Why do some trees not drop leaves?

Why don't fir trees lose their needles in winter?

There are colorfully decorated Christmas trees all over the world. Firs are chosen almost everywhere for this - because while the deciduous trees have long since lost their leaves in winter, all conifers are still fresh and green.

The fact that fir trees survive the winter without losses is due to the fact that their needles are structured very differently than the leaves of deciduous trees. Foliage leaves are very thin and have a large surface area that is soft and tender. A needle, on the other hand, is much smaller, but thicker and harder than a leaf. In summer, leaves and needles absorb sunlight.

All leaves are made up of different cells: solid tissue and thin cells. The cells convert sunlight into energy and pass it on to the tree. Foliage leaves have hardly any firm tissue, but can absorb and convert a lot of sunlight. But precisely because they are so soft, the leaves would quickly freeze to death in winter. Therefore, in autumn the tree draws the remaining energy from the leaves as a reserve into the trunk and sheds the leaves. He protects himself from freezing.

The hard, small pine needles, on the other hand, have fewer energy cells and a lot of strengthening tissue. That makes them robust. The needle also has something very special: a kind of sugar that works like a built-in frost protection in the cells.

This prevents the water in the cells from freezing and the needle from freezing. The needles do not have to be discarded because they pose no threat to the tree. And because the fir trees can collect solar energy all year round, it doesn't matter that their needles are much smaller than leaves.