UK trees flower six months early in mild autumn, raising concern for pollinators

Trees in the UK are experiencing an early spring because of mild autumn temperatures, with experts warning this could cause long-term harm to pollinators.

Last month was warmer than average across all parts of the UK, with October marking the ninth consecutive month with above-average mean temperatures.

Chris Nichols, head of conservation outcomes at the Woodland Trust, said the mild weather this autumn meant horse chestnut trees were flowering and showing signs of next year's spring growth more than six months early.

During the extreme heat this summer, many trees underwent an early autumn, wilting and losing their leaves prematurely. Experts said England's ancient oak trees were dying as a result of high temperatures and drought, as trees and ecosystems struggle to adapt fast enough to the changing climate.

Nichols said everything was out of sync, adding that the early spring was particularly concerning for pollinators. Trees need to flower at a certain time of year so they are in sync with insects, he said, calling it an ecological mismatch that raised concerns about the long-term resilience of trees.

Dr Kate Lewthwaite, a citizen science manager at the Woodland Trust, said trees flowering early was a sign of stress. She suspected drought had prompted the trees to shut down essential systems, similar to what happens in winter, and that when the rains came, it encouraged them to start spring flowering out of season.

Lewthwaite said the whole tree may die or be forced to resprout from dormant buds on the trunk or branches, making the canopy much smaller next year. She called for action to help woods become more resilient, such as rewetting woodland and slowing the flow of rain.

Kevin Martin, head of tree collections at Kew Gardens, said trees at Kew's arboretum were also going into early spring. He said the trees had been so stressed this summer that they went into dormancy, and with the warm mild conditions they were now going back into growth, which means they will not have those buds again in the spring.

Martin said the true impact will not be known until spring 2028. He said trees had put on very little growth this year, especially in the south-east where the drought had been really significant, and that weakened trees had led to more failures during storms.