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Failure of Cercidiphyllum japonicum (Katsura tree), Crighton last week

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An example is COBRA bracing

belts and the stem surrounding cobra system can be used for hollow branches and stems

Load bearing is distributed over the full contact surface.

Shock loading is avoided due to the flexibility of the synthetic fibres.

The creation of reaction wood is not disturbed No drilling - no injury Easy and quick installation (Quick splice) Automatically lined up in the load direction

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Is this bad practice - belt bracing of veteran trees?

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Is this bad practice - belt bracing of veteran trees?

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Belt bracing is often used as a non-invasive static system

However, due to it's static nature, it can strangle the tree

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Bracing installed too high above crotch

Beech tree has ripe wood - poor compartmentalizer

Stem on left too small to support drilling and rod through stem

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Position of cable bracing here would not be recommended - too high in the crown

Preference would be a dynamic system that allows for stem flexure

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When co-dominant stems are closely aligned, then drill holes above the crotch

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Static rods and co-dominant stems with crack (included bark)

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Static rods and co-dominant stems with crack (included bark)

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Check the positioning of the two rods here - directly through crack due to wide angle of branches

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To repair or provide support after failure has occurred or for existing defect

Restricts all movement below the point of the installation

Can allow for wound wood development around installation of co-dominant stems - lack of friction prevents crack migration (elephant's ears)

Different types - Threated rod with eye-nuts (for steel cables) drilled through stem

Without eye nuts for co-dominant stems with included bark) - no steel cables needed

High expertise required - correct positioning and adjustment

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When a tree has an inherent weakness

To extend the lifespan of the tree

To alleviate the need to prune (pruning equals decay)

Reduce risk to people and livestock

There are two types - static and dynamic

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Securing a horizontal branch to prevent damage in the event of failure (EU Guidelines on bracing)

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Location of the dynamic system should be in the upper crown, where there is branch flexure - top 1/2 measured from location of the fork

Location of the static system should be installed in lower 1/3 as close to junction as possible (least flexure)

Consider compartmentalization ability when using static systems

Dynamic and static systems can be installed on same tree

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•LOLER 1998

•PUWER 1998

•RIDDER 95

•Health and Safety at Work  Act 1974 – All stem from this, proving a safe working environment for employees, adequate training of staff etc

•Must write a health and safety policy

•Are NPTC/Lantra certificates a legal requirement?

•Manage of Health and Safety at Work Regulations 1999 – places a duty on employers to assess and manage risks to their employees and others arising from work activities.

•Occupiers Liability Insurance under Occupiers Liability Act 1957

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•6 weeks notice in writing

•Unless less than 75mm in diameter when measured at 1.5m

•Trees are normally inspected during the notification period

•Normally notification goes on a public register

•And in local newspapers

•You can contact the Local Authority for details

•If the tree is Dead, Dying, or Dangerous under the Town and Country Planning Act, then work can be carried out without permission, though generally a quick phone call would suffice, or an email with picture evidence.

•You must place notifications where members of public can read them

•What happens if you don’t follow the procedures?

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Left: large pruning wound, top right: decay extent of bad compartmentalizer, bottom right: extent of decay in strong compartmentalizer 

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•This depends on the species, and whether or not it is a good or strong compartmentaliser

•The rule of thumb is prune to a lateral no less than 1/3 the size of pruned stem or branch

•What about the size of the wound?

•Gilman says the size of the wound should be no greater than 8cm Diameter on poor compartmentalisers

•And approx 12 cm on strong compartmentalisers

•How do you feel about this?

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•Develop or maintain a dominant leader

•Identify lowest branch in the permanent canopy

•Prevent branches below the permanent canopy from growing upright or too large

•Space main braches along a dominant trunk

•Keep all branches less than one-half the trunk diameter (remember Tesco’s)

•Suppress growth on branches with bark inclusions

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Pruning before and after (left), result 5 years later (right)

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•To develop strong tree structure

•Trees without the necessary pruning are susceptible to mechanical failure. Why?

•You must look at the tree’s biology, rather than look at it as a mechanical object!

•So, what about the aspect ratio?

•You shorten stems back to lateral branches that are no less than 1/3 the diameter of the cut stem

•Small aspect ratio versus large aspect ratio?

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•Structural pruning helps the tree to produce on principal leader

•So one trunk

•One must reduce the length of codominant leaders (subordinate)

•In theory, branches on large mature trees should be kept smaller than half the trunk diameter (referred to as aspect racing)

•What are the advantages of the dominant leader structure?

