Why deciduous trees shed their leaves in autumn - and conifers not
If deciduous trees were to keep their often large and thin leaves over the winter, they would freeze to death in frost. The sensitive foliage does not have any protection against frost, but has to be supplied with water and nutrients by the tree. Basically, the fall of leaves in autumn serves to protect the tree: if it kept its leaves, it could neither feed nor protect it from the cold and would inevitably be damaged. Instead, it pulls the nutrients out of the leaves - which is why the leaves change color - and then discards them. Conifers, on the other hand, have developed a different strategy: their leaves, the needles, are very small and also surrounded by a protective layer of wax. Therefore, they cannot freeze to death in winter and stay on the tree.
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Which trees do not lose leaves?
Most conifers, with the exception of the European larch, are therefore evergreen. There are also evergreen deciduous trees, which you can recognize by their very small, thick leaves. A typical example is the boxwood. However, there are other variants in which trees keep their leaves in winter.
Evergreen trees
Evergreen trees keep their leaves all year round, simply replacing old leaves. Depending on the tree species, the leaves stay on the tree for between three and ten years. In addition to the conifers, there are few evergreen deciduous trees, but they are not trees. For example, evergreens are:
- Bamboo (Nandina domestica)
- Cherry laurel (Prunus laurocerasus)
- Firethorn (Pyracantha)
- Holly (Ilex)
- Boxwood (Buxus sempervirens)
Semi-evergreen plants
Semi-evergreens are trees that stay green in mild winters and only shed their leaves at very frosty temperatures. This group includes, for example, the Akebia (Akebia quinata, also climbing cucumber) and the oval-leaved privet (Ligustrum ovalifolium). These species are also not trees, but a climbing plant and a hedge plant.
Evergreen trees
Wintergreen plants, on the other hand, keep their leaves (often dried up from autumn and therefore brown) and only throw them out in spring when the new leaves shoot. This group includes some native deciduous trees such as the hornbeam, the oak or the common beech.
Tips
Bamboo can be several meters high and is often used for hedge planting, but botanically it is a grass and not a wood.
