Why do leaves fall from trees in winter?

If you are used to this column, you know that only one of the following three possibilities is correct:

1) Evergreen trees grow where there is a lot of light, even in winter. When there isn’t enough they die, because their leaves can’t fall off.

2) The sap of evergreen trees has nothing to do with that of deciduous trees : can’t freeze! This is why they are called soft woods.

3) The falling leaves is a bit like the moulting of trees. If they did not fall, there would be no new branches in the spring, they could not grow.

An oak pumps a minimum of 200 liters of water per day into the soil.

The correct answer is answer 2.

Yes, if the leaves fall from deciduous trees (this is their name), it is precisely because the cellular mechanism of these trees will stop completely as winter approaches, to avoid freezing.

You have probably heard a thousand times that this and that tree, or such and that other plant, did not return in the spring, because it was freezing in the winter. IS what freezes in a plant is the sap : turning into ice, it expands and explodes the cells of the plant, which dies.

We must bear this in minda tree is an amazing water pump : an adult oak that rises to 15 or 20 meters in parks or on avenues, at least 200 liters of water are pumped into the ground every day. And thousands of liters contained in the trunk!
This water, contained in the sap, rises up the tree at a speed of 6 or 7 meters … per hour. It is this water and sap that will pass into the leaves and, thanks to the sun and photosynthesis, will capture the carbon in the air and, in return, release oxygen.

In conifers, the mechanism is the same, except that the sap is much denser and does not freeze, even if the temperature reaches several tens of degrees below zero. As for the foliage, which sometimes consists of needles or thorns, it is no coincidence that it has nothing to do with the leaves of other trees: it contains very little water, and therefore no risk of freezing. It is also for this reason that maritime pines or umbrella pines thrive in very hot regions: their needles contain very little water, limiting the risk of evaporation!

For the record, know that the surface of the forests continues to increase in France. It has simply more than doubled in 100 years and now occupies nearly a third of French territory, and continues to gain ground. With agricultural land, over 80% of our territory is green.

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