From snowdrops to frogspawn, the first signs of spring are appearing - but the latest cold snap could put the brakes back on the new season, experts have said.
It has been a "stop-start" spring so far, with wildlife reacting to warmer temperatures last week after the cold snowy spell in late January, the Woodland Trust said.
The recent mild weather saw a surge in reports of snowdrops, elder buds, hazel flowering and even frogspawn submitted to the Trust's Nature's Calendar scheme, which gathers signs of the changing seasons spotted by the public.
The Woodland Trust said it had received 199 snowdrop sightings, 30 of elder budburst, 97 of hazel catkins flowering and 23 sightings of frogspawn so far, as well as anecdotal information from regional staff of wild garlic blossoming in Devon and hawthorn in leaf in Taunton.
But with the latest cold spell sweeping in, the Trust said trees and plants could halt their development and some species fooled by early warm weather such as insects which emerge and cannot return to shelter, could be hit.
Frogs breed only once a year, and if spawn already laid freezes, the breeding effort will be wasted, according to the Trust's Dr Kate Lewthwaite. But really cold weather in April or very mild weather early in January tends to be more damaging for wildlife than the current changeable conditions, she said.
Last year, mild conditions between January and March led to some exceptionally early records of spring flora and fauna and the Woodland Trust is urging the public to send in their sightings to help the charity see how this year compares.
Dr Lewthwaite said: "Milder weather in the past week has accelerated spring after the recent cold spell and Nature's Calendar has seen a surge in recordings of snowdrops, elder buds, hazel flowers and frogspawn.
"However, now the weather is set to turn colder again, we need people to help us gauge what effect this will have on nature."
And she said: "Our native trees, plants and wildlife are great indicators of wider change in the natural world, and we would love more recorders to help prolong the data set we already have."