No, it's not your imagination, spring really has arrived. February may be less than two weeks old but signs that the seasonal shift is upon us are everywhere.

Crocuses are blooming across the central belt and snowdrops are out as far north as the tip of Scotland.

Out of more than 500 spring and summer biological events, such as wild birds laying eggs, the emergence of aphids and the flowering of plants, almost three-quarters show evidence of being earlier, according to Scottish Natural Heritage.

Findings from Kew Gardens suggest some of the UK's native flowers are blooming months before they used to.

Daffodils at the centre in Richmond, Surrey, opened in mid-January - a week earlier than last year - while English Hawthorn is expected to flower by the end of February - more than eight weeks before it normally would.

Nigel Taylor, curator of horticulture and public education at Kew, said the blooms are an indication that climate change is having a greater impact. Since 1952, Kew has recorded the dates on which different flowers open. Around 100 plants are monitored with year-on-year changes tracked.

Signs suggest that flowering looks set to surpass the dates recorded in 2007.

Crocuses set a new record, opening 11 days in advance of the last decade's average.

Mr Taylor said: "Blackthorn, prunus spinosa, is in flower and common ash, flaxinus excelsior, is in flower. These are months earlier than the norm and given that they are species that have evolved in the vagaries of the English climate, the more remarkable because one would expect them not to react so easily to milder weather in winter.

"This suggests the changes in our climate are more far-reaching than previously seen."

Asked when spring begins for gardeners, he said: "That's the $64,000 question. Gardeners do not know any more. I've already planted my potatoes, but will I get away with it? I rather think I will. It's hard to predict. I would say spring starts in January."

According to the Met Office the average temperature in January was 5.3C, almost two degrees warmer than the 30-year January average of 3.4C.

Research by Scottish Natural Heritage shows that flowers have bloomed on average 3.2 days earlier every decade for the past century, migrating birds have arrived 2.6 days earlier every decade and plankton has bloomed three days earlier every 10 years since 1900.

Colin Galbraith, director of scientific and advisory services with Scottish Natural Heritage, said: "These results show that species are responding at different rates to the effects of warming temperatures on land, air freshwater and sea, and this could ultimately mean that timings of natural events will become so out of balance as to affect food webs and competition between species."