Steve's answers to Tree Wardens' questions


On horse chestnuts with leaf miner, is bleeding canker terminal and infectious?

Leaf miner can continue for many years and, on its own, is unlikely to kill the tree, however it does weaken the tree which makes it susceptible to other diseases and Canker is the most likely. Chondrostereum (Silver Leaf) is also able to attack weak trees, but I would suggest following canker infection. In terms of infection this is not conclusive, it may require wounds to infect (which may include naturally occurring lenticels, or pores, in the bark) or might exist on plant surfaces and be spread by wind-blown rain. It is much like Phytophthora, which would make any tree within the area susceptible and is terminal if infection girdles the whole tree in the lower stem. See link below to Forestry Commission where a recent page has been set up for all the main tree pests and diseases with links to detailed information. This is a great resource and should be on every Tree Wardens favourites.


Tree Preservation Orders - What new amendments have been made?

The reason for the changes was to consolidate and streamline the TPO system. The new Town and Country Planning (Tree Preservation)(England) Regulations 2012 came into force on 6th April 2012. The new regulations refer to all previous as well as future TPO's. Existing powers to make tree preservation orders when granting planning permission, or in the interests of amenity, remains unchanged. These changes do not alter the level of protection provided to trees.

Key Changes
Immediate protection - All new orders provide immediate provisional protection that lasts for six months and long-term protection once authorities confirm them after considering any objections or representations.

Informing interested parties - Local authorities will only need to send copies of the order to owners and occupiers of any adjoining land where they have a right to prune or fell the trees covered by the order. Authorities can notify others, but this is discretionary.

Exemptions - Consent is not required to carry out work to protected trees that are dead or dangerous, the new regulations omit "dying" from the exceptions. They also introduce an exemption for removing dead branches from a living tree.

Notification of intention to carry out exempted work - Tree owners have to give at least five working days written notice of proposed work on dead trees, unless there is an urgent risk to safety.

Consents - The power for local authorities to modify or revoke consent they had granted for specific work has been removed.

Default period for duration of consents - There is default period of two years for work on protected trees to be completed; however the local planning authority can vary this if appropriate.

Replacement trees - The new regulations remove the need for directions for replanting in woodland by enabling conditions to be used in all cases where replanting is required.

Compensation claims to the local planning authority for loss or damage arising from refusal of consent or conditions - The compensation framework for orders made on or after 2 August 1999 are extended to all tree preservation orders by removing the power to issue article 5 certificates. The same compensation framework therefore applies to all orders, irrespective of when they were made.


Tree Preservation Orders - Is an owner required to keep a tree, subject to a TPO, in a healthy condition? What legal and other obligations are there on the owner?

There is no requirement to maintain trees in good order if protected by a TPO or if in a Conservation area. However, carrying out actions that induce decline would be an offence under the TPO regulations. The law requires that people should take reasonable care to avoid acts or omissions which cause a reasonably foreseeable risk of injury to persons or property. The generally agreed standard to be achieved is that of a reasonable and prudent landowner. If you are aware of a defect in your tree and damage subsequently results, you may be held liable for negligence. The duty of care extends even to persons who may trespass onto your land.

What 'being aware of a defect' is not defined in law, but is considered to be what would be expected of a reasonable and prudent landowner. I suggest that a person with an interest or knowledge of trees would be expected to have a greater awareness than a complete layman. I would also suggest that if an issue is brought to the attention of an owner then it is 'reasonable and prudent' to investigate it further.

Reasonable tree management has both reactive and proactive elements. While an owner may need to react to events involving dangerous trees as they arise, it is also prudent to have forward-looking procedures to keep tree-related risks at an acceptable level. Trees are complex structures that are easily damaged by poor or ill-advised work, tree work is also a dangerous and skilled operation, I strongly advised owners to engage a professional tree surgeon or arborist to advise and to undertake any work needed, particularly when dealing with protected trees.

In terms of legal enforcement trees are the same as scheduled ancient monument and listed buildings, there is no commitment to maintain in good order but carrying out operations that have a negative effect is an offence. Do I think enforcement to maintain trees in good order is necessary? Probably not, as long as tree protection is properly applied.


Unlike commercial woodlands, most trees and shrubs in towns and villages are planted to provide beauty or shade. Whilst these are excellent benefits, what other benefits do trees provide?

