Autumn is a glorious time of year.  Grass has recovered from the heat of summer and looks green rather than straw, whilst trees and shrubs exhibit vibrant colours of red, orange and brown.  Of course, it can also be a time of storms with heavy rain and gales as the daylight dwindles and nights turn colder.

The colours of autumn vary with the weather.  The green of plants is due to the chlorophyll, the wonderful substance that can absorb sunlight and carbon dioxide to produce sugars and emit oxygen.  At this time of year, deciduous plants are beginning to close down for winter, brought on by falling temperatures and shorter daylength.  Lower temperatures destroy chlorophyll but the leaves contain other pigments including yellow xanthophyll, orange carotene and red anthocyanin, which come to the fore as the chlorophyll declines.  On warm days as the sugars become more concentrated more anthocyanin is produced enhancing the red colour.  Hard frosts however, destroy the other pigments too and the leaves soon fall off.  The best autumn colours can be seen in a period of warm sunny days and cold, but not frosty nights.