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Welcome to The Green Man Arboricultural Consultancy

This website supports the consultancy business based in North Wales and which operates throughout the United Kingdom providing a wide range of arboricultural services including: home buyers tree reports, tree condition reports, development site surveys and reports, woodland assessment and management plans and general advice relating to trees.

For further information or to discuss your requirements please contact us on: 01978 821 851/ 07981 912 162 or via green.woman@hotmail.co.uk

Sunday, 20 January 2008

When Should I Prune My Trees?

There are several answers to this question, I am going to briefly discuss them all however, there is one answer I particularly want to discuss and that is 'never'.

Trees are managed for a variety of purposes including: timber production, fruit production, nursery stock, amenity, ecology, heritage, and each aspect of tree management is it's own individual industry.

Trees grown for timber production, forestry, or silviculture, are generally planted in tight grown groups at regular spacings. This introduces an early competition for light between the trees and therefore generates a crop that is straight and tall, perfect for harvesting in order to make the most of the product. Trees are generally harvested in groups. Pruning is not generally undertaken and weaker specimens or trees of poor form are naturally suppressed.

Trees grown for fruit production in orchards are similarly planted in uniform rows, at a greater spacing than for forestry, and are pruned regularly in order to promote flower and therefore fruit production. Pruning of a lead or apical shoot stimulates multiple side or lateral shoots to develop. Pruning also permits easy harvest of the fruit by keeping it within reach of the pickers.

You may even have heard of people beating trees. This again is a practice associated with fruit production; trees under stress anticipating decline or death will utilise all of their available energy to reproduce. Beating a tree therefore causing wounding may induce this state and therefore increase crop yield. (This method is not promoted.)

Nursery stock involves the cultivation of trees for sale onto all other tree related industries, and the general public, and incorporates the most important aspect of tree pruning, formative pruning. Trees develop new growth at their tips therefore the form of a young tree is same as that of the tree in maturity.

Early identification of structural defects, for example poor branch unions where the lead branch and a side branch are very close together at their point of origin, allows for formative pruning to be undertaken at a time where removal of a branch will result in a small wound easily sealed over or occluded by the tree. If the branch were to be left it would thicken along with the rest of the tree.

As the tree matures and the branch gains weight and size it may be susceptible to failure. If the branch does not fail naturally and is identified as a defect in maturity removal will result in a large wound which takes more time and energy for the tree to occlude and increases the chance of infection by providing a large area of exposed wood for pests and diseases to enter.

Formative pruning could conceivably save thousands of pounds of tree work required for trees permitted to mature with structural defects. It could also prevent the failure of thousands of trees for the same reasons. When purchasing nursery trees their form should be considered carefully and the tree, as it is, envisaged in maturity.

Trees managed for amenity covers much of our municipal tree stock including roadside trees and public park trees. Trees grown within urban settings are often subject to pruning regimes undertaken to permit traffic and pedestrians to pass unimpeded under mature canopies. Trees are also commonly pruned to permit site lines for security purposes whether this be CCTV cameras of patrolling police or security. Utility companies also regularly undertake pruning of trees to provide adequate clearance of cables, railway lines and waterways.

Trees managed for ecology and heritage are generally under a scheme of non interference save where over maturity or damage by storm render them in need of remedial works. There are also pruning techniques which encourage ecology that can be employed when remedial works are necessary in an attempt to mitigate the loss of part or all of a tree, or group of trees, which may provide valuable habitat.

The bottom line though is trees are self optimising structures designed to disperse forces evenly over their entire shape. They do this in order to effectively withstand wind, loading by means of fruit, leaves, and snow, and to successfully maintain their often enormous size in maturity. Pruning interferes with and influences that self optimised shape and can lead to and promote branch or tree failure.

Trees bending in the wind on a stormy day are dispersing forces through a graduation of branch size from the main stem and branches down to their shoot tips.

So, if you are privileged enough to have trees within your management whether they be at a place of work or within your own garden, remember to consider the full consequences of your actions. Always try and start from the viewpoint that you would rather not prune the tree at all and take it from there.

If pruning is necessary try and avoid wounding any trees during spring and autumn, when the tree is using much of its finite energy resources to either produce leaves or drop leaves.

