20 amazing facts about fall leaves

The word “fall” to describe the season that precedes winter was in use in Elizabethan England, and, logically, relates to falling leaves. Although “fall” is the more common term in North America, “autumn” is preferred in Great Britain.

In Japanese, there are two words meaning “autumn-coloured foliage": koyo and momiji.

While forests in warmer climates may contain a more diverse set of tree species, their trees cannot match ours when it comes to colour—only northern forests are able to pull off this spectacular show.

Tempura-battered maple leaves are a seasonal delicacy in Japan.

You can tell whether or not you have a sick tree, because if it is sick, it will change colour and drop its leaves earlier than other trees of the same species.

Leaf colour tends to depend on tree species: red maples turn scarlet, sugar maples can be orangey red, oaks turn brown, red, or a mixture of the two, and aspens tend to turn golden.

The best fall colours are seen after a series of warm summer days followed by cold (but not freezing) nights.

Dead leaves make great (and affordable) mulch—just make sure you use leaves from healthy trees.

Leaves eventually turn brown because of tannin, the same substance that gives tea its astringency and staining power.

Fallen leaves are an essential part of a forest’s ecosystem, providing protection for tree seeds to germinate over the course of winter.

When a tree's leaves change colour also tends to vary by tree species, with some changing in late summer, and others, like oaks, not changing until many other species have completely dropped their leaves.

If colour is determined by species, how do we get trees with leaves that are green, yellow, and red all at once? That's merely evidence that the process of of chlorophyll disappearing and carotenoids and anthocyanins appearing isn’t always synchronized.

Anthocyanins, which turn leaves red, are also found in blueberries and deep purple fruits like grapes.

Carotenoids, the chemicals that produce orange and yellow foliage, are always present in leaves. However, they’re masked by green chlorophyll until its production is stopped in fall.

Temperature has a slight effect on when leaves change colour, but it's not as significant as decreasing daylight.

Dropping leaves give trees a chance to take a break from the energy-intensive work of photosynthesis.

Leaves change colour as daylight decreases with winter’s approach. Shorter days trigger a mechanism in the tree to close up veins in the leaves, cutting off the supply of chlorophyll.

During the spring and summer, leaves use sunlight to convert water and carbon dioxide into glucose in a process called photosynthesis. Chlorophyll, which gives tree leaves their green colour, is an essential part of this process.

The “needles” that cover evergreen trees like pines are actually needle-shaped leaves.