Autumn is a glorious time of year to notice how beautiful leaves are as they change colour.

On deciduous shrubs and trees the leaves are on the turn.

As the tree becomes dormant, a compound called abscisic acid triggers a seal to develop at the base of the leaves, before they fall off. This reduces water reaching the leaf and traps the chemicals remaining in the leaves. They gradually break down, changing the colour of each leaf before it drops to the ground. As the process is gradual, individual leaves will be at different stages, so a tree will have leaves of many changing hues as autumn progresses.

Kew Gardens

Dhuilleag, dè an teachdaireachd
a th’ agad dhuinn an-diugh?

’S e gun tàinig foghar oirnn
’s gun deach na craobhan ruadh.

Niall O’Gallagher via Scottish Poetry Library

Images by Rosie Hopkins, Bernie Bell and Noel Donaldson