Pruning specifications councils will condition

A tree pruning specification that says "reduce by 30 per cent" will be refused or returned, because nobody can tell from it what the tree will look like afterwards or whether the work is reasonable. Councils condition pruning in the language of BS 3998:2010, the British Standard for tree work, which specifies operations by the dimensions of the crown that remains rather than by the proportion removed. Get that right and a tree officer can approve the work in one pass.

The same applies to applications for consent to work on a protected tree. Vague descriptions produce refusals, requests for further information, or consents so tightly drawn that the contractor cannot do what you wanted.

Why vague descriptions fail

A percentage reduction is ambiguous in three ways. It is unclear whether the percentage refers to crown volume, crown spread, branch length or foliage mass. It gives the tree officer nothing to assess the arboricultural effect against. And it gives the contractor latitude, which usually means more is taken off than intended.

There is an enforcement dimension too. If the consent says "reduce by 30 per cent" and a neighbour complains that the tree has been butchered, nobody can prove what was authorised. A consent specifying final crown dimensions can be checked against the tree.

Officers also read a vague specification as a sign that no arboriculturist was involved. That tends to produce more scrutiny of the whole application, not less.

The operations, defined

BS 3998 sets out standard operations and how each should be described. The differences between them matter, because clients and contractors use the words loosely.

Thinning is the one operation where a percentage is the correct unit, because the point is to remove a share of the secondary growth while leaving the crown's shape and dimensions intact. For reduction, the standard expects you to state what remains.

Avoid the old vocabulary. Lopping and topping are not operations in the standard, and using them signals that the work has not been specified by anyone with current training.

Specifying by measurement rather than proportion

The practical method is to describe the finished tree.

For a crown lift: "crown lift to 5.2 m above ground level on the highway side, to the nearest suitable growth point". For a reduction: "reduce height from approximately 14 m to 11.5 m and lateral spread on the south elevation from 7 m to 5.5 m, to suitable growth points, retaining a natural outline". For branch removal: "remove the lowest east-facing limb at the branch collar, as marked on the attached photograph".

Three qualifiers make the specification workable on site. Reference to suitable growth points, because cutting to a node allows the tree to respond rather than leaving a stub. A statement that the natural form is to be retained, which prevents a reduction becoming a topping. And a tolerance, usually expressed as a stated allowance either way, because a tree is not a machined component.

The reference to the tree must also be unambiguous. Use the tag numbers from the tree survey and a plan showing each tree, and keep the numbering consistent with any arboricultural impact assessment already submitted. Renumbering between documents is a reliable way to generate a holding objection.

What the standard expects beyond dimensions

BS 3998 covers more than cut positions. Three of its expectations come up repeatedly in conditions.

Cuts should be made at a suitable position relative to the branch collar, without leaving stubs and without flush cuts into the collar itself. Wound paints and sealants are not recommended. And the amount of live growth removed in one operation should be limited, with the standard treating heavy reductions as a stress on the tree rather than a neutral act.

That last point explains why officers resist large reductions on mature trees. The honest advice to a client who wants a tree substantially smaller is often that the species is wrong for the position, and a staged reduction over successive cycles, or replacement with a smaller species, will produce a better result than one severe cut.

Pollarding and veteran trees

Pollarding is a management system, not a single operation. Re-pollarding a tree that already has established pollard heads is routine and uncontroversial, and the specification simply refers to the existing points and the cycle.

Starting a new pollard on a mature tree is a different matter. It removes a large proportion of the crown at once, creates large wounds on older wood, and commits the owner to a maintenance cycle indefinitely. Councils resist it on amenity trees and will usually refuse it on a tree protected by an order unless there is a sound reason.

Veteran trees need the opposite approach. The objective is retrenchment and retention of habitat features: reducing the crown gradually to reduce loading, retaining deadwood where it is safe to do so, and avoiding tidying. Specifications for veteran trees should be written by an arboriculturist with experience of them, and professional review before submission is strongly advised.

Timing, cycles and wildlife

Timing constraints come from two directions.

Wildlife law is the hard constraint. It is an offence under the Wildlife and Countryside Act 1981 to damage or destroy the nest of a wild bird while in use or being built, so work between March and August needs a nesting check immediately beforehand. Bats roost in cavities, splits and loose bark, and where features are present a survey by a suitably licensed ecologist is required before work proceeds, because a bat roost is protected whether or not bats are present at the time.

Species biology is the softer constraint. Cherries and plums are pruned in summer rather than winter to reduce silver leaf infection. Birches and maples bleed heavily if cut in late winter and early spring. Most broadleaves tolerate work in the dormant season, and formative pruning of young trees is best done little and often.

Cycles belong in the specification where the work is recurring. Re-pollarding every few years, crown lifting on a highway as the tree grows, and hedge management on a defined rotation are all easier to secure as a stated cycle than as a one-off consent that has to be reapplied for.

Getting the specification into the application

Where the tree is protected by a tree preservation order, you apply for consent under the Town and Country Planning (Tree Preservation) (England) Regulations 2012. In a conservation area you give the authority six weeks' notice under section 211 of the Town and Country Planning Act 1990. Dead trees carry an exemption with a notice requirement, and work to remove an immediate risk is exempt but should be documented with photographs.

Submit a schedule of works by tree number, a plan, the reason for each operation, and photographs for anything described by reference to a specific limb. Where pruning is required by a planning condition rather than sought by the owner, check that the condition and any separate order consent are compatible, a conflict examined in our note on when a planning condition and a TPO consent collide. If the application is refused, the quality of the original specification is what the appeal turns on, as discussed in our note on arboricultural evidence at appeal.

This is general guidance rather than legal advice. Check the position with your local planning authority or a qualified arboriculturist before carrying out work on a protected tree, because unauthorised work is a criminal offence.

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