A sudden surge in honey fungus across the UK is being linked to this year’s unusual weather patterns, according to scientists.
Sightings of the golden mushroom — which can attack and eventually kill trees — have risen by almost 200% compared with the same period last year, based on data from the biodiversity platform iNaturalist.
Honey fungus is the common name for several closely related Armillaria species.
The visible mushrooms form temporary clusters in gardens and woodlands, but experts say the real destructive power lies beneath the surface. The main body of the organism grows underground as mycelium, spreading through soil and wood in search of nutrients and dominance over other organisms. Honey fungus is also able to expand through black root-like strands called rhizomorphs, which act as transport pathways and help the fungus invade tree roots and bark more effectively.
The Royal Horticultural Society (RHS) has warned that honey fungus remains the UK’s most commonly reported plant disease. The organisation has been receiving photographs and reports earlier in the year than usual. The species responsible for the most severe damage, Armillaria mellea, can block the tissues that allow plants to take up water. Once this happens, the plant eventually dies back above ground.
Scientists believe the recent hot, dry summer placed many plants under stress — making them more vulnerable to such infections.
This was followed by a warm, wet autumn, which created ideal conditions for mushroom growth and spore release.
Early findings from RHS research suggest that the spread of spores may play a bigger role in transmission than previously assumed, alongside root contact or direct spread through rhizomorphs.
Beyond private gardens, experts are raising concerns about what this surge may indicate about Britain’s shifting climate.
Fungi are crucial to wider ecosystems, providing food for invertebrates and other animals. Researchers say changes in fruiting patterns over the past two decades are increasingly tied to climate change. The spike in honey fungus is being interpreted as part of this larger picture — a sign of how drought, extreme heat, and poor land-management practices are placing additional stress on trees.
Specialists argue that further research on Armillaria biology, ecology, and mitigation is necessary to understand how to limit damage in the coming years, especially as climate extremes become more frequent.