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Bright days & cool nights

No, this isn't a weather predication!  Bright, dry days and cool nights are what is needed for truly fabulous autumn colour. Obviously you need to start off with plants that have good autumn colour and Ness has these in abundance. After that the intensity of autumn colour is determined by the weather.

The short days of autumn signal deciduous trees and shrubs to stop growing and prepare for winter. The most prominent sign of this is the changing of leaf colour as the green pigment chlorophyll begins to break down revealing the other pigments that are present in leaves.  Pigments called anthocyanins cause the development of yellow, bronze and red tones.  Anthocyanins, increase in autumn, because the leaves contain more sugars than normal. 

Plants use the green pigment chlorophyll for photosynthesis (the process by which all plants generate their own energy, sugars, from sunlight, carbon dioxide and water).  This process continues as the chlorophyll breaks down but lower temperatures reduce the movement of sugars out of the leaves in to the rest of the plant. 

This results in an excess of sugars in the leaves which are in turn converted to anthocyanins. High light levels increase photosynthesis so there are more sugars in leaves. Lots of rain, however, causes plants to use these sugars to make proteins (basic building blocks of tissues) rather then anthocyanins. So, for really outstanding autumn displays you need bright, dry days and cool nights.

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Back to the Gardens in October