you do another tutorial about that, do you think? I fall down on pruning climbing roses, I don't dare to get vicious enough. (Nor can I climb up ladders! lol)

30 Jan, 2008

Andrewr

That's coming tomorrow spritz!

30 Jan, 2008

Majeekahead

thanks Andrew, really usuful advice, i have been having a careful chop of a few things recently, but not to experienced in pruning to be honest,as previous to having my lovely long garden that i have now, i only ever had postage stamp size plots, so i was limited to what i could grow in my tiny space so generally opted for small or low growing plants that don't require too much. but in my new garden i have quite a few that will need an annual hair cut. could you give me any advice on how and when to cut back a mock orange? i have one right next to the patio which has been there for years, i did try to takle it last year but i think i must have done it wrong or at the wrong time. it did'nt flower at all and the shoots that did spring up were very tall and leggy - some as tall as 20ft. so as soon as there was a bit of wind they fell over and snapped. it has loads of dead wood in the center which is difficult to get to with a saw and far too fat for secatures but i am worried that if i cut out all of the dead bits i will damage the rest of the plant would be a shame to loose it. i cut it back to about 3ft last spring, and it now just looks like long flimsy twiggs that are well over 20ft high. and it seemed to be prone to all sorts of pests, dispite lots of spraying and endless amounts of organic soil improver dug in around the base. any of your expert advice on this would be most welcome as it would be a shame to loose it, but it just looks awful the way it is. thanks

30 Jan, 2008

David

At last! A lovely guide to a scary topic - and one that did not send me to ZZZzzzzzzzzzzzzzz! You'd better check my response, written a few minutes ago, to Patrick's question, however. Many thanx!

30 Jan, 2008

Katcod

So informative! Just what I was looking for, thanks AndrewR. My other laburnum (the wayward one) has branches higgledy piggledy, criss crossing etc. Have hesitated pruning so far as I think it's supposed to be done in winter? Is that right?

25 Aug, 2008

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