Finally trees do develop deadwood. Stormy days, stress, disease, and many other factors, may result in the development of deadwood of varying sizes. Unless the deadwood is of a large size located over an area of high public usage it should be retained. The tree may still be utilising energy stored within the deadwood, and as development of deadwood can often indicate a state of stress further wounding may compound the issue. Deadwood also provides a valuable habitat for a multitude of insects, plants and mammals.

If you do think your trees need pruning always seek the advice of a professional arboricultural consultant. They usually offer advice for free and will be able to advise you whether further investigation is required and what if any remedial actions you should or can undertake in order to address your concerns. They will also be able to recommend a good arboricultural contractor to undertake any proposed tree works. Contractors are not all consultants and tree works and tree consultancy should be treated as separate areas of expertise.

N.B. Many arboricultural contractors have a good consultancy knowledge however this should not be assumed.

Trees should be inspected regularly by a qualified arboricultural consultant, particularly large, mature trees. It is recommended that trees are inspected every 3-5 years however, a consultant will be able to give advice on inspection frequency appropriate to your specific circumstances.

18 comments:

  1. Nice non-answer

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  2. Hello Anonymous. I am not sure how to take that...perhaps you would like to expand?

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  3. So I'm thinking mid summer is a good time to prune.....correct??

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  4. Hello! Yes mid summer is a good time to prune, alternatively late winter but if you let me know what trees you are pruning I can be more helpful as there are better times out of these options for different species.

    I am getting the feeling from your comment and the last one someone left me that this post is a little confusing or vague. If you at all felt that please let me know as I do hope to be helpful and informative but I am aware I come down strongly on the side of trees in most cases and am a little biased!

    Thanks for your visit.

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  5. While I do not wish to prune my tree (or any of my trees), I do have one tree that has grown where some branches extended across my neighbor's fence line. He has stated that if I don't prune he will. It is a chokecherry red (makes lovely berries that I use to make one of the best delicacies, chokecherry syrup). I'm getting the feeling from this post that my options are mid summer or late winter. How does one go about finding a good, licensed arborist. I'd like to find someone good, rather than letting my neighbor hurt this beatiful tree.

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  6. Hi Hana. Right, cherries, one of the exceptions! Basically prune it now or as soon as you can. Hopefully the work will not involve the removal of large diameter branches and be more tip pruning?

    Cherries are suscpetable to silver leaf, Chondrostereum purpureum, a fungal disease.

    If you prune cherries in the winter (dormant season) you leave a wound exposed for a greater period of time increasing the chance of infection.

    If you prune in the summer the tree is active and its defenses will respond quicker sealing off the wound before infection gets in. Early summer is best but if you can act quickly that should be ok.

    As for recommending a contractor try here:

    http://www.isaontario.com/pages/find_arb.php

    Its the find an arborist page on the International Society of Arborists Canada website. There are some consultants there but contractors too.

    Good luck and sorry your neighbour is unagreeable. Don't give him any syrup!

    Good luck and let me know how you get on.

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  7. Hi again Hana! Scrap that last bit. (I have Canada on the brain at the minute but that's another story!) You are in Colerado! Here is the website for the ISA covering Colerado, they do not have a find an arborist link but if you contact them they should be able to recommend someone.

    http://www.isarmc.org/pro/index.htm

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  8. Hi there

    I live on Vancouver Island in BC Canada. We have a cherry tree in our back yard that is 100+ years. We recently took over the property and needed to let everything grow and flower in order to see what needed help. The Cherry tree has some trouble spots. It has about a 4 foot tall trunk and then 2 main branches that spring from that. one of the trouble spot is a spot where a branch was cut and has over the years rotted into the trunk. If the decay continues the trunk is going to split. There are also some other larger branches that have died and need to be removed. And of course some that need to be trimmed due to property lines. So is there anything we could do for the rot problem. Secondly can I cut off the dead branches at any time? And third do I still have enough time to safely trim the live branches?

    Thanks Connor

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  9. Hi Connor. There is nothing you can do that will remedy the rot but it sounds like you are on the right track, doing nothing could cause the stem to split however I am loathed to make recommendations without seeing the tree. Would it be possible for you to email me a picture of it?

    With regard to pruning live branches as long as they are small and therefore leave small wounds I would say go ahead however again it would be useful to see the tree before anything is done.

    Trees have finite energy levels and pruning stumulates their defense using energy. I expect your tree is getting ready to drop its leaves, if it has not already started, and that also is a very energy demanding time of year.

