Try these garden hacks to help hedgehogs hibernate Hue beauty Why

BREATHTAKING autumn colours help to compensate for the passing of summer. I love watching how leaves change over the year: they start with bright, fresh promise in spring, then they mature, fade and leave the stage in dramatic style. But why do fading deciduous leaves produce such a dazzling display?

Even if the September gales have put paid to so many leaves, their spell hasn’t yet been broken. From my window, I’m captivated by a fine old elm at the bottom of the garden.

A yellow pencil line surrounds some faded leaves; in others, the yellow has suffused all but the very centre; yet more leaves are purest yellow.

While deciduous trees are preparing for dormancy and photosynthesis is slowing down, they no longer need the pigment chlorophyll.

Chlorophyll plays a key role in photosynthesis and its green colour masks those of other pigments in a leaf so, once its dominance fades, the other pigments become visible.

As a general rule of thumb, a predominance of the pigment carotene produces yellow leaves, as we can see with witch hazel, Hamamelis vernalis.

The fiery reds in Viburnum carlesii have a high proportion of anthocyanins, and the orange in Acer palmatum Cascade occurs when the two pigments are roughly balanced.

Have a closer look at your shrubs and you’ll see how all their subtle shades are evolving. During a break while writing this, I caught anthocyanins at work on my Syringa meyeri. The exposed outer leaves were already much redder than the others. The overall impact is a feast to the eyes.

Plants produce anthocyanins that create antioxidants to reduce the risk of cells being damaged by strong sunlight.

But why should trees waste any energy protecting leaves against ultra-violet light when photosynthesis has stopped?

Why not just let them drop? This is a complex problem which scientists haven’t cracked yet, but research outlined by David Lee in his book Nature’s Palate in 2007 gives us a pointer.

In 2003, a major study found that the red leaves in trees that produced large amounts of anthocyanins contained less nitrogen than those with yellow leaves.

Scientists believe that these trees are able to re-absorb nitrogen which they then store in the trunk. They would find this invaluable the following spring.

When I look at the ancient alder woodland bordering our smallholding, I wonder if these nitrogen-fixing trees look so dull and drab in the autumn because they’ve got plenty of nitrogen