In this beautiful capture by Kim Schou, we see a leafless tree in Vesterborg, Denmark, withstanding the cold of winter in Scandinavia. Like animals that hibernate, trees go through a similar process called dormancy.

During dormancy, things like metabolism, energy consumption and growth all slow down. Losing their leaves lowers energy requirements and is achieved through a chemical called ABA (Abscisic acid). The trees produce this acid in the terminal buds (the tip of the stem that connects to the leaf) and as it gathers it signals to the leaf to ‘break off’. ABA is also responsible for preventing cells from dividing, thus suspending growth until the dormancy period ends. [Source]