Tree Health Forum - Spring & Summer 2026
El Niño, ancient trees and hawthorn sampling...
In May 2026, tree health experts from local authorities, research institutions, government and charities gathered for the Spring 2026 Tree Health Operations Forum. The Spring Forum presented an opportunity to discuss tree health preparedness as we approach the summer season, with members sharing knowledge and advice around managing seasonal weather challenges, changing climates, tree health and associated safety risks.
Read on to find out more about what a super El Niño year means for the UK, how experts manage tree safety in areas where the public and ancient trees meet, and how you could get involved with a nationwide citizen science hawthorn sampling programme…
Insights on El Niño from the Met Office
The Forum opened with a Met Office presentation on the potential global weather impacts of a 2026 El Niño event. It is caused by weakening trade winds across the Pacific Ocean, disrupting oceanic and atmospheric circulation patterns. El Niño usually develops in Northern Hemisphere summer, peaking around Christmas. However, by May 2026, Pacific sea surface temperatures were already suggesting a potentially record strength event with temperatures of 2°C above normal or more.
Will the UK be impacted?
The main driver of UK weather is the jet stream, which has low predictability beyond about two weeks, making long-range forecasting a challenge. Nevertheless, influences from around the globe can moderate it to an extent, leading to changes in the likelihood of seeing specific weather patterns. Research shows the main effect of El Niño on the UK occurs in winter and the surrounding months:
November to December: increased probability of milder, wetter, windier conditions.
January to March: increased probability of colder, drier, calmer weather.
June to August: A small influence – if anything a shift towards more unsettled conditions.
It is important to note that these are shifts in probability and it is not possible to state with certainty that “El Niño means X for the UK”. Rather than predicting long-range impacts, the Met Office suggests its 3‑month Outlook for those looking for guidance on UK seasonal trends, as it incorporates El Niño alongside many other climate drivers. The 3-Month Outlook suggests that hot conditions are more than likely for the UK this summer, and the chances of wet and windy conditions are only slightly higher than usual. This provides an indicator of how the levels of weather-related risks for the season ahead compare to normal.
In the context of unsettled weather, the Forum had called previously for advice on tree asset management to support preparedness activities for extreme weather events.
Where trees and people meet
To answer this request, we invited Epping Forest to the Forum to present their approach to managing a complex landscape of 55,000 ancient and veteran trees visited by 13 million people each year. The forest faces pressures including compaction, vandalism, deer browsing, and pests and disease, such as ash dieback, Dutch elm disease, oak processionary moth and powdery mildew.
Epping shared that they use a risk based zoning system, categorising areas by occupancy and consequence into Red+, Red, Amber and Green zones, to dictate how often they are inspected. Staff carry out passive assessments during daily work, while active assessments are completed on a cyclical basis by trained inspectors, storing all information in Abortrack. High-risk areas are also inspected again following storm events. A notable innovation is the use of mobile phone data to map the walking routes of visitors to the site, which has allowed tree managers to build an evidence based heat map of footfall, reporting in real-time which sites need to be looked at more regularly and which can be dropped to a less frequent cycle. A key theme of the management strategy at Epping, is balancing public safety with ecological value including avoiding unnecessary felling and retaining deadwood where appropriate. Importantly, tree risk management should be approached in a proportional way, with staff safety considered when planning interventions to avoid transferring risk.
Focus on the Queen Oak
Our third presenter, Will Jones from The Tree Management Company continued the theme, zooming in to look at how collaborative action sought to protect an individual tree: the (approximately) 650-year-old Queen Oak in the New Forest. Historically overshadowed by the now-dead King Oak, the Queen Oak became a priority after the King Oak declined due to decades of environmental pressures and eventually died after it was continuously pruned to a low monolith.
Two years ago, the Queen Oak developed a major structural crack that threatened imminent failure and, wanting to avoid the same fate as the King Oak, The Tree Management Company, New Forest National Park Authority (NPA), Matt Shute from East Devon Tree Care and Ellingham, Harbridge and Ibsley Parish Council came together to devise a rescue plan. The first stage introduced ‘dragon’s teeth’ surrounding the base of the tree to prevent parking and reduce compaction, followed by the installation of stainless-steel bracing to counteract the splitting of the trunk, alongside halo thinning of neighbouring, younger trees to improve light levels.
The project and its success generated media interest and raised awareness of the importance of ancient tree management, as trees become less resilient to change with age. The failed trunk of the King Oak was left as a display of historical continuity, to create new habitat and as a reminder of the social and ecological importance of preserving veteran trees.
The above case studies provide an insight into the importance of balancing public access and land-use with ecological protection at both the forest-level and for an individual tree. The management required for each varies, but both overlap in the use of collaboration across multiple tree and land managers to reach a shared goal. The interest taken by the Forum in the Epping and Queen Oak case studies underlines the need for functional knowledge-sharing systems that can communicate the wealth of expertise that exists across the sector to those who need it.
Significantly, both prioritised the use of contextual knowledge, where those involved in the development of tree health and safety strategies have a deep understanding of the system they are trying to protect, and all its complexities. This can be seen at Epping, where tree health and associated risks are considered in tandem with maintaining and protecting the ecological value of the forest and at the Queen Oak, where the response was tailored to the needs of the individual tree.
Supporting hawthorn health
The final presentation, from Forest Research introduced its Hawthorn Monitoring Project, looking into hawthorn health, hedgerow resilience, and disease surveillance, supported by specialists from Fera. Hedgerows are central to national environmental targets, with commitments to create or restore 30,000 miles by 2037 and 45,000 miles by 2050. Hawthorn, which makes up around 70% of many hedgerows, is therefore a key species, but their resilience to pests and diseases is poorly understood. The project encourages members of the public to sample hawthorn for the disease Fireblight (Erwinia amylovora) and the fungi Rust (Gymnosporangium spp.), alongside asymptomatic hawthorns to allow researchers to build a clearer picture of pathogen diversity across the UK. For more detailed information on how to take part, please visit our website and view the Hawthorn Sampling Protocol.
Get in touch and share your experience with the Forum
Are you struggling with a tree health issue in your local authority? Are you seeking best practice and advice? Let us know what topics you would like our next Forum to discuss.
Contact us by emailing scienceandresearch@treecouncil.org.uk.
For guidance around tree establishment, monitoring and survival, as well as pests and diseases and seasonal advice, please visit The Tree Council’s Guidance Hub.
Find out more about The Tree Council at treecouncil.org.uk. Sign up to our monthly newsletter The Leaflet, and follow our social accounts: Instagram, TikTok, Facebook, LinkedIn, X/Twitter, YouTube.
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