Pruning Pruning shall be defined as the removal of living or dead parts of a tree. Such parts may be soft growth (epicormic or sucker growth), twigs, branches, limbs, parts of the trees trunk or parts of the root system. The cut material may therefore be of variable size.
Pruning may be undertaken with hand tools or power tools. Material might need to be removed in sections to take into account of adjacent hazards. Arisings may be allowed to fall to the ground or they may be guided to the ground, by hand or by slinging a rope.
When arisings are specified to remain on site, logs shall be stacked neatly and woodchip is to be spread evenly over the indicated area unless specified to be left in piles.
No tree should be pruned without first establishing clearly defined pruning objectives, which may include the following:
This list is not exclusive and will vary depending on the tree itself and the surrounding land use, but the methods used to achieve them can be selected from the following pruning systems;
Formative Pruning Formative pruning shall be defined as the pruning of a tree in its youth to result in an appearance considered typical for the species or variety of tree concerned.
The aim of formative pruning is to produce a clean stemmed tree and to promote the establishment of a strong branch structure and balanced crown. As the tree reaches maturity it should be free from major structural defects, unwanted secondary leading shoots, potentially weak forks and crossing branches.
Where a young tree is still staked/tied, broken stakes and ties will need to be replaced/adjusted or completely removed if the young tree is of sufficient size to support itself.
No more than 20-25% of the live crown shall ever be removed as part of a single pruning operation.
Crown Clean Crown clean is the removal of dead, dying or diseased branches. This Includes the removal of broken branches or stubs left from previous tree surgery operations, and the removal of all unwanted objects, e.g. rope swings, tree houses, wind-blown rubbish from the tree. Other objects such as wires or boards should also be removed without causing undue damage on the tree concerned.
Crown Thin Crown thinning is defined as the removal of a small proportion of live woody growth from the crown of the tree to produce an even canopy of foliage on a well balanced structural form of a tree that is typical of the species or variety of the tree concerned, with an aim to reduce the density of the foliage without greatly altering the shape of the tree as to reduce the wind resistance thereby increasing stability. The process will be achieved by firstly completing a crown clean and then reducing the foliage amount by the stated percentage.
Crown thinning can cause vigorous growth in some species, causing weak and potentially dangerous branches to form and grow from pruning points.
Crown Lift Crown lift is defined as removal of branches that extend below a specified height. Statutory heights are defined as 2.5m over footpaths and 5.0m over highways. Resultant canopy base might therefore be stepped to allow for different clearances.
Crown Reduction The reduction in height and/or spread of the crown (the foliage bearing portions) of a tree.
Crown reduction may be used to reduce mechanical stress on individual branches or the whole tree, make the tree more suited to its immediate environment or to reduce the effects of shading and light loss, etc.
The final result should retain the main framework of the crown, and so a significant proportion of the leaf bearing structure, and leave a similar, although smaller outline, and not necessarily achieve symmetry for its own sake.
The point of pruning should be made back to an acceptable branch, twig or bud. All soft growth (epicormic) shall be removed from the trees trunk.
Not all species are suitable for this treatment and crown reduction should not be confused with ‘topping’, an indiscriminate and harmful treatment.
In certain situations the Instructing Officer may direct that the silhouette (or the extent of the crown in one direction) be atypical because of location targets and considerations.
Part Crown Reduction Part crown reduction is defined as reduction of the overall size of the outline of one dimension of the canopy, from the tips of branches/limbs towards the main trunk. The point of pruning should be made back to an acceptable branch, twig or bud. All soft growth (epicormic) shall be removed from the trees trunk.
The majority of broadleaved species can only withstand crown reduction works on a number of occasions because removal of too much live foliage will inhibit the trees ability for future growth.
Conservation pruning Conservation pruning shall be defined as pruning a tree to retain or create new features that will be desirable for a wildlife habitat. In such cases it may be considered advantageous to create large wounds with the aim of increasing the area of dead and decaying wood in a tree or to top a limb to encourage a crown of dense re-growth which could provide good nesting opportunities for birds.