There are numerous benefits that trees provide and these can be grouped into four areas - social, communal, environmental, and economic.

Social Benefits
Human response to trees goes well beyond simply observing their beauty. We feel serene, peaceful, restful, and tranquil in and around trees. We are 'at home' there. The calming effect of nearby trees and urban greening can significantly reduce workplace stress levels and fatigue, calm traffic, and even decrease the recovery time needed after surgery. It has been shown that recovery times in hospitals are faster if the patient can see trees from their window. Trees can also reduce crime. Residential buildings with larger areas of green space including trees have lower crime rates than those without trees.

The stature, strength, and endurance of trees give them a cathedral-like quality. Because of their potential for long life, trees are frequently planted as living memorials. We often become personally attached to trees that we, or those we love, have planted. The national arboretum and local planting schemes are both examples of this emotional link. The strong tie between people and trees is often evident when trees come under threat; communities speak out against the removal of trees for development or rally to save a particularly large or historic tree. Our planning system even enables protection of trees through Conservation Areas and Tree Preservation Orders.

Communal Benefits
Even when located on private land, the benefits provided by trees can reach well out into the surrounding community. Likewise, large-growing trees can come in conflict with utilities, views and structures that are beyond the bounds of the owner's property. With proper selection and maintenance, trees can enhance and function on one property without infringing on the rights and privileges of neighbours.

City and town trees often serve several architectural and engineering functions. They provide privacy, emphasise views, or screen out objectionable views. They reduce glare and reflection. They direct pedestrian traffic. Trees also provide background to and soften, complement, or enhance architecture.

Trees bring natural elements and wildlife habitats into urban surroundings, all of which increase the quality of life for residents of the community.

Environmental Benefits
Trees alter the environment in which we live by moderating climate, improving air quality, reducing storm water runoff and harbouring wildlife. Local climates are moderated from extreme sun, wind and rain. Radiant energy from the sun is absorbed or deflected by leaves on deciduous trees in the summer and is only filtered by branches of deciduous trees in winter. The larger the tree, the greater the cooling effect. By using trees in towns and cities, we can moderate the heat-island effect caused by pavements and buildings.

Wind speed and direction is affected by trees. The more compact the foliage on the tree or group of trees, the more effective the windbreak. Rainfall, sleet, and hail are absorbed or slowed by trees, providing some protection for people, animals and buildings. Trees intercept water, store some of it and reduce storm water run-off.

Air quality is improved through the use of trees and shrubs. Leaves filter the air we breathe by removing dust and other particulates. Rain then washes the pollutants to the ground. Leaves absorb the greenhouse gas carbon dioxide during photosynthesis and store carbon as growth. Leaves also absorb other air pollutants such as ozone, carbon monoxide and sulphur dioxide, and release oxygen.

By planting trees and shrubs, we return developed areas to a more natural environment that is attractive to birds and wildlife. Ecological cycles of plant growth, reproduction and decomposition are again present, both above and below ground. Natural harmony is restored to the urban environment.

Economic Benefits
Property values of landscaped homes are 5 to 20 percent higher than those of non-landscaped homes. Individual trees and shrubs have value, but the variability of species, size, condition and function makes determining their economic value difficult. Trees increase in value as they grow. Trees, as part of a well maintained landscape, can add value to your home.

The indirect economic benefits of trees within a community are even greater. If we use less energy to cool or warm our homes due to the benefits of trees, then power suppliers build fewer new facilities to meet peak demands, use reduced amounts of fossil fuel in their furnaces, and use fewer measures to control air pollution. Communities can also save money if fewer facilities must be built to control storm water in the region. To the individual, these savings may seem small, but to the community as a whole, reductions in these expenses are often substantial.

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My neighbour's tree overhangs my property. Can I prune the tree?

Yes, you are entitled in law to prune back any overhanging branches to your boundary line but not beyond it. You should not trespass onto your neighbour's property to do the works, unless you have permission. You are obliged by law to offer any parts of the tree removed back to the owner before you dispose of them.

If a tree is protected by a Tree Preservation Order, or is within a Conservation Area, then you must apply to the local planning authority for permission to prune the tree. If you are unsure whether a tree is protected or not, contact your local Arboricultural Officer.