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•Structural pruning is pruning that can be carried out on trees of any age, especially when young, and of moderate age

•There is light structural pruning, and moderate structure pruning, the latter being more aggressive

•Why do shade trees in the urban environment develop such poor weak branches, and untidy crowns?

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What do you think of this practice?

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Shigo refers to tipping as cutting back secondary branches to where there is no nodal point.

Such branches die-back and often die within 2-3 years

Like just cutting a branch in half

Very common practice

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To produce a tree that will be free of defects or weaknesses

Carried out also in order to influence the structure or shape of the tree – i.e. could be pollarding, or crown raising sufficiently for street tree planting

Most importantly, the removal of co-dominant stems – lead to compression forks

Also, removal of crossing branches – to prevent rubbing, disease etc.

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•Removal of dead wood and live wood

•The live wood would include crossing branches, diseased branches, and possible reductions

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•Remove only those branches growing towards the lines – direction pruning

•Maintain a pruning cycle

•Start pruning early in life of tree

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•To provide light or penetration through the tree

•Removal of dead, crossing branches, congested branches, diseased branches

•Even density of foliage

•Avoid cutting branches back to parent stem unless a must

•Why might you carry it out???

•Should not exceed 30% BS3998?/ Where did that come from?

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Very useful with some species that have poor crown development

Young limes and species such as Tibetan Cherry Prunus serrula and

Prunus cerasifera ‘Pissardii’

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•This method reduce the density of the crown  by removing a portion of the secondary and small live branch growth from within the crown

•Shigo and Mattheck claim it to be a bad practice for the tree. I think within reason it is a good method

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Crown raising is simply the act of lifting the crown by removing lower branches between the ground and the canopy

Two types

Stem clearance and height clearance

Where might you do both?

What is  height clearance above say highway and a path?

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Upper branches of tree are removed to allow development of callus on young trees

Old traditional practice – Urban areas – France, Spain etc.

Pruning intervals 2 – 6 years

Live longer than unpollarded trees

Pollards tend to grow slowly – narrow growth rings

Reasons for pollarding?

Trees such as Pyrus calleryana ‘Chanticleer’

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Are both of these pollards?

If not, which is which?

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•This should not be confused with a reduction or topping

•You cannot pollard a mature tree – this is topping

•You can top a mature tree or lapsed pollard and hope to eventually manage it as a pollard

•This is hard

•Pollarding is a traditional form of management

•Should begin when the tree is young

•Debate over ‘lapsed pollards’ – how lapsed are they?

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What does this tell you?

Mast and sail area of tree?

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New growth is emerging from the dormant buds lower down on the crown

There will be much dysfunction here as the new growth will be weak, due to poor attachment and fast growth

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Salix fragilis or the crack willow

This was a major reduction, though technically not a reduction.

There are times when one can consider the extreme or lose the tree

This poplar vigorously put on new growth

It has to be monitored though every two years and cut back periodically

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Can the golden rule be broken? Fine line?

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Can the golden rule be broken? Fine line?

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I ordered this work to be carried out in order for the Church clock to be viewed by people on the high-street again

These lime trees were ‘lapsed pollards’

This is still a form of topping, but I  would like to refer it to a reduction

Lime trees are very tolerant of this

This job was carried out in Spring

Trees have come back well

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1.Reduces food making capacity

2.Stimulated undesirable water sprout growth

3.Leaves large wounds

4.Creates a hazard

5.Injures bark

6.Disfigures the tree – replaces natural beauty and form

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•Topping occurs when the vertical stem (leader) and major scaffold branches on mature trees are cut back to stubs at uniform height.

•

•Also referred to as: stubbing, heading, crowning, dehorning.

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Discuss the 30% limit on a crown reduction BS3998

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Discuss the 30% limit on a crown reduction BS3998

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•Where is the limit?

•Where does it become topping?

•Is there an overlap?

•Is crowning raising a form of crown reduction?

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A crown reduction is  reducing the size of the crown by pruning back to suitable lateral branches

It requires a detailed investigation of the tree – how much to remove, to where can it be removed to (what node)

A good reduction will

•Keep the shape of the tree

•Will not impact too much on a tree’s health

•Will not be a future hazard

•Will not produce ‘water shoots’

•

Not to be confused with topping

Consider if you have Ganaderma on a large oak? What do you do? Remove or reduce?

