A mere half lemon-slice of moon was enough to light the garden last night – or rather to fill its shroud of mist with light. November, moon and stars and mild air is an unusual mixture, the garden seems to hold its breath for winter, with no change more urgent than another leaf spiralling to the ground.

Moonlight views have always fascinated me. They are almost impossible for painters (or so I suppose, or wouldn’t we see them in every gallery?)

They simplify so much that they reveal the very basics of mass and proportion. But they falsify by cutting out the details of colour and texture on which we base most of our gardening judgements.

It’s odd, isn’t it, that only the sort of painters who hang on park railings dare to paint inherently beautiful scenes. There was rising mist on the ploughed land yesterday as I took my usual walk through the low meadow among the bat willows, then up to what I think of as our Downs – the swell of sandy land and short grass. For a moment the dark plough, the verticals of the willows and thin white mist were absurdly picturesque. No real artist would have looked twice. ‘Chocolate box’ describes a subject as much as a technique.

The ground was squelching after weeks of rain when we arrived in Scotland – and the sun was shining. The rain we had been praying for in the South made a four-day visit, leaving the North clear of cloud and lit by a low sun so bright that driving westwards in the afternoon became a challenge.

It is a strange light for gardens, gilding half the scene and casting the rest into deep shadow; not the time to take decisions (or photos). On our way home we called at Howick, the extraordinary arboretum on the coast near Alnwick that puts most other tree collections to shame in the originality and profusion of its planting. Lord Howick seems to have almost commuted to the Far East. His collections of seed-raised trees and shrubs cover acre after acre.

You may have to navigate through long wet grass to read the label on a tree in heavy berry mode or colouring brilliantly, but the bold way a plantsman can take on a whole landscape is inspiring. The valley winding a mile down to the sea was clearly once a beech wood. Immense old trees stand with a faint air of doom among the wind-torn remnants of their contemporaries; a landscape from nature that suggests natural continuity rather than the imposed order of a botanical garden. And yet there are trees here we would consider touchy in the south, and trees we never see, in a bewildering range of families prolifically interwoven. The light was fading, the sun brilliant on the western horizon, the urge to return intense.

It’s a simple question, but not easy to answer: why am I so drawn to old gardens, old houses… anywhere palpably old? What is the appeal of history? What does it matter that (let’s say) a garden has been growing, in more or less recognizable form, for a century, or centuries?

To people who think or feel as I do age gives a sense of validity. I am easily seduced by the word ‘authentic’ – although who is to say that what’s left of the past is more authentic than what has just been created? It’s hard to argue rationally that Dickens’s London is more authentic than, let’s say, Canada Square.

Surely what speaks of today, made and inhabited by living people, is more real than anything remembered – let alone reproduced. Yet I hanker for traces of the past, for scraps of grey brickwork or stone that have, as we say, ‘seen a lot of history’. Somehow they offer reassurance. I see new buildings, or new planting, as something provisional, as though it were waiting for some sort of authentication that comes only with passing time. Patina adds a vital dimension to the actual. It lets imagination get to work, ‘authentic’ or not.

Do you remember Stanley Holloway in the Tower of London? ‘It’s ‘ad a new ‘andle, and per’aps a new ‘ead, but it’s still the original axe’. It’s what you might call an existential question.

Marks Hall (it was raining)

It is not easy to plot the chromatics of autumn. Timing is tricky, but so is the matching of tints that vary from year to year. A tree that turns yellow one year will do orange the next, or a bush usually reliably red go off in a sulk of yellow. There are consistent performers; Acer palmatum Osakazuki is famously hard-wired for a fiery climax, but mainly we just trust that October and November will give us the visual warmth we crave.

Spring is not so different: pricks and splashes of bright colour on bare branches or bare ground are scarcely susceptible to colour coordination. We just have to put up with pink screaming at yellow.

When someone does make a successful effort, though, at more subtle and considered colouring the result can be marvellous. We walk more and more often these days in the rapidly developing arboretum at Marks Hall, twelve miles away near Coggeshall. The Winter Walk beside the lake there is planted with real sensitivity for quiet autumn tints. (We do well in East Anglia for winter gardens: Anglesey Abbey and the Cambridge Botanics both have splendid examples.)

At Marks Hall the groundwork, as it were, is done in tufts of a delicate buff grass, a pennisetum, like big stitches in a tapestry.Through it run skeins of dogwoods and spindles that turn tender shades of pink and buff, grey and rose and yellow. There are gold-leafed ginkgos overhead, white-trunked birches and sage-green sarcococcas. It is the deliberate limitation of the palette, the avoidance of high-pitched colours, that gives it resonance.

We are not spoilt for good woodland gardens in Essex. Beth Chatto’s is an exception, of course. Marks Hall Arboretum is becoming important enough (as I have risked before) to be dubbed our Easternbirt.

