Please see below for the latest technical updates of interest to Tree Wardens and Tree Warden Coordinators, clicking on the green links will take you to the relevant section.
Hedge cutting and wildlife law
Strategy tackles pest and diseases
Disease hits London planes
Adopt a tree for citizen science
Watering young trees
Salty winds turn leaves brown
Ramorum hits Peak District larches
At this time of year cutting a hedge could risk breaking the law because of nesting birds. Tree Wardens, who are spearheading The Tree Council’s Hedge Tree Campaign, are well placed to encourage a responsible approach to hedge cutting among their neighbours, but it’s important to know what the advice should be.
Tree Council member the RSPB says on its website (www.rspb.org.uk/advice/gardening/planting/hedges/the_law.aspx): “We recommend that cutting hedges and trees is avoided between March and August as this is the main breeding season for nesting birds.” The RSPB goes on to point out: “It is an offence under Section 1 of the Wildlife and Countryside Act of 1981 to intentionally take, damage or destroy the nest of any wild bird while it is in use or being built. It will be an intentional act, for example, if you or your neighbour know there is an active nest in the hedge and still cut the hedge, damaging or destroying the nest in the process.”
To report a wildlife crime, go to www.rspb.org.uk/ourwork/policy/wildbirdslaw/reportform.aspx or contact your local police. Many, though not all, police forces have a dedicated wildlife crime unit.
The Tree Council and some of its member organisations have signed up to the Partnership for Action Against Wildlife Crime (PAW). This is a multi-agency body comprising representatives of the organisations involved in wildlife law enforcement in the UK. It provides opportunities for statutory and non-Government organisations to work together to combat wildlife crime (www.defra.gov.uk/paw).
A new strategy for protecting Britain’s trees and forests from pests and disease was launched in June. The Tree Health Strategy will promote a consistent approach across England, Scotland and Wales. Prepared by the Forestry Commission under the direction of the GB Biosecurity Programme Board, it is a response to the increasing threat to trees and woods from pests and diseases arising from the rapid expansion of global trade and the changing climate.
It is an interim strategy, pending development of an integrated approach to plant health (covering tree and wider plant health) across government. The timing and direction of this will be influenced by EU negotiations on a new plant health regime. Tree and plant health in the UK is subject to European as well as domestic regulation and legislation.
“We need to manage and control the unprecedented threats from pests and diseases which Britain’s trees, woods and forests face,” said forestry minister Jim Paice. “That’s why we’ve commissioned an action plan on tree health and plant biosecurity. The action plan is one part of a whole range of measures we're using to combat the threat of disease to our woodland and forests.”
The strategy identifies three key lines of approach: border controls to prevent pests from entering Britain; moving quickly to eradicate or contain the threat; learning to live with some new pests and diseases, and adapt tree and forest management regimes to reduce the threats they pose.
Information about tree pests and diseases is available at www.forestry.gov.uk/pestsanddiseases
A worrying disease that attacks London planes has been confirmed in the capital. The disease, massaria (Splanchnonema platani), was previously found only in Germany and Holland, says the London Tree Officers Association (www.ltoa.org.uk).
“London planes are generally very disease tolerant. The discovery of the massaria fungi in the UK therefore poses a real threat and presents a huge problem for the specialists that manage the trees,” said Becky Hesch, LTOA executive officer. “It was originally only thought to affect unhealthy trees but has now been found on healthy trees as well. Very little is known about how the disease spreads.”
The fungi can rapidly decay branches so the only solution is to remove any branches that show signs of the infection to prevent them from failing. Currently, there has been no need to remove any entire trees.
Some local authorities are changing their inspection programmes for all London plane trees in high-risk areas. At a time when councils are having to find significant cuts, this disease demands that tree officers undertake more inspections and pruning work, compounding the financial problems for tree managers, points out the LTOA.
In the image (top right photo), the right side of the branch shows decayed deadwood due to the massaria infection and the left half shows live wood.
Tree Wardens are being asked to ‘adopt a tree’ to help compile a register of tree health. TreeWatch, a citizen science project, is being run by Tree Council member the Sylva Foundation in partnership with The Tree Council, EarthWatch, the Royal Horticultural Society and the Forestry Commission. The aim is to compile a register of tree health across the country.
Because keeping track of existing and new threats to trees is expensive – scientists are often overworked and under-funded – Sylva is enlisting the help of volunteers. It asks Tree Wardens to:
• choose any species of tree to adopt – in your garden, in the street, your local park or in the countryside
• go to www.TreeWatch.com to add your tree to the map, and if you can, provide some basic information about it.
