Autumn colours appear when chlorophyll breaks down and reveals pigments that were hidden all summer.

The longer version

Shorter days and cooler nights tell a deciduous tree to prepare for winter. The plant withdraws nutrients from its leaves and allows chlorophyll to break down, because keeping the pigment working through cold months would cost more than it returns.

What remains are pigments that were in the leaf all along. Carotenoids reflect yellow and orange, and they fade slowly. Reds and purples come from compounds that many species build in autumn rather than in summer. The balance between them gives each tree and each season its particular mix of colour. Weather shapes the display too, since warm sunny days followed by cool nights tend to produce the brightest leaves.

Where this entry sits

Plants and Trees gathers ordinary and surprising details about how green things live, from the tallest forest giants down to the moss on a garden wall. Expect notes on flowers, seeds, roots, leaves, fungi, and the quiet tricks plants use to spread and survive. The full list sits on the Plants and Trees page, where every entry is listed in order.