Ash dieback: managing ash woodlands with continuous cover and species diversification

Managing ash in woodlands (silviculture): continuous cover and species diversification in ash-dominated stands

Ash dieback is real, but clear felling is not the only answer. In the North West, where wet summers, clay soils and roadside belts are the norm, you can keep a canopy, reduce risk and rebuild diversity in phases. This guide shows how.

What is ash dieback?

A fungal disease caused by Hymenoscyphus fraxineus. It leads to blackened leaves and shoots, diamond-shaped lesions on twigs and stems, and a thinning crown over time (Forest Research). In August you see it most clearly. Forest Research

Ash dieback symptoms — what does it look like?

Leaves and shoots. Wilting and blackening mid-summer; shrivelled leaves may hang on. Lesions. Diamond shapes at leaf scars and branch collars; inner bark shows grey-brown discolouration if you lift a small patch. Crown. Thin, tufted look, with bare twigs and lower epicormic shoots (RHS; Woodland Trust). RHS+1

Season tip: Survey from July to September so autumn colour does not confuse what you are seeing (Forest Research). Forest Research

Lookalikes to check: drought, honey fungus, ash sawfly. If in doubt, get a professional survey (Tree Council). The Tree Council

Two things you can try today:

• Take a smartphone photo in August from the same spot you used last summer; compare crown density.
• Check last year’s twig nodes for diamond-shaped lesions; photograph with a ruler for scale.

If you see this over a play area or bridleway, book a survey.

Continuous cover: why it suits the North West

Continuous cover forestry holds a living canopy while you thin and regenerate in small patches. It suits clay and exposure because it avoids sudden windthrow risk and keeps conditions kinder for young trees. Government guidance highlights continuous cover as a resilient, nature-friendly approach that builds structure and species diversity over time (Forest Research; GOV.UK). Forest Research+1

Pros: keeps shelter; protects soils; phases cost and access on wet tracks; builds resilience.
Cons: needs regular attention; slower timber volumes; requires browse control.

If your woodland borders a road, plan selective work with proper traffic management.

Species diversification for ash-dominated stands

There is no single “ash replacement”. In the North West we typically use mixtures that match ground and exposure:

• Alder for wet pockets and ride edges.
• Birch as a light pioneer to occupy gaps quickly.
• Oak on slightly drier knolls for long-term structure.
• Rowan and field maple for wildlife and mid-storey.
• Sycamore where present — manage to prevent monoculture.
• Disease-resistant elm where available.

Owner guidance stresses diversity and “right tree, right place”. A mixed palette beats a one-for-one swap (Tree Council; Woodland Trust). The Tree Council+1

Operational moves that work:

• Retain the best ash where safe. Young generations are showing encouraging resistance signals; keeping good seed trees preserves genetics (Kew / Queen Mary University of London, 2025). Kew Gardens
• Create small gaps — for example, 0.05–0.15 hectares — on leeward edges to establish cohorts without shock exposure (Forest Research). Forest Research
• Protect from deer with guards or fencing; without it, your new mix will vanish.
• Underplant in shelter; infill with light demanders at the next entry.

If a gap opens near a path, retain deadwood away from routes and sign works while open.

Your 12–24 month plan (simple steps)

1. Late-summer survey. Photograph crowns and stems; map trees along rights of way and access tracks (Forest Research). Forest Research
2. Triage. Mark trees with heavy crown loss or basal lesions near targets for early action; tag better trees for retention under monitoring (Woodland Trust). Woodland Trust
3. Permissions. In England, you can fell up to 5 cubic metres in a calendar quarter without a licence, with no more than 2 cubic metres sold. Larger works generally need a felling licence. For trees under a Tree Preservation Order or in a conservation area, you must apply first (GOV.UK). GOV.UK+1
4. First continuous cover entry. Light thinning; create one or two micro-gaps; plant or protect natural regeneration; manage sycamore if dominant (GOV.UK CCF). GOV.UK
5. Monitor. Re-photograph next August; widen or shift gaps only where establishment is taking.

If you are unsure about felling permissions or Tree Preservation Orders, ask us before you cut.

Two grounded examples

A South Manchester garden. A mature ash over a play area showed a thin crown and a clean diamond lesion at shoulder height. We used a mobile platform for selective crown work, marked it for annual late-summer checks, and kept the area open. Twelve months later, photos showed no further crown loss.

A Bolton woodland edge. Three hectares on clay beside a bridleway. We retained ten of the best ash as potential tolerant seed trees, removed the worst leaners towards the ride, cut three 0.1-hectare gaps, fenced for deer, and planted rowan and small-leaved lime in the two most sheltered gaps while letting birch and alder colonise the third. A second, light entry is planned in three years.

If your site has similar clay and public access, this approach keeps risk down and options open.

Safety, law and good sense

Tree work on brittle ash is specialist. The Health and Safety Executive stresses planning for public safety; mechanised systems or platforms are often safer than climbing in advanced dieback. Choose competent professionals. For permissions, follow the felling licence thresholds and check Tree Preservation Orders through your local authority. Unlawful work can attract heavy penalties (HSE; GOV.UK). GOV.UK+3HSE+3West Lothian Council+3

If in doubt, we will confirm the legal route before works start.

TL;DR

• Photograph in August; compare to last year.
• Look for blackened leaves, diamond lesions, thinning crowns.
• Keep a canopy; make small gaps; diversify to fit clay, wet and coastal conditions.
• Retain the best ash where safe; remove high-risk trees near roads and paths.
• Get permissions right before any felling.

Ready for a plan? If you are in Greater Manchester, Merseyside, Lancashire or Cheshire, book an ash dieback survey and continuous cover plan with Tree Surveys North West today.

Citations: Forest Research; GOV.UK; Woodland Trust; Tree Council; Bartlett Tree Experts; RBG Kew / Queen Mary University of London (Science, 2025). Kew Gardens+5Forest Research+5GOV.UK+5

Short legal note: Works to protected trees and most woodland operations can require consent. Safety-critical trees must be assessed on site by a competent person. We confirm permissions before works. GOV.UK+1