The reason leaves change colours during autumn
In the autumn the leaves of deciduous trees fall to the ground in huge numbers but before they do, many of the leaves that have been green for months, change colour and display brilliant colours of yellow, orange and red with a range of shades in between.
Thanks to scientific research the reasons for most of the colour changes are now well known.
The colour changes are the result of transformations in leaf pigments.
Leaves are green because the main pigment in the leaves throughout the
When the leaves begin to die in the autumn the chlorophyll fades allowing the orange and yellow shades to become visible.
growing season is chlorophyll.
This chlorophyll is essential as it enables light energy to be converted into sugars and starches, which simply put, enable plants to grow, flower and produce seed.
Throughout most of the year the green chlorophyll masks yellow and orange pigments that are in the leaves but when the leaves begin to die in the autumn the chlorophyll fades allowing the orange and yellow shades to become visible.
Then, as autumn progresses sugars in the leaves become trapped and as this happens, red and purple pigments form.
So as the leaves slowly die yellow, orange, red and purple pigment’s begin to show in the leaves.
The concentrations and display of these colours is greatly affected by temperature, moisture and sunlight.
For example, early frosts can destroy the mechanism for sugars to promote red and purple pigments and so a really colourful autumn display is shortened with yellow and orange being prominent.
On the other hand, a warm sunny autumn with cool but frost-less nights will provide the best conditions for the brightest autumn colours.
Autumn colour is also influenced by the species of deciduous tree.
Maples can display bright red, orange and yellow colours, dogwoods have more purple tones while the ginkgo has a luminous golden yellow display.
It’s obvious then, that many factors contribute to the making of a spectacular autumn display.
Sadly the whole process can be shortened by the weather with strong winds often removing many leaves before the full colour potential is realised.
However, this year could be an exception with good reports of spectacular autumn colours from many localities.