The findings lend powerful support to the idea that a warmer climate - possibly due to man-made emissions of carbon dioxide - is having a direct effect on animals and plants in the environment.
Scientists from the University of Munich analysed data collected from a network of more than 70 botanical gardens extending from northern Finland to the southern Balkans to establish the influence of climate on plant growth.
They looked at information gathered during 616 "springtimes" and 178 "autumns", including the dates when the first spring buds opened and the first autumn leaves turned brown in each garden.
Annette Menzel and Peter Fabian, from the university's Faculty of Forest Science, report in the journal Nature that there was a significant increase in the growing season, with spring arriving on average six days earlier and autumn coming nearly five days later over a 30-year period.
Dr Menzel said the European network of International Phenological Gardens, established in the Sixties by two German scientists, used clones of genetically identical plants to eliminate genetic variation as a possible cause of differences. The gardens were established to observe the change from winter to spring as it spreads across Europe from the south-west to the north- east and so were perfect for studying changes over long periods of time, Dr Menzel said.
"The implication of this is that it is a clear signal from the biosphere that we can observe global change. Ten days may not sound much but it represents a significant extension of a growing season of about 150 days," Dr Menzel said.
The scientists excluded other factors that may have influenced the onset of spring, such as the proximity of gardens to an encroaching city.
Dr Menzel said it is not surprising an increase of temperature has a greater effect on spring than on autumn. "Spring is clearly dependent on temperature, whereas autumn is influenced by other factors such as wind and frost," she said.
One benefit of an extended growing season is that it would result in a greater absorption of atmospheric carbon dioxide by plants, the researchers said.