Autumn could be arriving later this year, experts said after receiving fewer reports of ripe berries and turning leaves than by the same time last year.
The Woodland Trust's Nature's Calendar project, which gathers records of the changing seasons from members of the public, has received far fewer sightings of ripe blackthorn, bramble and elderberries so far this year than in 2011.
Sightings of ripe brambles and blackthorn are both down around four-fifths on this time last year.
There have been just 17 reports of beech trees beginning to change colour, compared to 302 for the same time last year, and only six reports of the first tinting of oak leaves, down from 125 at this point in 2011.
Silver birches also appear to be turning later, with 35 reports of leaves beginning to change colour compared to 313 this time last year.
And there has been just one report of winter visitor the fieldfare arriving, whereas there were a dozen sightings by the same date in 2011.
The Woodland Trust said the arrival of autumn colour varies from year to year as it is affected by temperature and rainfall, but suggested autumn as a whole was getting later as warmer temperatures mean trees grow for longer.
It is too early to say whether autumn will be later than the average this year, but it already appears to be lagging behind last autumn, which was exceptionally early, Nature's Calendar project manager Dr Kate Lewthwaite said.
She said: "We would definitely expect fruiting to be late because fruiting is intrinsically tied in with flowering, which was late because we had a washout spring which was much cooler than normal, and how were pollinating insects going to get out there.
"All of these things we would expect to have an effect, and we might expect there to be later and less fruit."
Unlike last year's dry conditions, the wet summer this year and recent warm temperatures means the trees are not shedding their leaves so early, she said.
"Tinting is a little bit late, as we would expect."
Experts from the Royal Horticultural Society have predicted that, when it does arrive, the weather conditions over recent months mean it will be a perfect autumn for colour.
Dr Lewthwaite urged people to get out and enjoy woods this autumn, and said they could help experts understand how plants and animals are adapting to the changing environment by recording their sightings on Nature's Calendar.