Bluebells are flowering much earlier than in last year's cold spring, with peak displays expected in time for Easter, the Woodland Trust said.
The charity said nearly 200 records of native bluebells had been submitted to the Nature's Calendar website, which asks the public to submit sightings of natural events which mark the changing seasons.
This time last year, just 43 records had been submitted, as the UK struggled to shake off cold weather.
The trust is expecting a much earlier average first flowering date for bluebells than in 2013, when the average date across the UK was May 5. The earliest average first flowering date on record was April 4, in 2012.
Long term records show that the flowering dates for English bluebells have got five days earlier in the last 50 years, the Woodland Trust said.
Other spring species are flowering up to 12 days earlier over the last 25 years, as a result of climate change, according to the charity.
The Woodland Trust is calling for better protection of ancient woodland, one of the native bluebell's key habitats, to give the plant the best chance of survival in the face of increasing threats from climate change, development and invasive species.
Woodland Trust director of conservation Austin Brady said: "Climate change is not only affecting flowering dates but is also a factor in the number of pests and diseases in the UK quadrupling since the year 2000.
"Combined with Government's clear misapprehension that ancient woodland is protected from development, the Woodland Trust is deeply concerned about the future of English bluebells and many other native species.
"Increased protection for all ancient woodland is vital, and linking them with newly planted woodland and hedges will allow wildlife safer passage through the countryside.
"This will help to make our countryside more resilient, and offer more scope for adaptation to the impact of climate change too."
:: To record bluebell sightings, members of the public can go to woodlandtrust.org.uk.