The Woodland Trust's Nature's Calendar has already recorded the appearance of that early signal of summer - the hawthorn, writes PETER CANN

April is the new May, as this year's bizarre weather continues to bring sightings of species normally flowering in May like hawthorn and the oxeye daisy - both ahead of their traditional flowering dates - and swallows and swifts returning ahead of schedule.

As the Woodland Trust's Nature's Calendar records show, despite the apparent cold start to the year, the monthly temperatures have actually been slightly above the average.

The maytree, mayblossom, mayflower, maythorn, maybush are all common vernacular names for the hawthorn, one of the best loved native British plants.

Research by the Woodland Trust going back decades points to changes in the plant's timings over the past 30 years, suggesting these days it could be more appropriate to call it an apriltree' or aprilblossom.

Folklore says hawthorn is always late, rarely ever in flower by the first week of May, and such was the wait that villagers would linger on stories of early flowering bushes in order to rush for the first blossom of the year. Workers would also pick the leaves on their way to work to supplement their sandwiches, referring to it as bread and cheese.

But Nature's Calendar shows earlier sightings being recorded.

Dr Kate Lewthwaite, manager of the Woodland Trust's Nature's Calendar project, said: "Climate change is affecting the timing of our plants and wildlife and, over the past 30 years, we have witnessed a marked advancement of spring flowering species in line with annual temperatures.

"An excellent example of this is hawthorn, which holds the clue to its historic flowering time in its many vernacular names. Commonly not seen until early May, over the past 30 years it has been edging its way into April.

"Culturally and historically it is seen as signifying the start of summer, but thanks to the exceptionally mild start to the year we are experiencing, this summer signal is arriving weeks earlier than the May 11 average."

Another common signal of incoming summer is the return of migrating birds such as swifts and swallows, and it seems that even the mixed up weather hasn't affected them either.

Hawthorn is surrounded by folklore and research is being carried out on its possible health benefits, including lowering blood pressure for heart diseases and as a sedative. The blossom of hawthorn is also made into tea which is claimed to help the heart, circulation and cholesterol.

It is very common in hedges, scrub and woodland but is the most commonly mistaken species.

The deciduous thorny shrub has a grey, fissured bark on a knotted, twisted trunk. Toothed leaves appear before a mass of wonderful scented blossom, unlike blackthorn which, when in flower, has no leaves Its first leaves are from March to April and flowers from May to June - April 9 this year. The deeply lobed leaves turn orange and dark-red in autumn.

Fruits ripen to red berries, which are called 'haws', from October to November. The leaves drop in November.

You can help scientists monitor the effect of climate change on this species by telling us the dates when its buds burst, fruits ripen and leaves appear, tint and fall off where you live.

Nature's Calendar is produced by the UK Phenology Network, the result of a partnership between the Woodland Trust and the Centre for Ecology and Hydrology, which has its headquarters in Wallingford. The network now has more than 50,000 registered recorders observing the signs of the changing seasons across the UK.

Phenology is the study of the timing of natural seasonal events, especially in relation to climate. The timing of natural events is sometimes known as Nature's calendar.

For more information on Nature's Calendar, visit the www.naturescalendar.org.uk website.