The retention of dead wood around the crown of a tree may be considered an important aspect of trees managed for their wildlife value. However, there are often conflicts that arise when health and safety issues have to be addressed. In these situations a specification that allows for the sympathetic reduction of dead branches or stems, using cutting techniques like ‘coronet cuts’ to maintain a more natural appearance to the cut ends, may be considered desirable.
Pollarding and Re-pollarding Pollarding is the initial removal of the top of a young tree by removing the main leader or stem to encourage multistem branching from that point. Cutting on a regular basis (Bolling) back to the same point (Pollard Head) on all occasions is required one started. Where pollarding is specified it should be part of a long term management plan for a tree or tree population.
Complete Tree Maintenance Complete tree maintenance shall be defined as a multitude of pruning operations completed so that the tree is left in a safe and sound condition given the location.
Complete tree maintenance shall include a crown clean, a crown lift and a crown thin as specified in paragraphs above. This pruning work shall aim to last for approximately a 3 year period, allowing a cyclical management of the tree stock to be implemented and sustained.
Other Tree Work Operations
Final Pruning Cut Final Pruning cuts should be made at a fork or main stem, where the branch collar can be detected, the final pruning cut should be made back to, but not into the branch collar. When the branch collar cannot be discerned the angle of the final pruning cut should mirror that of the branch bark ridge. Where a limb, branch or leader is to be shortened it shall be cut back cleanly to a side branch finishing with a sloping cut leaving the branch bark ridge and collar intact. The final cut wound surface should be smooth and sound and the cut should have been executed in continuous movement. Surrounding tissue should not have been damaged during any part of the cutting movement.
Specific Branch Removal Specific branch removal shall be defined as the removal of one branch or branches to achieve a specific or desired effect and/or clearance from a potential target. Specific branch removal may also be specified to alleviate risk of branch failure or to clean up and remove broken/hanging branches. A specific branch removal will always be followed by the Final Pruning Cut.
Remove Fallen Branch Remove fallen branch shall be defined as removing branches that have broken cleanly from the tree and climbing operations are not required to retrieve the fallen branch.
Clean up Branch Stub Clean up Branch Stub shall be defined as carrying out the Final Pruning Cut to clean up the branch stub left from broken branches or from previous pruning operations.
Remove Fallen Tree Remove fallen tree shall be defined as removing a fallen tree that has failed and climbing operations are not required to undertaken the work. The stump shall be left at 1m above ground level or as near to 1m as practically possible unless specified by the Arboriculture Officer.
Ivy Ivy will be removed from trees as specified by the Arboriculture Officer to allow full tree inspection to be carried out. Ivy can hide decay cavities or weak unions within the structure of the tree.
Complete removal of Ivy when it is established throughout the tree is often an unnecessary task therefore in this instance the severance of Ivy will be instructed and will include cutting every stem of Ivy at the tree base, and removing a block section of approximately 0.5m of the Ivy. This will kill the Ivy above allowing the leaves to brown and fall off.
Remove Epicormic Growth Remove epicormic growth shall be defined as removing the lower epicormic shoots from the main stem to the height of the first break within the crown of the tree/lowest branch.
Tree Felling Tree felling is defined as the entire removal of a tree to leave a stump at 1m above ground level or as near to 1m as practically possible unless specified by the Arboriculture Officer.
Tree felling works should be carried out in such a way as not to endanger persons or property. Felling in confined spaces or near to adjacent hazards may require a tree to be dismantled.
Removal of Foreign Object The removal an object from the canopy of a tree i.e. tree swing.
Aerial Inspection An inspection of a specific defect within a tree. This inspection will include the taking of photographs.
Stump Removal When stump removal method has been instructed with associated with felling works, the stump shall be removed within one month of the tree felling unless otherwise instructed by the Arboriculture Officer.
Stump Grinding The contractor shall use the necessary machinery to grind out the stump in its entirety. The contractor must ensure that all health and safety regulations are adhered to during this process.
The contractors are responsible for locating existing underground services and ensure that they are not damaged during the stump grinding process.
Treatment Stump treatment is defined as applying the appropriate chemical to the final cut wound surface. Chemicals shall be applied to stumps as specified by the Arboriculture Officer.
The required certificates will be held by the contractor to perform stump treatment process.