Evidence a council needs before approving ash removal

Councils will not consent to the removal of a protected ash on the strength of a photograph and the words "ash dieback". What they need is a written assessment by an arboriculturist that records the crown decline of each tree against a stated scoring system, sets out the target the tree could strike if it failed, gives a considered view on retention or phased reduction as alternatives, and proposes replacement planting. Where the tree is dead or presents an urgent risk of serious harm, the statutory exemptions apply and you notify rather than apply, but you still have to be able to show why.

Ash dieback is caused by the fungus Hymenoscyphus fraxineus and is now widespread. That means tree officers see dozens of these cases and have become sceptical of the ones that arrive without evidence.

Why ash needs a different approach

Two features of the disease drive the process. Decline is progressive and variable between individuals, so a tree at 40 per cent crown loss this year may be at 70 per cent next year or may stabilise. And infected ash becomes brittle in a way that changes how it fails, with basal decay and sudden limb loss making climbing inspection and dismantling more hazardous over time.

That is why councils accept a forward-looking safety case for ash where they would not for other species. It is also why they resist blanket felling: some ash show tolerance, and national guidance encourages retaining apparently tolerant individuals where it is safe to do so.

So the assessment has to hold two things at once. This tree is declining and will need work. That does not automatically mean it comes down this winter.

Assessing crown decline consistently

Use a recognised class system and state which one. The four-class approach used in ash dieback management toolkits scores the proportion of the crown showing dieback:

Some councils specify their own system, so ask before surveying. Whichever is used, record each tree individually with a tag number, stem diameter, crown class, presence of basal lesions or Armillaria, and a photograph from a consistent position. Repeat surveys from the same positions, because the comparison between years is what makes the case.

Survey in leaf. A dormant ash tells you almost nothing about crown condition, and an assessment carried out in January will be questioned.

The safety case and its documentation

Risk is a product of the likelihood of failure and the consequence, and the consequence depends entirely on what is beneath the tree. A class 3 ash over a footpath used hourly is a different proposition from the same tree in the middle of a field.

Document four things for each tree:

1. The target: what is within falling distance, and how often it is occupied.
2. The likelihood of failure: the observed defects, the class, and the part likely to fail.
3. The window: how long the tree can safely be left before reinspection.
4. The alternatives considered: crown reduction, monitored retention, fencing or path diversion, and why each was or was not adopted.

Point four is what most submissions omit, and it is the point the tree officer is looking for. A recognised risk assessment method such as a quantified tree risk approach helps, though the method matters less than showing that a method was used.

Liability sits with the landowner under occupiers' liability, and for trees adjoining a highway the local highway authority has powers under the Highways Act 1980 to require action where a tree is dangerous. Neither displaces the need for consent to work on a protected tree.

Exemptions and their limits

The Town and Country Planning (Tree Preservation) (England) Regulations 2012 exempt certain works from the need for consent, including cutting down a tree that is dead and works urgently necessary to remove an immediate risk of serious harm. For dead trees, five days' written notice to the authority is normally required before the work, and for urgent works the notice follows as soon as practicable.

Three cautions. A declining ash is not a dead ash, and relying on the dead tree exemption on a class 3 tree is the fastest way to a prosecution. The exemption covers the tree, and dismantling to ground level with a stump grind may go beyond it. And where a tree is removed under the exemption, the duty to plant a replacement under section 206 of the Town and Country Planning Act 1990 still applies.

In a conservation area, works to trees above the size threshold need six weeks' notice to the council, which may respond by making an Order. The same evidence supports that notice.

Phased removal and keeping the low-risk stems

Where a group or roadside line is affected, a phased programme is usually more acceptable than clearance, and it spreads the cost. Propose it as a schedule: the trees coming down this season, the trees being reduced, the trees being monitored with a reinspection date, and the trigger that moves a tree from one category to the next.

Retaining monoliths and standing deadwood away from targets is worth proposing where the setting allows. Ash supports many associated species, and standing habitat offsets part of what removal takes away.

Timing brings ecology into it. Bats roost in ash cavities and nesting birds use them from March to August, so a pre-works check, and a bat assessment where roost features are present, has to sit in the programme. Our note on timing tree works around bats and nesting birds sets out the survey windows and the legal position under the Wildlife and Countryside Act 1981.

Volume matters too. Felling above the quarterly volume threshold outside a garden needs a felling licence from the Forestry Commission, and a large roadside programme can exceed it without anyone noticing.

Replacement planting and species choice

Offer replacement planting before the council asks. Councils increasingly want diversity rather than a single substitute species, and the honest answer to "what replaces an ash" is several things, chosen for the site: small-leaved lime, hornbeam, field maple, oak, rowan and hawthorn all do parts of the job an ash did.

State the number, species, stock size, planting season, staking and a three to five year maintenance and replacement commitment. Where planting is secured by condition, replacement planting conditions after tree loss explains how those conditions are worded and discharged.

Keep the survey record. Where a neighbour later claims damage or a council queries a removal, the dated survey and photographs are the only defence, and the same discipline applies to the evidence pack described in tree subsidence claims: evidence a council needs. A structured Tree Survey is the document that holds all of it in one place.

For specialist technical reports, qualified professional input may be required. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.