The time of year that Keats called the ‘Season of mists & mellow fruitfulness’, Autumn is a season famous for its harvest time, turning leaves, cooling temperatures & darkening nights. There are two different dates when Autumn could be said to begin. Autumn as defined by the Earth’s orbit around the sun, begins on the the Equinox & Solstice which falls on 22 or 23 September. However, for the purposes of recording climate data, it is important to have set dates that can be compared, so the meteorological Autumn always begins on 1 September.
One of the most stunning signs of Autumn is the turning of the leaves. The shorter days are a sign to trees to begin to prepare for winter. During winter there is not enough light for photosynthesis to occur, so as the days shorten throughout Autumn, the trees begin to close down their food production systems & reduce the amount of chlorophyll in their leaves.