However, I would strongly advise that you speak to the tree owner before carrying out any pruning of the tree, as they may well agree to carry out more appropriate works to the tree. Cutting back to an arbitrary line dictated by a legal boundary does not represent good tree management and for the welfare of the tree should be avoided. It is always better to talk before rather than argue afterwards, not only for you but ultimately for the tree.

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How do I prune a weeping birch tree?

Birches produce strong sap flows so you must prune them before the sap starts to flow in late winter (February) or the cuts will not heal well. Weeping Birch is a grafted tree usually at around 2m. When young, prune to one central stem with a few good side branches. Remove branches below the grafting line. Always remove the whole branch outside the branch collar. (On a birch the collar is easy to locate because there usually is a blackened line running down the trunk at the spot where the branch is joined to the trunk. This line indicates the location of the branch collar.) Otherwise cutting a branch back partway will produce a twiggy growth. Trailing branches may be trimmed to a bud or side shoot if they are in the way.

In order to encourage the growth of a main branch strong enough to support the current and future weeping branches, a bamboo cane or other stake should support young trees. You should not need to train the branches to weep if the tree has been grafted properly. The upright growth should start to weep over to the sides once it has reached the optimal height.

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Does each of the tree roots provide nutrition to the entire tree or just a section of the tree?

It is the small fibrous roots that get the nutrients and water from the soil; the larger roots are mainly for transporting the nutrients and water up to the tree. Each of the roots is responsible for a certain part of the tree. So if you were to cut off some roots, only the parts of the tree that they served would be affected.

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What are the biggest trees in the world?

Coastal redwood (also known as the giant redwood) grows in a relatively small area just off the coast of Northern California. They like the distinctive humid climate, with fog that occurs almost every day. This fog helps to provide the ideal conditions for the trees to grow so large. They can live for up to 2,000 years. They are generally regarded as the tallest trees in the world, with heights of up to 379 feet. They can be up to 22 feet in diameter at their bases, and it is estimated that they can weigh up to 1.6 million pounds.

Giant sequoias are genetically very similar to the giant redwoods, but grow in a significantly different environment. The sequoias grow in California's Sierra Nevada high mountains, at elevations up to 7,000 feet above sea level. In contrast to the growing conditions needed by the redwoods, giant sequoias require times with dry heat in order to thrive. Giant sequoias can live for well over 3,000 years. Not as tall as the giant redwoods (sequoias grow to just over 300 feet tall) but, because they are much thicker, they are considered to be the largest (in terms of total weight) trees in the world. They can weigh more than 2.5 million pounds, and have trunks measuring over 40 feet in diameter at the base.

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Why does the bark of silver birch trees seem to become fissured as it gets older and does this mean it doesn't have long to live and is it then more susceptible to disease?

Firstly I have to say that of all the elements of a tree the bark is probably the least studied, however it is an interesting and important part of the tree. It is essential to the growth of all woody plants. Bark protects the tree from disease. Bark contains phloem tissue, which brings the food produced in the leaves down to the rest of the plant.

One feature of bark is that it grows throughout the life of the tree. It has to grow, as the rest of the tree, mostly wood, is growing inside the bark. The fissures in many types of bark are because it is, as it were, stretching to accommodate this growth of the wood within. It doesn't just stretch. The oldest bark comes off, pushed by pressure from within. It can be affected by adverse weather i.e. extremes of both hot and cold and a little bit like our skin tends to become more fissured the older it becomes.

Bark is a useful identification tool as it is always present when leaves and flowers are not.

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Why do some trees like walnuts seem to shed their branches in the winter. Is this connected to global warming or lack of water?

Many species shed branches in the winter, they do this for much the same reasons as they do their leaves, as the tree closes down for winter small twigs are isolated/closed down and are shed in some cases growth up to 8 years old can be shed.

Beech trees are known for dropping branches and often loose limbs can be seen hung up in the crowns; however this is often the result of Squirrel damage ring barking branches high up in the crown. There is a suggestion that shallow rooted species are less stable in strong winds and it is better for the tree's survival to lose limbs rather than fall over. Often a branch carrying too much weight, particularly when the sap is rising will be shed. There are also incidents of limbs being lost in hot dry spells.

This would tend to indicate that trees will shed limbs in extreme circumstances to ensure their survival, there is no doubt that climate change will have an impact on trees both due to longer periods of dry hot weather and the increased number of storm events.

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