After a cold winter and a late spring, autumn could also be delayed this year with berries ripening and leaves turning later than usual, British wildlife experts said.
According to information gathered by the Woodland Trust’s Nature’s Calendar, plants such as brambles or blackberries appear to have been hit by the cold winter and are fruiting later this year.
Records of ripe berries are a good indicator of the arrival of poet John Keats’s “season of mist and mellow fruitfulness”.
Sightings of the first ripe berries in the countryside have peaked on around August 4 over the last five years, but this year Nature’s Calendar has so far very few records, suggesting autumn is delayed.
By this time last year, the Woodland Trust had more than 1,000 records of the first ripe bramble fruits, with reports peaking on August 2.
But this year the survey, which feeds into records dating back to the 1700s and studies the timings of common seasonal events, has so far received just 81 records, with most in the south and none further north than Leeds.
Rowan berries are also late fruiting, with just 44 records for first fruit compared to 808 by the same time last year, project manager Kate Lewthwaite said.
And hawthorns came into leaf and flowered late because of the cold winter – and are now expected to fruit late as well.
“Seeing as the average – the most observations – is around August 4 for first fruit over the past five years, then considering that we are already at that date and have very few records, it is apparent that autumn could be late this year, just how late we won’t know until the end of the season,” she said.
“Flowering was delayed in many species due to the coldest winter for 30 years and this has a knock-on effect on fruiting.
“We’re some way behind with lots of unripe fruit still on the bushes, and the best still to come,” she said.
And it is not just the berries which are indicating autumn is late this year, Nature’s Calendar results suggest.
Just two records have been received of the first beech leaves to turn – generally the first trees whose leaves begin to change colour – compared to 116 at the same time last year.
Wildlife watchers have seen a trend of leaves turning and falling later over the past few decades as the climate changes.
While Victorian meteorologists considered the season to begin on September 1, the familiar golden hues of autumn are now not developing until the end of the month, the Woodland Trust said.
Trees will not be in their full autumn colours until the end of September or early October and oak leaves are not falling until the end of October – a week later than they were 30 years ago.
“What we’ve found in the last 30 years with climate change, the growing season for lots of species has extended and – leaving this year aside – things are coming out earlier and leaves are hanging around on trees later.
“As long as it is still warm and there is plenty of water there is no reason for trees to start packing up for the winter,” Dr Lewthwaite said.
But in some areas the dry summer has caused trees to turn early, in what she describ-ed as a “false autumn”, particularly street trees in cities. Other signs the climate is changing include people in some milder parts of the UK reporting their grass is growing all year round.
The Woodland Trust is also asking people to report sightings of swifts in the second half of this month.