Since the Middle Ages, it's been known as May blossom. But should its name now be changed to April?

The flowering of the hawthorn bush has, for centuries, been an infallible sign in England that the month of May has arrived. But, this year, in our warm spring, its scented creamy-white flowers are appearing in many places a good three weeks earlier than normal.

It's not a one-off, according to the Woodland Trust, the green charity which is specialising in recording the signs that spring is getting earlier and earlier because of climate change. So many things are happening, the trust says, that April is, in effect, becoming the new May. Swifts, which in the past returned from their winter migration and started to zip through British skies on about 10 May on average, are already here, the trust points out.

Those are only two of many signs of a massive change in the seasons that have been recorded in the past decade-and-a-half. In the past 30 years of steadily rising average temperatures, spring seems to have got about 10 days earlier in many ways - with the unfolding of the leaves of oak trees, for example, and the egg-laying of woodland birds. But this year's early hawthorn is a particularly significant sign.

"One of the most famous vernacular names for the hawthorn is the May-tree and culturally and historically it is seen as signifying the start of summer," said the trust's Dr Kate Lewthwaite. "But thanks to the exceptionally mild start to the year we are experiencing, this summer signal is arriving three weeks earlier than the 11 May average."