The science of autumn colour revealed in new book and this video

Huge numbers of people are going down to the woods to soak in the kaleidoscope of autumn leaf colour that is lasting longer than usual in what was known, in Saxon times, as the fall.

The pigment that makes leaves green is beating a slow retreat and the calm, warm weather means the leaves can display their underlying colours for longer before they actually fall, according to a leading tree watcher.

The depth and range of colours this autumn is more pronounced than usual too, because of the cool nights and clear days.

Lemons and coppers, oranges and reds, and dark browns are the most prevalent right now — but pink is also emerging.

Ash trees are turning a lemon yellow, while oak is toning to dark orange or brown.

The sycamores are bright orange and yellow and the beach is a blaze of orange, while the birch is dappled.

“Basically, on deciduous trees, the leaves change their colour in autumn because the tree has ceased to produce green chlorophyll,” said Niall Mac Coitir, the author of Irish Trees.

This is because the weather is too cold and dark in winter for photosynthesis, which produces the chlorophyll as part of its production of nutrients for the tree.

“As the green chlorophyll goes from the leaves, red and yellow pigments emerge that were hidden by the chlorophyll,” said Mr Mac Coitir.

As the tree no longer needs the leaves in autumn, it withdraws the sugars from the leaves into its branches and grows a corky layer of tissue at the base of the leaf that cuts off water and nutrients, causing the leaf to drop off.

The leaf turns from green to yellow, orange, or red, and then eventually falls as its nutrients are cut off by the tree.

The mild weather at this time of year means the leaves aren’t blown off quickly by wind and storms, and so can make the display last longer.

The warm summer has been another factor, with a lot of green, leafy growth produced that in turn leads to a better, more spectacular display as the leaves change.

Meanwhile, in Killarney, “leaf peeping” — a major tourist industry in the fall in the New England region of the US — is starting to emerge, with large numbers of day-trippers and weekend visitors reported over the bank-holiday weekend.

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