see if I could detect any warmth. I could, but only just. That alone should be enough to tell the natural world to hurry along, to wrap up and get ready for what is to come.
Yet it is the intensity of the light that dictates the radiance of the autumn leaf colour. Leaves absorb red and blue wavelengths from sunlight, reflecting the green light to us. Green is good. Green tells us the tree is alive and well. If something goes wrong, such as a drought, the leaves begin to yellow because the green chlorophyll is no longer being fed, causing it to break down. It can’t absorb the red light any longer, so it gets reflected outward to our eyes. It is this mixture of red and green light that creates the yellow. The loss of green is a biochemical phenomenon with high, show-stopping drama and profoundly poetic consequences.
Autumn colour is the universal manifestation of the same process. Dictated by plant hormones, as the length of daylight recedes, the water and minerals, especially phosphate, that have fuelled photosynthesis all summer long, are cut off in deciduous plants at the stem of the leaf. The powerful green pigment in chloroplasts, chlorophyll – which, as every biology pupil knows, is the essential component for converting sunlight into sugars and is responsible for what John Cowper Powys described as ‘an enormous green tidal wave, composed of a substance more translucent than water, has flowed over the whole earth’ and what I call the ‘great green stain of summer’ – begins to fade because it can no longer replace itself.
Without the supply of water and phosphate, chlorophyll burns itself up and disappears, allowing other pigments that are always there but drowned by the green wave, to begin to show through. These are principally carotenoids, bright yellows and oranges, and anthocyanins, the reds and purples, hence the drama and the rush for the poet’s pen. But their celebrity is brief: they, too, are doomed to the same fate as the chlorophyll, which is why this whole process is uncharitably dubbed ‘autumnal senescence’.
As the nights grow steadily cooler, the anthocyanins are responsible for removing sugars from the leaves the tree is about to shed. Only when the leaf is of no further use to the tree do the leafstalks grow cork cells to close off the conductive veins with plugs of special water-absorbent tissue. These freeze with the first frosts and the cells burst open, causing the leaves or needles to fall.
Bucking the trend, our oaks and beeches lose their chlorophyll like the rest, but stubbornly refuse to drop their leaves, an esoteric adaptation known to botanical boffins as ‘marcescence’. No one knows quite why this is, but there are several plausible theories. Some say the dead leaves hide the new buds and deter damage by herbivores, such as deer, evidenced by the measurable observation that the lower, younger branches, those within browsing reach, hold their leaves longest.
Others proffer subtler and rather more imaginative hypotheses that retained dead leaves collect snow, which acts as an insulating blanket to protect developing shoots in the depths of winter and also hold it longer in the spring thaw, thereby providing a water supply to their roots at a time when the ground may dry out too rapidly for the tree’s comfort. I find that idea challenging. Yet others have proposed that the dead leaves contain sugars that will better benefit the mother plant if released in the spring when the nutrients are most needed. The theory I consider the least likely is that oaks and beeches (hornbeams too) are slightly backward from an evolutionary perspective – less biologically intelligent (the very suggestion!) – and haven’t yet fully worked out how to shed their leaves quickly. Whichever is the case, or maybe none, I draw comfort from the notion that nature reveals its motivations only slowly; mysteries within mysteries that keep us arrogant, would-be know-alls firmly in our place.
* * *
There is so much going on in October that there should be a better, more uplifting name for the passage of autumn into winter. The Mellowing, or the Misting perhaps, or the more intimate double-entendre, the Rustling. That’s what I hear when I close my eyes and stand underneath the rookery at the end of the month. For the moment the rooks had upped and gone, leaving only a vapid sky and an unavailing silence behind them. I wouldn’t expect them back permanently until February, but if they happened to be passing in their unruly troops, they’d occasionally drop in for a few hours and clog the trees with their quarrelsome bustling, like school-kids claiming their spaces well before the bell goes. But in today’s soft rain they were absent, and the oaks and sycamores solemnly dripped in an uncluttered, graveyard silence. When I stood completely still, a transcendental moment with only the pluming of my breath to reveal my presence, the silence bent to a lower urgency than a rowdy rook could comprehend. Beneath my feet, all around me, busy, industrious life was at work.
I have often noticed that life beneath the rookery is fuller, richer and more diverse than similar habitats nearby. Logically, when you consider the rainfall of nitrogen-rich droppings from on high during at least five months of each year for well over a hundred years, coupled with the annually layered carbohydrate of mouldering leaves from the sycamores and oaks, it is hardly surprising that the soil is rich. Here, beneath the trees, despite the shade, the naturalising daffodils I have planted are always finer, taller, grander and a richer gold than elsewhere.
Off to my left, with quick, jerking thrusts, a blackbird was cashing in, flicking rusty leaves, as if turning the pages of an ancient tome in a rushed search for wisdom. A restless robin fluttered from the wooden fence to the ground and back again, always pert, chinking its little metallic assertions, always checking out where my footsteps might have delivered up a worm, a bug or a centipede. And somewhere invisible, somewhere under the wind-blown waves of leaf litter, a shrew was blindly burrowing in its own private, nose-quivering, bristle-trembling quest.
Everything alive knows that winter is coming. Everything needs to hurry, to feed, to lay down fat, to burrow down, to bore deep into the sanctuary of timber or soil, to crawl under stones, into hollow logs or mud, to build nests, to take in bedding, to batten down. Need and haste: those are the two bywords for this moment in the year. They are the apothegm by which so much survival hangs. The bell for last orders has sounded loud and clear. Even the moon seems to know it, as it rounds to its chilly apogee, trailing mercurial pallor across the lawn and freezing the shaggy world with an icing that crackles like fire beneath my morning feet. By the time the stifling snows and vicious frosts arrive, for many it will be too late. Nature takes no prisoners; it renders no quarter to the unprepared.
The red squirrels were busy building a new drey. I was watching one yesterday, scurrying (its Latin name is Sciurus). It was pruning fresh larch and pine fronds and bearing them along in its teeth, fronds sometimes fully its own length, then weaving them together with the practised eye of a gypsy wife making baskets, pushing, bending, pulling, intent, labouring away with paws and teeth, totally oblivious to, or more likely just ignoring, my silent presence a few yards from the foot of the tree. Time-served though they may be, my field skills cannot boast the fooling of a squirrel on high. It knew I was there, all right, but I was no threat to that tail-flicking, nose-twitching, bright-eyed red, busy about its urgent affairs. Only one thing burdened its mind: winter.
Earlier in the day I had watched two of these enchanting native squirrels at the nut box I had put out for them. (We have no pox-carrying greys in the northern Highlands yet – they haven’t crossed Loch Ness – and I pray that we may have the resolve to keep them out.) They were busy feeding, laying down fat, but also carrying off the hazelnuts in their teeth and burying them with rapid, jerky forepaws, scrubbling out the shallow cache pit, carefully dropping the nut and filling it in again, even scattering a few leaves over the top, all in a matter of a few seconds. Then back to the box for more. What makes me chuckle at this important caching of winter supplies is the ritual furtiveness of the process: the casting-around to see who else might be watching, with the shifty look of a shop-lifter about to pocket something, the nipping off to a quiet corner, the frantic digging, then more furtive glances while sitting upright on its tail for a better view, and scuttling back for another nut.
And the question I am so often asked: can they remember where they have buried the food? The evidence seems to be that
