The turning of the foliage is something we are very familiar with, at least those of us who live in parts of the world that experiences the four seasons. We accept and relish in the colours of golden, reds, purples and browns that turn the landscape into warm paintings created as if by brush strokes of a skillful artist.
But only few of us ever consider the reason and the means by which this natural phenomenon take place. So, why do leaves change colour?
Interestingly enough, the complete details of this process are not yet understood, but scientist do know enough to be able to explain the basics.
Leaves are the food factory of the tree. Water is transported from the ground through their roots and together with carbon dioxide from the air and sunlight, plants can produce glucose, a kind of sugar. This process is called photosynthesis. Glucose is what we might consider being the food for plants, which makes them thrive and grow.
Leaves do naturally contain several colours, even reds and browns, but the dominating colour during the spring and summer is green, which comes from the pigment called chlorophyll, an important chemical vital for the process of photosynthesis.
When summer comes to its ends and autumn arrives, the days become shorter and the absence of light is obvious - this onset of darkness is the signal that prompts the trees to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis and it shuts slowly down, commencing in the fall. The green chlorophyll disappears from the leaves and as it fades away, we begin to see the yellow, red and orange colors. The intensity, the onset and the duration of this turn depends very much on the weather, the climate and the latitude. Sunny, warm days and cold nights produce the most stunning colour displays. The color variation also depends on the bushes and trees and the variety and amounts of the pigment stored in their foliage.
As autumn progresses and reaches its end, the veins that carry fluids into and out of the leaf gradually close off, producing chemicals that will seal the leaf off from the tree branch. This is on order to prevent the leaf to freeze and damage the trees. Once this separation is complete, the leaf is ready to fall.
The tree then enters a state of winter dormancy, not shutting down completely, but resting. Some metabolic and developmental processes do take place in it's buds and twigs, while it prepares for spring and the onset of yet another yearly growth cycle.