Wander With Wild Things

Friday Fun Fact!

It's a favourite time of year for many -- fall, autumn, that magical time when green swaths of forest turn red, orange, yellow, gold, magenta, even purple, as trees prepare for winter. But how and why do all these changes happen?

Leaves have a broad, thin surface and are vulnerable to freezing and subsequent damage, so in order to survive, the tree must ditch the weak links. The tree seals off the end of the branch near the leaf stem and the leaf is dropped like yesterday's paper.

Beginning in mid-June, days begin to shorten and this signals to the trees that it is time to start the Great Preparation for winter dormancy. Many brilliant colours are always there, but hidden by the deep green of the chlorophyll. As chlorophyll production slows and stops, the green fades and the colours emerge in full dazzling array.



Brown colors in oaks and elms come from a waste product called tannin. Orange comes from carotene. The yellows are due to xanthophyll and are seen blazing on birches, tulip poplars, redbud and hickory, who exclusively show this color, never red.

Bright red & purple colors found in sugar maple, dogwood, sweet gum, black gum and sourwood come from anthocyanin pigments, formed from trapped glucose. This pigment is not produced until chlorophyll starts breaking down in late summer. Anthocyanins lower the freezing point of the leaves, allowing them to stay on the tree longer and buying time to maximize the amount of nutrients the tree can pull out before releasing the leaves to the wind.

Every form of life, be it fauna OR flora, has a unique and specialized way of surviving the seasonal changes that life hurls at it. Here in the Eastern US, one of the best places in the world to view the changing colours of autumn, we are lucky enough to be surrounded by trees who choose to do so in a rainbow salute to the dying of summer before settling into a grey sleep, awaiting spring and green rebirth.