Leaves are important to plants because they provide nourishment or food for the plants. The food-making process is known as photosynthesis. In addition, young leaves keep the tips of growing stems moist by wrapping around them and protecting them from the elements.
Leaves also regulate moisture and gas exchange within a plant. They also serve as a cooling system, as they release vapor through their stomata.
Leaves begin in buds, form along the sides of the stem and become visible when they start to unfold. Most soft-stem plants form new leaves until the plants produce flowers or a cold weather season begins. Many woody plants shed old leaves and produce new ones throughout the year. Deciduous plants in temperate regions shed their leaves each fall and produce new ones each spring.