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Trees in Gardens
by Rowan Adams
Why have trees in your garden?
Trees are the biggest and longest-lived creatures on Earth. They can give a garden its framework, and give more beauty for less human effort than any other plants - all they usually need back from us is some appreciation. Gardening with trees is more sustainable than having large areas of short grass and annuals.
Living with trees in your garden
Keep your eyes open! The best tools for looking after your trees are your eyes. Watch your trees and see how they change. If they begin to look unhealthy or unsound, call in professional advice.
Are trees dangerous? Nobody can guarantee that a tree is completely safe, but most trees will be sound and healthy enough most of the time. A tree may be big, or tall, or have long heavy branches, but still be safe - trees adapt by growing strong enough to take the forces on them. Many trees hollow out over time quite naturally, and may even be safer hollow than solid.
Trees absorb wind energy by swaying - if they didn’t sway they’d snap! Call in a tree consultant only if a tree moves right down to the ground, or if the ground moves. Ivy can increase the windload, but it gives shelter and food for insects and birds. Only cut it back if your garden is especially exposed or if it is growing over leaves.
Free compost! All trees drop dead leaves. Some trees naturally shed bark, and most trees will shed twigs and small branches as part of their natural pruning, when other branches shade them out. You can turn all of these into leafmould and compost. If big branches fall, there may be something wrong - get professional advice.
Tree work is not like most other gardening work, and is not for the amateur.Dangerous gardeners Ordinary gardening can damage your trees, especially the roots, through mechanical damage, compaction, or heat:
• Don’t change the ground level around trees - don’t remove or add soil below trees.
• Don’t cover the soil around roots with anything heavy which could suffocate them.
• Don’t cover the soil around roots with hard impervious surfaces which will stop air and water getting through -this includes concrete, plastic pond liners and slabs.
• Don’t mow or strim close to trees - plant ground cover and/or mulch instead.
• Don’t put your compost heap below trees - heat and compaction can kill roots.
• Don’t light bonfires under or near trees - the heat can kill roots, bark, cambium, leaves and buds.
Trees and houses If you are trying to move house, your surveyor may be concerned about trees nearby - get a report from a tree consultant.
Under control? Trees grow! A tree will regrow after it is pruned. You can keep it to a certain size only by spending money as long as it lives to have it pruned regularly. It is better to learn to live with the tree at its natural size, or to consider replacing it with a tree which will naturally grow to a smaller size.
Tree inspections Many people assume that tree branches and twigs are like hair that needs a regular trim, but leaves are more like the trees’ guts and lungs - we don’t need to have our vital organs pruned, and neither do trees! Unlike us, trees can recover from having bits cut out, but pruning does open up wounds, and these may decay.
Tree surgery is usually only needed because people are competing with each other and with the trees for space. The smaller the risk that the tree or bits from the tree could fall on somebody else, the smaller the need for tree surgery. If any of your trees overhang public land, or somebody else’s private property, you should have your trees regularly inspected by a tree consultant who has professional indemnity insurance.
Tree Surgery and Tree Contractors
Tree work should be taken seriously, for the sake of people’s safety, and for the tree’s beauty and health. Tree work is not like most other gardening work, and is not for the amateur. Don’t do any work yourself - if you can’t reach a branch from the ground, employ a professional tree surgeon.
Some common reasons for tree surgery:
• Elm tree killed by elm disease - remove as soon as possible to slow down disease spread; don’t move timber with bark attached.
• Other trees - remove whole tree or large branches over public land.
Risk of direct damage.
• Overhanging buildings: remove tree or reduce crown.
• Overhanging footways: raise crown to 8' (2.4m).
• Overhanging roads: raise crown to 13' - 18' (4 - 5.5 m).
• Walls: if closer than 2 m may need to remove tree.
• Overhead electricity lines: contact Southern Electricity.
• Overhead telephone wires: prune back to suitable growing points to give 3 m clearance.
Indirect damage (subsidence).
• Ask a tree consultant and building surveyor / structural engineer for advice.
• By wind, salt spray, disease, frost, or bad pruning; may be sensible to cut out damaged branches back to suitable growing points. Only if safe leave deadwood on the tree to provide habitat for insects and birds.
Competition between trees.
• Remove weaker trees, or sometimes can prune to keep both.
Increasing fruit production.
• This is a specialised skill - ask somebody experienced
Letting in more light, or opening up views.
• Raise, thin or reduce crowns; or remove trees and maybe replace with different species
Main types of tree surgery
Crown lifting/crown raising: the removal of the lowest branches, side branches, or parts of branches. The process is usually defined by the height of the lowest branches after surgery, for example "raise crown to 3 m above ground level". This lets more light and wind under the tree, and gives more room for people to walk underneath.
