Terry O’Regan continues his feature series on issues relating to landscape design with trees
| On a family holiday in the Algarve, Portugal in the early 1990s we took a ‘safari’ trip up into the wooded hills. I was struck by the contrast between the birdlife evident in the native oak groves as against the lack of birds in the new alien eucalyptus forests. However, I cannot remember if flies were also missing, but I do remember the unsettling discordant noise of the eucalyptus leaves moving against each other in the warm breeze.
In recent days I specified some tree planting for a new project in compliance with a planning condition. Nothing too fancy – lime, hornbeam, oak, mountain ash, birch, etc. I spaced the trees reasonably well apart and well out from walls, kerbs and buildings. It was an almost unconscious exercise informed by experience and observation as much as by training and study, but I was conscious that if they all grew to maturity there would be too many trees. (I always caution clients that selective thinning will be required in time.) As is so often the case, I was trying to strike the difficult balance between some immediate impact and the natural imperative of living trees to grow and more than fill their allocated space. The consulting engineer for the project did ask for assurance that the tree roots would not in time damage the service roads and kerbs. I advised him that, within reason, I had made allowance for same, but I also remarked that the increasing early “Increasing early obsolescence of buildings nowadays was such that the site would probably be recycled for a different project well before the trees reached that possible stage”obsolescence of buildings nowadays was such that the site would probably be recycled for a different project well before the trees reached that possible stage. A few weeks later I had a call from the same consultant about my landscape scheme. “The client wants to know will the trees give rise to flies on the site as they may pose a problem for the manufacturing process.” I had met this concern on previous sites, but the answer then was to exclude trees in the vicinity of air intake vents. I had not come across a general request for all trees to come without flies. The constraints involved with this project highlight the demanding assessment process involved today in landscape design with trees. On the one hand, there is the pressure from the planning process to have as many trees as possible and indeed there is a wide range of valid vital reasons to plant trees on project sites, be they manufacturing, service or residential. Then the design team minimises the areas available for planting. After that, you may have to exclude the water-loving trees like alder and willow. Factor in the growing lists of exclusions due to pests and diseases. And now do a risk assessment on which trees will fall and kill someone in 30 years’ time, which trees will trip up pedestrians, which trees will drop too many wet leaves giving rise to slips and falls, and which trees will cause structural damage to something at some future date. And what about the flies that just might close down a manufacturing plant? |
You have professional indemnity insurance, I hope. Joking aside, this is a serious matter. If there is a future problem or incident you may be involved in litigation and compensation scenarios. So in taking our decisions do we have the backup of regulatory standards and guidelines for landscape design and construction in Ireland? The simple answer would appear to be ‘no’. For example, check out the building regulations on the Department of Housing, Planning and Local Government website and you will find everything but a tree. There is a long list of technical guidance documents, but nothing on landscape design and construction. You might think there are clear consistent official guidelines out there somewhere, but I suggest that if you go looking you will end up confused, frustrated and probably angry.
Take the question of the recommended distance of new trees from buildings and structures. There would appear to be a dearth of current clear guidance in Ireland. I checked back to the excellent in its time ‘Manual of Urban Trees’ by John McCullen and Richard Webb, published by the long-defunct Foras Forbartha back in 1982. It had a comprehensive chapter on designing with trees, but it does leave the final decision on distances from building and structures up to the designer. I would have to ask if that flexibility leaves the designer far too exposed in today’s nasty litigation game of ‘find the fall guy’.
I came across a Department of Agriculture, Food & Forestry publication (S135 2008 – Minimum Specification for Screening Belts and Shelter Belts for Farmyards and Buildings) which recommends that to avoid “possible root damage to structures trees should be set about 20 metres or more from buildings, yards, concrete tanks, silos, etc”.
Then there is the more recent BS 5837:2012, which whilst not an Irish publication is the current default source and ‘tree bible’ for many. I mentioned my reservations about its guidance in my last article. There is a reasonably good section (5.6) on new planting design which provides guidance rather than prescriptive recommendations. But there is a questionable table in Annex A of the standard, setting out the minimum distance between new planting and structures to avoid direct damage from future tree growth. This table just does not make sense for me. For example, it recommends that a tree with an ultimate trunk diameter of between 300 and 600mm may be planted 0.7m from a lightly loaded structure such as a garage. I would anticipate problems there within 10 years. I am of the view that most if not all of the distances in that table are far too close.
They do make the point in the text that roots do not try to go through structures, but rather adopt a lateral approach and grow around obstacles. But that surely is too simplistic a justification for very short minimum distances. The expanding trunk diameter and root mass heave will cause problems in time, not to mention the loss of light over the dark winter months and the leaves clogging the gutters.
I even checked the RHS site for their advice on trees near buildings and again, it left me feeling distinctly uneasy. It seems to me that those of us who believe we should plant as many trees as possible are in denial about buildings and structures, and those of us who believe we should concrete over the planet are in denial about trees and the lives they lead.
The musical ‘Oklahoma’ features a lively song urging the farmers and the cowboys to be friends. Maybe we need a new version urging the builders and the gardeners to get together to produce agreed guidelines that must then morph into the long overdue regulations.
And to do so we will not need to re-invent the wooden wheel – just download from the Leeds City Council ‘Guideline Distances from Development to Trees’ from the internet and you will see what I mean. Though I have to admit that it does not tell me how to ensure that my trees come without flies. ✽
 TERRY O’REGAN, B Agr Sc Hort(Hons), FILI, MIoH, founder of Landscape Alliance Ireland, has served the landscape industry in Ireland for some 45 years and advanced the intent and aims of the European Landscape Convention for some 20 years.
He now divides his time between providing landscape consultancy services in Munster and working as a Council of Europe international landscape and heritage expert in Kosovo. He continues to promote and refine his ‘jargon-free’ landscape circle methodology and is currently leading a pilot study on its use at local and regional administrative levels in Kosovo. The LAI website will shortly be relaunched as www.lai-ireland.com. Contact Terry at terryjoregan@gmail.com or 021 487 1460. |