Sylva will then invite you to take part in its annual survey of all adopted trees. It also runs specific surveys, for example on horse chestnut leaf miner (the second and third pictures on the right of this page show leaves at different stages of the infestation, as categorised by Sylva for the TreeWatch survey) and European pear rust.
The Sylva Foundation is a tree and forestry charity that aims to revive Britain's wood culture. It has three core programmes covering science, education and forestry.
Despite the recent rain, young trees are not out of the wood yet in terms of water. During the very dry months of this year, The Tree Council has had many enquiries from Tree Wardens and others, worried about the survival of newly planted trees and whether they should water them. Here are some thoughts from Tree Council member organisations about if, when and how to water young trees and how volunteers like Tree Wardens can play an important part.
It takes up to two growing seasons for a newly planted tree’s root system to connect fully with its surrounding soil. During this period, if the soil is dry, watering could mean the difference between survival or not.
There’s no substitute for getting your hands dirty and feeling the soil, not the surface, but 100mm (4 inches) or so deep. If it feels dry, water it – deep, slow and twice weekly during drought periods is best (an evening sprinkle is likely to be useless). As long as you don’t create a swamp, over watering is unlikely.
Wherever possible use ‘grey’ water, even with detergents which act as a wetting agent, or collected rain, rather than from the tap.
Tree Wardens can help by keeping weeds away from newly planted trees. Mulching is the best form of weed control but weed removal is an alternative.
Nick Eden, Director
Watering following transplanting is not only a good idea, it is essential, particularly during the first growing season.
The National Plant Specification recommends watering at fortnightly intervals so that the full rooting depth of the soil is saturated. It is estimated that this will be at least 20 litres of water per application for heavy standard trees and at least 10 litres for small transplants.
The amount of water required will vary considerably according to the texture and structure of the soil. Soils with a low water holding capacity (e.g. sandy soils) will need smaller amounts of water but will have to be watered more frequently.
Tree Wardens can help by monitoring trees and picking out early signs of water related stress and watering the pit surface slowly and steadily on a regular basis.
Keith Sacre, Sales Director
If watered well and mulched well, newly planted trees and hedgerows should be fine.
In the main, tree roots are very successful in seeking available water, making them in turn stronger and more resilient. We haven’t watered our new hedgerow trees at all since they were planted in November 2010.
We have had hardly any rain since early March and they are fruiting well and showing no signs of distress. They were heavily mulched with chippings on top, and I think that has helped.
Fiona Houghton, Project Officer, Kent
Consulting Arborist Society
Watering is important for recently planted trees, especially during dry spells in the spring and summer. Many trees die within two to three years of planting, often through drought. The tree has not developed a network of roots to support it and, when in leaf, can easily dry out.
When watering, provide 50-100 litres depending on conditions, one to four times per month, preferably in the cooler evening. An occasional good soaking encourages deeper roots. More established trees need less. It is an ideal role for Tree Wardens, who can help monitor local trees.
Mark Chester, Chairman
During very dry spells in the first two or three seasons after planting, watering may be necessary to prevent the loss of a sapling.
The ground should be thoroughly soaked so that roots are not encouraged to grow close to the surface. Where possible buried pipe systems which allow watering direct to the roots should be installed when planting – these can often be seen on street trees where a section of pipe protrudes up next to the trunk.
In addition, always try to reduce water loss by methods such as removal of weed growth around the trees and the use of mulching.
Alan Cathersides, Senior Landscape Manager
In woodland/large plantations if you plant two to three-year-old bare rooted trees in the winter dormant season, they shouldn't need any watering unless there is a drought in the first couple of years. (Extensive watering of woodland is impractical.)
For trees planted as larger specimens in gardens, along roadsides, etc, or not bare-rooted in the winter, it should be expected in the first years to water as necessary.
To establish the root system, less frequent, thorough watering should promote deep roots which should encourage the tree to be more drought tolerant.
Michelle Rogers, Tree Nursery Officer
National Association of Tree Officers
Watering newly planted trees during the summer months is a great idea, but can be an expensive business.
NATO believes that most local authorities would welcome help from local volunteer groups or just individual residents. We are, for example, aware of proposals in Norwich to put postcards through the letter boxes of residents adjacent to where new trees have been planted, asking for assistance with watering or to report any damage or vandalism. This seems to us to be a good idea.
David Williams, Administration Officer
Trees are a precious and much-treasured part of our natural heritage. They support a huge array of life, help cool our cities and stabilise our soil. They are also the focus for a huge range of conservation efforts across England.