Crown thinning: the even removal throughout the crown of selected branches, side branches, or parts of branches back to growing points. It is usually defined as a fraction of the crown to be removed, for example "thin crown by up to a third". Thinning lets more light and wind through the tree.
Crown reduction: the removal of the outermost parts of branches, or side branches, back to growing points, to reduce the tree’s height and spread. Reduction is usually defined as a fraction of the crown to be removed, for example "reduce crown by up to a fifth", and/or by the maximum length of branch to be removed, and/or the size of the tree afterwards, for example "reduce crown, removing up to 4 m, to leave crown 15m high by 10 m wide". The process lets more light and wind above and around the tree.
Often a combination of crown lifting, thinning, and reduction may be used. Other work may include deadwooding, removal of dead and/or dying branches, and cleaning out (removal of broken branches, crossing branches, stubs from previous bad pruning, and climbers like honeysuckle, ivy, wild clematis).
Coppice and pollards: trees can be cut back regularly to the same points and stay healthy only if this is done from an early age by somebody with experience. Coppicing (cutting to ground level in woods) and pollarding (cutting to a 6'-15' stump in wood pasture) were traditionally used to produce poles for building and fuel. Ancient or veteran trees are often old pollards. In gardens, coppicing can be useful to stabilise steep slopes. In streets or gardens a form of pollarding can be used which leaves a framework of branches. Like pollarding, it should be started when the tree is young.
Where to cut, how much, and when: cuts should be made at a side fork to leave a flowing branch line, and at the natural division between the branch and its parent stem, just outside the branch collar and branch bark ridge. This leaves a ring of tissue which will grow as woundwood over the cut. Don’t remove more than a third of the tree’s leaf area. Don’t remove branches which are more a third of the thickness of the parent branch or trunk.
The best time is different for different species, so ask the contractor for advice. Avoid the time around budburst in spring (it is illegal to knowingly disturb a bird's nest when it is in use) and around leaf-fall in autumn.
Choosing and employing a tree contractor
See Tree Consultants and Contractors. Tell the contractor why you want tree surgery; a good contractor will advise you on the best way to get what you want. Tell them about any potential hazards you know about. Agree on how they will get access to the tree, and ask permission from your neighbours if necessary. Let the contractor organise any necessary road closure with the highway authority and the police. Decide how you want the tree or branches to be left - as timber, firewood-sized logs (use a cleanburn woodburning stove) or chips. (Avoid bonfires - they are a waste of timber, fuel, and mulch. Sparks may start fires in thatched buildings.) Leave dead wood in logpiles for wildlife. Ask for a written quotation and specification. You may want to ask two or three companies for quotations, but the cheapest may not be the best value for money.
Do you really need to work on your trees?
What not to do: topping
'Taking the top out' is not the same as pollarding. It will not stop the tree growing. If a mature tree is suddenly cut for the first time, the trunk and branches are cut off midway, rather than to a growing point. This weakens the tree, and decay will increase. The new growth appears vigorous, but it will be weakly attached to the trunk, and will be more likely to break in future, so the tree then has to be cut regularly for the rest of its life. The tree can become dangerous and unhealthy as well as ugly. If you want a tree to be made smaller, don’t get it topped - ask for a proper crown reduction with cuts made to growing points, and remember that any reduction will be temporary. Consider replacing the tree or learning to live with it as it is.
Trees can be important for wildlife, especially squirrels, birds, insects, birds, bats, and lichens. Trees give shelter and food. Ancient or veteran trees are especially important. Dead wood can be especially important for insects (and so for birds) - leave dead wood in the tree if it is not dangerous, or leave some dead wood and wood from tree surgery as habitat piles for insects and other "minibeasts".
Some species and habitats are protected by law under the Wildlife and Countryside Act, and you, and the contractor, could be prosecuted for damaging them. For example, you should not tell a contractor to remove a tree or to do tree surgery which would destroy shelter for bats, red squirrels, dormice, or nesting birds.
Woods, especially ancient woods, are important habitats. If your garden includes a wood or part of a wood, it will be better for wildlife if you manage it as a whole habitat - it is not just a collection of trees in an ordinary garden. Some woods are protected under the Wildlife and Countryside Act. Get professional advice before starting any work. Woods may also be protected by Tree Preservation Orders - obtain consent for any work.
You can also join the National Small Woodlands Association, which is an independent group run by and for small woodland owners, and they can advise you.
by Rowan Adams, former Tree and Landscape Officer, for the Isle of Wight Council. Reproduced by kind permission.