Autumn colour

The change of season is upon us – have you noticed? Extra blanket at night, shorter days, fungi popping up, and many trees changing colour – the deciduous ones anyway.

We can thank early settlers and the Victorian Acclimatization Society for some of the beautiful autumn colour we experience at this time of year. In 1857 and 1858, Victoria’s first Government Botanist, Ferdinand von Mueller, is said to have distributed over 7,000 plants and more than 20,000 seeds to various gardens and parks throughout the new colony. Mind you, some introductions turned out to be a bit disastrous, like rabbits, and von Mueller championed the introduced blackberry as a source of food for the bush and for erosion control!

Trees from northern climates such as the oaks, planes, maples and birches in our streets and parks, have evolved to endure long, cold winters. The shorter hours of daylight is the main trigger for the introduced trees to enter a state of dormancy by dropping their leaves.

Less sunlight means less energy to drive the process of photosynthesis. Photosynthesis takes place within the tree’s leaves and is the means by which the trees obtain their nutrient. The photosynthesis equation looks like this: carbon dioxide + water (with sunlight and chlorophyl) = glucose (food) + oxygen.

As the hours of daylight shrink, the trees begin to break down the chlorophyl in the leaves and store it for the winter. The leaves lose their green pigment and other chemicals within them begin to provide the reds, yellows and purples of autumn that begin to dominant: carotenoids produce yellow and orange shades; anthocyanins produce reds and purples.

Well, who really cares about all that? It’s just a nice time of year to celebrate the wonderful change of season that Mother Nature provides. We will soon be looking forward to the joys that spring brings. In the meantime, stay warm.