In very dry conditions such as those we have experienced in recent months, it can make good sense to water newly planted trees. Tree Wardens can have an important role to play here, giving their own time so that we can all enjoy our forests, parks and urban trees for generations to come.
Dr Helen Phillips, Chief Executive
People’s Trust for Endangered Species
Trees should be watered when they are first planted until they are established.
Once established, too much watering encourages root formation near the surface, whereas the tree needs to seek out a consistent water supply lower down.
Anita Burrough and Steve Oram, PTES Orchard team
Small Woods Association
Bare rooted trees, planted in the dormant season, will not need watering in the summer unless the weather has been exceptionally dry.
Pot grown or root balled trees, if planted outside the dormant season, will need to be watered regularly during their first summer unless the weather is wet. It is a good idea to plant such trees so that the level of the soil around the roots forms a shallow bowl to ensure that the water does not run away.
It is vital to reduce competition for water for the first three years by eliminating grass and weeds in a 1m diameter circle around each tree. This can be done by mulching with old carpet, cardboard or compost, or hand weeding.
Volunteers such as Tree Wardens have a useful role here as they are the people ‘on the spot’ and can respond to a period of dry weather by giving newly planted trees a ‘drink’.
Phil Tidey, Membership Services Manager (Policy and Technical)
Trees for Cities
In addition to our regular watering rounds, we encourage local people to get involved in looking after newly planted street trees, near their home or workplace, by watering the trees during dry spells.
A good soaking (about five buckets) right down to the roots every week or two, rather than little and often, encourages root development and helps the tree to establish.
Jane Scott, Street Tree Projects Co-ordinator
The effect of extreme weather has been giving the impression that autumn has come early to some Scottish trees. Experts from Forestry Commission Scotland are blaming the exceptionally strong winds and salt laden sea air of 23 May for scorching the trees and turning them brown. They say that although the trees may look unhealthy, it is hoped that most will recover over time.
Many broadleaved trees and larches have been affected and, to a lesser extent, pine and other conifers. The main area affected stretches from Dumfries and Galloway north to Fort William.
Hugh Clayden, Tree Health policy adviser for Forestry Commission Scotland said: “We are quite sure that what is being reported here is usually a result of the recent very strong winds coupled with salt-laden air on the coast. Basically the trees’ delicate new leaves and needles have been dried out as well as physically damaged by the exceptional winds.”
Browning and leaf wilt is also apparent inland but does not yet appear to be anything like as severe. Other causes of extensive browning include the severe winter frosts.
Ramorum disease of larch trees has been found in Derbyshire’s Peak District. The Forestry Commission has confirmed the disease in Japanese larch trees in a small woodland between Bakewell and Matlock, 80 miles from the nearest previously known outbreak in larch.
The disease, caused by the Phytophthora ramorum pathogen, can kill larch trees within a year of symptoms first being detectable. Japanese larch needles also produce huge quantities of the spores that spread the disease, so the trees must be felled quickly to limit its spread.
Previously the pathogen has been recorded on other plants such as rhododendron and bilberry in South Wales, South West England and parts of the Midlands and North West, including Derbyshire. However on larch trees it has been confined until now mostly to South Wales and South West England, with single isolated sites in central and northern Wales and western Scotland, and a small number in Ireland and Northern Ireland. The Peak District outbreak on larch was first noticed during extensive aerial surveys to spot possible signs of the disease.
Ben Jones, the Forestry Commission’s phytophthora programme manager, reported: “Almost all the other sites that we are most suspicious of at the moment are either close to or contiguous with existing infection sites that were identified in 2009 and 2010. “We are also encouraged that the area of woodland identified from the air that needs follow-up checks is down on last year. However, we cannot afford to be complacent because the dry spring weather might have delayed the onset of symptoms in some areas, so we will remain alert for symptoms emerging for the remainder of the year.”
Since 2009 a contingency plan has been implemented to limit the spread of the disease. This includes licensing and authorisation systems for hauliers and wood-processing plants; protocols setting out measures that can prevent accidental spread of the disease on footwear, clothing, vehicles, machinery, tools, equipment or pets; managing the increased flow of larch timber on to the market in a way that minimises market distortion; providing grants to help affected woodland owners comply with requirements to fell or clear infected trees and to plant replacement trees; and significant advances in scientific understanding of the disease.
Detailed information about P. ramorum is available from the Forestry Commission’s website at www.forestry.gov.uk/pramorum.