    By assessing the tree it will be easier to say whether you should prune because it will prevent stem failure, or leave the tree until next summer when it can better cope with the wounding. You may even have to phase the pruning to allow the tree to adjust and maintain energy levels.

    My email is natalie.s@virgin.net if you want to send me a photo. Alternatively ask a local consultant to have a look.

    I hope that helps and please feel free to send me a photo, I am happy to look. Images showing the overall tree, dead branches and area of decay would be useful. (I have to warn you though I am off on holiday for two weeks this weekend and will not have access to my PC.)

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  10. Re pruning a mature tree: is excessive pruning (loss of foliage) possibly harmful to root health by depriving roots of photo-synthesized nutrients, leading perhaps to root atrophy making the tree more susceptible to uprooting in a wind storm?
    David

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  11. Re excessive pruning of mature tree; is it possible that loss of foliage might damage roots by the loss of nutrients to roots, leading to root atrophy and possible uprooting during wind storm?

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  12. Hi David,

    Thanks for your question, I have been mulling it over as I think it is a bit more complicated that that, as it always is!

    Tree roots take up nutrients and water from the soil, photosynthesis in leaves produces sugars called photosynthates which are stored by the tree throughout its woody tissue and root system for future biological processes such as growth and defence.

    Excessive pruning of a mature tree in leaf will be detrimental in several ways; the loss of foliage as you have mentioned reduces the trees photosynthetic rate for that growing season thus reducing the level of photosynthates it can generate but also removes stored photosynthates if there is significant loss of branches.

    Severe pruning will also stimulate the trees defence as it seals off the wounds caused by the pruning which will use stored energy, and may render the tree more susceptible to forces such as strong winds due to the loss of branches which enable the tree to disperse wind forces and the change in the mechanical loading of the tree by severe pruning altering the weight loading the tree has naturally developed.

    Also extensive wounding leaves the tree open to infection from pests and diseases which could weaken strength of the woody tissue.

    To conclude the loss of available energy reserves for the trees biological processes could have an impact on root growth and defence, and the change in the form of the tree could predispose it to wind throw given strong enough winds.

    There is a relationship between the root system and the extents of the tree however I would not say that severe pruning will definitely result in root atrophy but it will impact on the trees ability to maintain itself.

    I hope that helps but please feel free to come back and discuss this further.

    Thanks for your visit.

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  13. I have two beautiful weeping ash trees. They are about 120 years old. The weeping branches sweep my lawn and it has become difficult to cut the grass. Can I prune the ends back without damage to the tree and when would be the best time to do it.

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  14. Depends on how much you want to take off. I'd say play it safe, prune in mid to late winter.

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  15. Hi Angela, thanks for your comment and sorry for my delay in replying, I am afraid I missed your comment coming in.

    Thanks to Squirl also for replying and I agree.

    You should be able to prune small, twig sized growth, to achieve the clearance you require for maintaining the lawn. The important thing is to prune back to growth points and keep the branches pruned as small as possible.

    Also, pruning should be done during winter or summer, avoid autumn and spring which are energy demanding times for trees. Pruning stumulates their defence system and therefore diverts energy away from their natural processes such as bud burst and leaf drop (abscission).

    If you are in any doubt I would always recommend you consult with a professional but I think this sounds like something you will be able to do yourself.

    I hope that is helpful and please feel free to come back to me if you need any further information. My email is available on my profile page if you would prefer.

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  16. Hello, this is perhaps an old post but we have a large weeping ash in the house we moved to in Canberra Australia. I'd like to trim some medium branches but understand too much too soon could be a bad thing. Could I trim 1 every 2 weeks or so to enable the tree to cope. Fyi, we in the midst of summer right now. Thanks,

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    1. Hello, thanks for your comment. My advice would be to retain all medium and large branches where you can, over pruning is an issue for trees for many reasons, chiefly: loss of stored energy, altering its loading and causing wounding which renders it susceptible to infection however if you really have to take larger branches off then phasing tree works is usually done over a number of years not weeks to allow the tree to adapt. Is there a good tree surgeon locally you can get round to discuss this with? If you point out what you want to do they should be able to advise the best course of action and make alternative suggestions. If you wanted to you could email me some photos of the tree and I would be happy to advise further. Email is green.woman@hotmail.co.uk Thanks for your visit and comment.

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