The plant has to make a specific decision: when to start preparations for the winter. How it feels to itself, that will happen in one day or another. It is, above all, a drop in the amount of light that will affect the Basque Country. Therefore, not all plants change dress at once, even if they are of the same species. It's everyone's decision.

This decision will entail a great deal of change. It will not produce chlorophyll again, that is, matter that makes the plant green, and it will melt what it has on the leaves and collect its ingredients and store them well, thickening the raw fears in the winter. In the leaves appear other pigments and components hidden under the green dress, which show us the new colors of the fall. This color and orange are brought by carotenes and flavonoids. The reds, on the other hand, are the work of anthocyanins. These must be created by the plant, they are not on the leaves, so they are “more expensive”.

The old enigma of scientists is how in Europe trees tend mostly to colors and how in North America and Asia they tend to reds. Apparently, the red trend trees give a touch to the lice looking for sweat: I've created toxic anthocyanins and I'm moving food to the reserves, so for you I have little and dangerous food.

Unlike other times, in Europe, as the mountain ranges are aligned in the East West, in times of glaciations, many plants, as well as their enemies, would die without being able to cross the mountains on their route to the South to escape the cold. Then, when the trees repopulated the continent, there was no enemy or need to redress... Will it be possible?