Most ash trees in the UK will show some sign of this disease. That doesn't mean every one needs to come down, but it does mean you need a plan.
Ash dieback is a fungal disease that has been spreading through the UK's ash trees since it was first identified here in 2012, though research suggests it was present from at least 2005. It's expected that most ash trees will eventually show symptoms, though not all will die, some have genetic tolerance and will survive, others are in locations where they largely escape the worst effects.
As a landowner, that puts you in a specific position: you're not expected to remove every infected ash, but you are legally responsible for the risk any tree on your land poses to people who could be affected by it, so infected ash near roads, footpaths, gardens or buildings needs a proper look.
The disease is caused by a fungus, Hymenoscyphus fraxineus, native to eastern Asia, affecting common ash (Fraxinus excelsior) and other ash species. There is currently no cure and no reliable way to stop it spreading once it's established in an area. It typically shows as blackened, wilting leaves, dieback in the crown working inward from the shoot tips, and diamond-shaped lesions where branches meet the trunk. Over time, repeated dieback and decay at the base and roots make a tree structurally unreliable, which is the real safety concern, not the disease itself.
Whoever owns the land a tree stands on is legally responsible for the health and safety of anyone who could be affected by it. If you manage ash near a road, railway, footpath, building or other publicly accessible land, current guidance is clear that you should carry out a risk assessment, infection alone isn't the trigger, exposure is. A tree with early-stage dieback in a back corner of a field is a different question to one leaning over a footpath.
Infection isn't automatic proof of danger. A diseased ash isn't automatically a dead or dangerous one in the eyes of the law, condition and location decide that, not the diagnosis. Don't assume every infected tree is exempt from normal protections, or that removal is your only option.
Ash dieback doesn't override existing protections. If the tree has a Tree Preservation Order or sits in a Conservation Area, those rules still apply in full, see our guide to TPOs and Conservation Areas for how that works. Separately, felling growing trees generally needs a felling licence from the Forestry Commission under the Forestry Act 1967, but most private landowners never hit that requirement in practice: you can fell up to 5 cubic metres of timber per calendar quarter without a licence (dropping to 2 cubic metres if any of it is sold), and garden trees are also normally exempt. Dead trees, or ones posing a real and immediate danger, are exempt regardless of volume. Where none of these apply, or the tree is in a TPO or Conservation Area, get the licence or consent confirmed before the chainsaw starts, not after, it's your job to prove an exemption applies, not the Forestry Commission's.
Current guidance from Defra, the Forestry Commission and the Tree Council favours a measured, risk-led response over blanket felling:
Trees that look healthier than others nearby may have genetic tolerance, retaining them, where it's safe to do so, helps the next generation of ash survive.
Standing deadwood and low-risk dead or dying trees left in place provide valuable habitat, ash supports well over a thousand associated species.
Where a tree is a genuine risk, reduction or removal is prioritised by exposure, high-use areas near roads, paths and buildings first, not by infection level alone.
Regular inspection matters more than a one-off verdict, ash dieback progresses over years, and a tree that's safe today may not be in two years' time. A recorded, repeated inspection is also your evidence that you've acted on your duty of care.
We survey ash trees for signs and severity of dieback, assess the actual risk they pose given their location, and advise on whether that means monitoring, reduction or felling, plus what permissions or licences apply before any work starts.
Sources: gov.uk, "Managing ash dieback in England" (Defra/Forestry Commission, last updated January 2025); the Tree Council, Defra and Forestry Commission's "Ash Dieback: A Guide for Tree Owners"; Forest Research's Chalara management guidance.
This guide is general information, not legal advice. Always get a professional risk assessment for your specific trees and confirm the current position with your local planning authority and the Forestry Commission before carrying out any work.
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