Why do leaves fall?
When days get shorter, leaves fabricate less growth hormone, called " Auxine ", cells at the base of the petiole (or leafstalk) are weakened and the leaf falls down.

Why do leaves change colour?
In summer, green colour comes from some chlorophyll. In autumn, the chlorophyll is degraded, unmasking other pigments which pre-exist:
· carotene: orange with red.
· the xanthophyll: yellow
· the anthocyanin: red, purple, crimson.
Their colour is bright all the more as light is intense, because they need luminous intensity to manifest themselves. To deepen...

In the opposite, the Copper Beech, leaves of which are not green but purple in summer, turns to the dark green in autumn!

The fall of leaves spreads out over more than one month, over shorter period finally than the appearance of leaves (which spreads out in general from March till May). The date varies from a region to the other one according to degree of latitude and to altitude, and even in a given region, it varies from year to year, little nevertheless, as shows the following example.

We chose some pictures of trees in autumn, as well as leaves represented flat. Trees with resplendent foliage are listed.

Rubric Pictures

Research of pictures on the site
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