The frost (it was only a touch) that browned the face of the Bishop of Llandaff last night was the first here for seven months. Mid-March was our last even moderately cold weather. The cold spell that gave last winter its fearsome name started in late November and reached its climax over the weekend before Christmas, when I recorded two days of bitter cold and clear blue skies, and the greenhouse door froze shut. The lowest temperature on our thermometer, sheltered on a north wall, was -9°C. Since then the coldest night has been January 31st, with a low of -1°C.

Now we are cruising in an autumn so benign that the dahlia is the only plant complaining. My complaint is drought. Ten months have given us only 400 millimetres of rain. We need 200 more in two months to hit our long term average. The wonderful thing about averages is that they always turn out about right.

In spring I complain that everything is happening at once; I panic at the hectic pace of growth and the daily changes in shapes and colours. I fall behind in even seeing, let alone being constructive Now the garden has slowed almost to a standstill is the time to plan ahead, to decide on winter work, to make serious decisions.
But no; lassitude takes over. I am not seeing clearly or analytically; not seeing the garden as a picture, just passively absorbing the atmosphere of the settled, somnolent world.

Beauty in a state of déshabille is a stiff test for a garden. It can be poignant, though, and it can reveal the quality of a good design. We went to her garden to remember the peerless Jill Cowley last Sunday; the garden she made with her architect husband Derek Bracey at Great Waltham. Jill suffered for ten years with a bone cancer that put her through hell. Only in the last two years did it stop her gardening, though, or playing a key role as deputy chairman of the National Gardens Scheme (she was its Essex County Organizer for ten years).

For two years now the grass has been cut and the hedges trimmed; in the borders, though, among the roses (they clamber up every tree) and the unpruned shrubs, it has been the survival of the fittest, The result? A revelation of the gardening style of the 1970s and ’80s, powerfully geometrical, decisively linked to the old farmhouse and dairy and linking them to a garden house, a pergola, statues, a bridge over a (now dry) pond, and memorable views into the surrounding farmland. We have an advantage here in Essex: the fields are lined with shimmering silver willows, now in autumn the precise shade of olive green that seems to be de rigueur in fashionable decorating.

The Gibberd Garden at Harlow belongs to the same school of design. So, to a point, does our own at Saling. The difference in Jill’s is the intelligent exuberance of her planting, still traceable in its déshabille. Jill was a traveller, a reader and writer, a gambler, a person who filled more spiritual space than others – which, perhaps inevitably, made her a great gardener too.

We have been travelling far more than usual in the past couple of months, coming home for a few days only to set off again – to Germany, Italy, Wales, France (twice). And, strange to say, the garden has hardly budged. You can’t keep dashing off like this in the first half of the year, but in autumn the garden settles down to a gentle tick-over. And there has never been an autumn more settled and stately than this.

Day after day in October with a clear sky; high pressure yet mild temperatures.

The michaelmas daisies and chrysanthemums that fill the borders now, the dahlias and salvias and fuchsias and cosmos and cleomes, gradually expand, put on weight, begin to lean and topple, but the picture scarcely alters. The purple vine is heavy with clusters in the branches of the golden acacia. ‘Buff Beauty” has heavier flower-trusses than in June.

An unexpected bonus of last winter’s cold is the late flowering of one of my favourites: Francoa ramosa with its graceful white saxifrageous flower-spikes. After last winter there was hardly anything left of its low furry-leaved clumps. In their slow recovery they missed their summer flowering date altogether. For six weeks now they have been keeping company with the bright blue Salvia ‘Guanajato’; unlooked for, dazzling, lovely.

How much can you recall of the priorities of the past? I read of the recession of the ’80s, or the collapse of the ’70s, with only a dim recollection that there was trouble of some kind. The decades rumble past like goods wagons down the track. I take down the green bound volumes of The Garden that contain the first four decades of this diary (or most of them) without a clear idea of what I’m going to find.

1981, 1991, 2001 …… what was I writing about three, two and one decades ago? I can tell you. At this time of year in 1981 it was the remarkable success of

The Woodland Trust, then almost ten years old. It already had 15,000 members and had just bought Stour Wood, 134 acres in Constable country, for £70,000. I was also celebrating our new-built conservatory, and marvelling at how quickly its new plants were growing.

Ten years later I was preoccupied with our new property in the Auvergne, and with the murky water in the moat at home. Another ten years and the theme was a year of prodigious growth: 2001 went from a wet winter through a mild, frost-free spring (rather like 2011) to a summer weighed down with flowers, fruit and foliage. I measured a young oak that grew 14 inches in a single day.

That’s the joy of gardening: you could change the century, as well as the decade, and we’d be banging on about the same old things.