With snow-crested needles and a vibrant green hue, evergreen trees stand out against the otherwise drab landscape during the cold winter months. While other trees have long since lost their leaves, evergreen trees stand out in a forest as they stay full throughout the whole year. The science behind why evergreens keep their leaves, however, is more complicated than some think.

Most trees lose their leaves in the winter due to the lack of sunlight. As the days get shorter, there is less sunlight to photosynthesize. This means the chemical in leaves that photosynthesizes, chlorophyll, isn’t needed anymore, so the trees stop supporting their leaves and essentially go dormant. Chlorophyll is the reason behind green trees. Without it, the leaves turn orange, then brown before they eventually fall off.

Yet unlike other species of trees, evergreen trees keep their leaves despite not being able to perform photosynthesis, even though they maintain their chlorophyll. This is because, while evergreen trees maintain the chemical needed to photosynthesis, the cells are dormant, meaning they can’t. Maintaining their leaves allows them to grow more durable needles for longer periods of time, as they don’t have to regrow each season. Because of the structure of the evergreen needles, it takes less energy to maintain the metabolism needed to support them all winter than it takes to regrow them every spring.

One problem faced by a lot of evergreen trees is preventing cellular freezing in sub-zero temperatures. Evergreen trees achieve this by creating their own kind of natural antifreeze in their cells. This is done by accumulating chemicals called cryoprotectants. When dissolved in water, these substances lower the freezing point of water, making it much more difficult for an evergreen tree’s leaves to freeze.

Another problem faced by evergreen trees is the risk of broken branches from the sheer weight of the snow. This is what has in part led to the iconic needle shape of evergreen trees’ ‘leaves’. This shape allows snow to fall through the branches rather than taking them down and risking structural damage to the tree.

Evergreens are benefited by maintaining their leaves as it takes less time for them to spring into action after winter than deciduous trees. They do not have to regrow any leaves lost, they essentially just have to ‘wake up’. Because of this, evergreen trees are much more durable in more northern mountainous regions as they can take full advantage of any sunny day they have.