why do leaves change color in autumn?

1green leaf

All summer, leaves are green because they're packed with chlorophyll, the pigment that grabs sunlight for food.

2needs upkeep

But chlorophyll is fragile — it breaks down constantly, and the tree keeps rebuilding it using sunlight and warmth.

3days shorten

Autumn brings shorter days and colder nights. The tree senses this and starts sealing off each leaf at its stem.

4green fades

Once sealed off, the leaf can't make new chlorophyll. The green fades fast, unmasking colors that were there all along.

5carotenoids

Yellow and orange come from carotenoids, pigments that were in the leaf the whole time, just hidden under the green.

6anthocyanin

Red comes differently — some trees make fresh anthocyanin pigment in autumn, often when sunny days follow cold nights.