Autumn is one of our favorite times a year. As a company that plants 10 trees for each item purchased, we love all the ways that trees bring beauty to our world.
The changing of leaves every fall adds a splash of color to our cities and forests alike. Leaves can turn yellow, gold, orange, red, and even purple depending on the species. But why does this change happen?
What makes a tree’s leaves green?
The leaves of a tree are what powers a tree’s growth and development. Each leaf produces the food the tree needs to survive. Leaves get their green color from cells containing chlorophyll. Chlorophyll is a chemical that absorbs sunlight and turns carbon dioxide and water into carbohydrates.
What causes the leaves to change?
Some trees have yellow, orange, and red pigments in their leaves. How these pigments shows up depends upon how much chlorophyll is contained in the leaf’s cells. Trees with deep green leaves have enough chlorophyll to mask the underlying pigments.
In the fall, due to changes in temperature and the amount of daylight in a 24 hour period, the leaves stop producing food for the tree. The chlorophyll that gives the leaves their green color begins to break down, which reveals other pigments in the leaves.
Why do the leaves fall from trees?
Not every tree loses its leaves, but most species of broadleaf tree do. Once the leaf no longer produces food, the tree sheds the leaf and prepares to grow new ones. This happens when a special layer of cells begins to develop where the leaf meets the tree’s branch. These cells eventually sever the leaf from the tree.
In some tree species, like oak trees, this process does not occur. Most oaks hold onto their leaves throughout the winter and shed them once new leaves begin growing in. Some broadleafed trees that grow further south are evergreen. Evergreen trees, like pines, do shed old needles, but they do not lose their leaves the way deciduous trees do.
Weather affects color
Have you ever had a tree that turns bright yellow some years and a darker orange others? Leaf colors can sometimes vary from year to year. This is due weather variables, like the amount of light, air temperature, and water.
Colder temperatures just above freezing promotes anthocyanin formation in leaves, which causes them to look redder. Early frosts, however, will reduce the redness of the leaves. Increased rainfall generally increases the vibrancy of all leaf colors.