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1.When you ridge is evident exactly between the two stems, then either stem could be removed.

down to your experience

Point E is the beginning of the stem bark ridge

2. You can see where the crack (included bark) has formed between the two stems

The bottom of the crack here is a guide to where you would have your bottom cut

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Proper versus improper of co-dominant stems

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Proper versus improper of co-dominant stems

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Here, the red lines guide you as to the direction you should take when pruning.

What do you notice with these two examples??

What is missing??

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Proper and improper pruning of co-dominant stems

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Proper and improper pruning of co-dominant stems

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What is happening here?

Is this an easy mistake to make?

How many of you have made it?

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•This here is a correct pruning cut

•It is easy to think that it may not be the correct option, as the surface area of the would appears larger than if cutting it horizontally

•Note the branch bark ridge!

•Do not cut into this ridge, or behind it

•Use the ridge to guide your cut

•Note that there is no branch collar to guide you

•Use the bottom white arrow and then move out, this is the guide for the bottom of your cut

•Best time to carry out this pruning is during the tree’s formative years

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The branch collar or TPZ (tree protection zone)

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The branch collar or TPZ (tree protection zone)

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•Consists of overlapping fibres

•Clear swelling between at branch/stem junction

•Overlapping fibres between stem and branch wood

•This area is highly resistant to the ingress of fungi

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•Natural Target Pruning

•How many of you are now familiar with this?

•Who pioneered it?

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•Reduction

•Crown-raising

•Pollarding

•Coppicing

•Thinning

•Crown clean

•Drop-crotching

•Retrenchment

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•Dynamic mass versus static mass – core skin hypothesis

•Potential energy versus kinetic energy

•Energy available  (potential) versus energy required (kinetic)

• As a tree gets older its ratio of potential to kinetic energy changes

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Above is the Core – skin hypothesis

How much should be removed

(L) Live wood

(D) Deadwood

Trees are young – more living wood can be removed

When trees are old more deadwood can be removed

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Cutler and Richardson, 1989. Tree roots and buildings

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When is the best time of the year to prune? Depends?

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When is the best time of the year to prune? Depends?

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There are many factors involved when considering when to prune

Light pruning (pictures to left) could be carried out at any time of the year, though preferably not autumn

Consider the species you are pruning i.e. some species are more tolerant than others

E.G. oak, lime, and plane are more tolerant to severe pruning than beech, birch, honey locust

Poplar and willow?

Age of the tree

Young trees tolerate more severe pruning than older trees

Veteran trees require very special attention, as these do not have the same available energy resources as younger trees

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•‘nice to do’s’ – remember, you have a budget!

•If you’re a contractor, then you have an ethical obligation for a tree’s health

•Bird droppings

•Leaf litter

•Honeydew

•Flower litter

•Interference with aerials, satellite dishes

•Because they (member of public) don’t like the way it looks

Can you think of any more?

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This would be justifiable pruning!

Ensure pruning is carried out to a reasonable degree

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•Dead, dying, dangerous

•Obstruction

•Legal nuisance – actionable by law

•Physical contact with building and roofs

•Physical contact with wall or fence of property

•Formative pruning

•Where trees are restricting repairs of property

•Overhanging small garden – light levels?

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•The wrong species in the wrong place - design

•For aesthetics – we like things to look tidy!!

•For people’s safety – minimising risk

•For a tree’s health – pruning can be good J

•Because there is pressure on us to do so!! – tree officer and members of public

Pruning should be the last alternative

Develop your principles on tree management prior to planting trees and when trees are young!

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•Working in groups, I want you to name as many words as possible associated with pruning – mind map!

•This will expose you to the terminology through collective thinking

•Many of you have worked around the world: what terminology do they use there?

•Different counties in the UK often use different words to describe pruning

Words include, crown raise, reduction etc.

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•Is there ever a time when topping can be justified?

•Shigo claims it is a crime against nature!

•Wall 4 – new wood outside dysfunctional core

•Species? CODIT

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Discuss the 30% limit on a crown reduction BS3998

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Discuss the 30% limit on a crown reduction BS3998

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•Form groups

•

•What is a crown reduction?

•How different is a crown reduction to topping?

•Is there an overlap

•Discuss species.

•Is thinning or crown raising a type of crown reduction?

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Pruning young trees - higher symplast-apoplast ratio

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Extent of damage from improper pruning

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Wall 1 of the CODIT - the branch collar

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•Where are they acceptable?

•Once pruning, does it require any further action?

•Consider age of tree.

•Species?