Why Leaves Change Colour in Autumn

Have you ever wondered why certain trees change leaf colour in autumn, and why some leaves are more red or yellow than others? Let's explore this interesting topic.

- By Wendy Moulton

As we know, trees can be divided into two categories: evergreen and deciduous.

Evergreens

Evergreen trees lose and replace their leaves gradually all year round, as each one ages and falls off. Evergreens in the tropics have broader leaves than their cousins in very cold climates, because they don't need to cope with cold. Most of the evergreens in colder areas have long and thin needles rather than leaves, which enables them to tough it out in strong winds, heavy rain and snow. Some needles are infused with a resin that resists cold and rain, and some of these trees are able to move water out of the cells in the needles if a big freeze comes along. This allows the cells to remain undamaged from the freezing conditions, and after a thaw the plant can continue to grow.