The science of recording how plants, birds, and animals respond to changes in the weather was invented in the 18th century. It went out of fashion in the 1940s when the Royal Metereological Society stopped collecting nature reports from its network of amateur recorders. And for fifty years there was no official data.
However, during that time, a largely female army of nature lovers kept the science alive by making detailed records of the plant activity in their gardens. These statistics - originally made for personal interest - are now being used by The Woodland Trust to analyse the impact of climate change.
Anna Egan went to South London to meet Sheila Northover, a newcomer to the now revived phenology network. But first Jill Attenborough of the Woodland Trust took her to meet Mary Manning who has charted the changes in her Norfolk garden for over forty years.
The BBC is not responsible for the content of external websites.