WHY DO LEAVES TURN COLOUR IN THE FALL?

Did you ever wonder what caused a leaf to change colour in the fall? Most people believe that frost causes leaves to die and loose their natural green colour. You may find some of the following information of interest. We do know some of the science associated with this phenomenon, of leaves changing their colours each fall, but Mother Nature has not yet released all of the facts.

The shorter and cooler days of late summer and early fall induce hardwood trees towards a dormant or resting stage of their annual growing cycle. The early dormancy stages trigger a colour change and drying of the leaves, leading eventually to leaf drop. Most hardwood trees use a series of pigments to develop the colour of the leaves. The strongest pigment is green produced from chlorophyll a product of photosynthesis. This process helps the tree to feed its growth cycle through the production of starch. A healthy vibrant tree will showcase a strong green colour throughout the growing season. As the growing season comes to a close the tree no longer requires large amounts of chlorophyll. Therefore the green colours starts to fade and the true colours of the leaves begin to appear. That’s right the true colours of hardwood leaves are red, brown, and yellow. If the fall colours are dull and flat, this is an indication that the trees are under stress. This stress could be caused by drought, acid rain, insect damage, disease or even over tapping. If the fall colours have an abundance of vibrant reds, this is an indication of healthy trees starting the production of sugars from their starch reserves.

Weather is critical to a vibrant long lasting fall colour change. Best colour occurs when fall days are cool and sunny with occasional light frosts.

From: Ontario Maple Mainline Magazine Winter 2006

By: Keith Brown OMSPA Director

Algoma and 2^nd Vice-President

OMSPA