This is by far the biggest cedar I know in London

Here am I, a Londoner born and bred, a resident for half my life, a committed gardener who fancies he knows something about architecture, a life member of the National Trust – and I had never been to Osterley Park until last Sunday. I had supposed it was just a sad remnant of a great house stranded near Heathrow and bisected by the M4. We arrived to find pure England, left-behind England, unsullied parkland with magnificent trees round a house on a near-ducal scale. Yes, the motorway rules out rural silence, but if you can stomach the aircraft at Kew or Syon they are no worse here.

Osterley is a friendly park open to the neighbours (and there are plenty) all year round. It is a farm with a herd of cows grazing meadows apparently never ploughed, and a real farm shop selling its own produce. And it has a garden becoming a fascinating recreation of 18th century taste. In the borough of Hounslow, twenty minutes from Kensington.

We arrived through an autumn mist that veiled the surroundings. As we walked up the drive, skirting a lake noisy with water birds, the sun pierced the mist, low in the afternoon sky, to outline half a dozen serious cedars of Lebanon, trees that must be contemporary with the massive red-brick house. It was a memorable moment of discovery.

The National Trust can do things so well. You could believe the owners were still in charge – though they left at the end of the Second World War. The 350 acres they gave the Trust is more than the extent of Kew Gardens; enough to feel like real countryside. The Tudor stable block is where you feed and buy your souvenirs, happily free of advertising and bossy notices. The house (with much of its Adam interior intact) shelters you on wet days, and the garden has the unmistakable sense of renewal by imaginative hands. There is a plantsman and a researcher at work here.

You can see it in the ordering of the flower-beds, awkward perhaps to our post-Jekyll eyes, but precisely what Georgian gardeners appreciated; each plant a solo performance. It is clear from the labelling of the beds. The American garden reflects the excitement of newly imported exotics from the American colonies. The walled kitchen garden is a cheerfully productive playground for vegetables and flowers and fruit jumbled together. New tree-planting round the park is original and unexpected – clearly a plantsman’s work. And the mile-long promenade round the great meadow and into the woods must be wonderful in spring with its meadow flowers and bluebells.

The head gardener is Andy Eddy, originally trained at Kew, then at Sissinghurst, and now with a ducal domain of a garden where he can play duke – and duchess. I shall soon be back.

Out of focus, I'm afraid, but my only shot

They came in a goody bag from the RHS at Chelsea in May: five modest corms smaller than walnuts with a name that was new to me: Acidanthera murielae. Late flowering, the packet said. I planted them in a shady bed (there is no choice here) and pretty much forgot about them. In August important-looking irisy leaves popped up. And grew and grew to three feet or so. By mid-September strange flower buds emerged, six or seven to a graceful swan-necked stem, and by the end of the month, six-petalled white stars were opening wide, purple-centred, with a spreading lily-like scent.

Is anything more exciting than meeting a completely strange plant like this: planting it and waiting for a new wonder to appear? The reference books link it to Gladiolus. I can see no resemblance. Acidantheras come, I gather, from Ethiopia, were grown in pots by the Victorians, who called them Abyssinian lilies. They are now firmly in my repertoire.

And when you’ve finished your garden, what then? We tend to dodge this question, saying that a garden is never finished; is a process rather than a place…. there’s always something to do. True if you are a collector, a plantsman, a naturalist or just a passionate observer. Most gardeners, I suppose, start with some sort of plan, or concept, or start to adapt whatever garden they buy or inherit to their idea of what is beautiful or useful. They go on fiddling. It never quite fits their notion, or their notion changes over time. They see something that inspires them or piques their interest, on television, in a magazine or at a flower show. They see a ‘gap’ and make the mistake of filling it: does it call for an urn, or a shrub with strident variegation? In the process, they lose track of their original concept, realise that football takes precedence over potatoes, or netball over roses. They eventually grow stiff with age, give up digging and read up on alpines.

The answer to the question ‘what is your garden for?’ eventually emerges. It is to fill part of your life not covered by work, or satisfied by news – or even by your family. Does it have a spiritual dimension? Poetic or artistic might be a fitter word. What it does do is make you pay attention to the routines of nature – which is surely an excellent purpose in itself

Most of the exhibitors are sheltered by ancestral trees; some shivered by the château

To Chantilly, just northeast of Paris, for the first autumn edition of the Journées des Plantes de Courson. The Château de Courson, southwest of Paris, was the birthplace, 30 years ago, of France’s answer to the Chelsea Flower Show, the key event in the country’s gardening year. Its begetters are a brilliantly creative couple. Patrice and Hélène Fustier, who conceived it as a day for keen gardeners to meet to discuss and exchange plants. In those days, gardening was very much a minority interest in France, with of course fashionably anglophile overtones. I remember, at the Coursons of the ’80s, the startling sight of Range Rovers and green wellies – rare sights around Paris in those days.

The Fustiers invited British judges for competitions (Roy Lancaster has starred at every one.) Specialist nurseries (then rare birds in France) joined in with enthusiasm. Soon the stable yard overflowed into the park and plants of all kinds congregated like party guests among the old oaks; there should have been a Renoir or a Matisse to paint the scene.

This year the Journées des Plantes had a spectacular upgrade. The Château de Chantilly is properly described as ‘princier‘ – princely – rising in faux-Renaissance grandeur among vast lawns and immense moats beside the Newmarket of France, the country’s greatest racecourse and most grandiose stables. The château is also France’s second greatest museum of masterpieces, after the Louvre, thanks to the collectios of the Duc d’Aumale, son of the last king of France.

Chantilly has conference hotels, restaurants and above all the space that Courson could not provide. And the translation, all seem to agree, is a triumph. Patrice and Hélène Fustier continue to preside, with the help of Prince Amyn Aga Khan, and the setting, under and among a grove of ancient oaks and beeches, beside the enormous moat, makes a wonderful frame for the plants.

Sadly the weather last week did not cooperate. A cold spell that saw snow in Belgium and Germany reached an icy finger towards Paris. On the first day it was 7°C and drizzling. Yet somehow the dim misty light made the warm colours of autumn fruit and foliage glow with inner fire.

Relaxed. It’s the one thing that everyone wants to, and thinks they should, be; a zero-sum positive: your face, your clothes, your body-language, your vocabulary, your house, garden and writing-style must be, or aim to be, or appear to be, relaxed.

Every magazine and paper says so, and reports admiringly on anyone who carries it off. Why is it the thing to be? Is it because modern life leaves so little time and space for relaxation?

‘Relaxed’ seems to have the field to itself. What is an admirable, acceptable, fashionable, alternative? No one is admired for being tense, or formal, or uptight. Correct? It sounds as though you’re trying too hard. Of clothes, ‘chic’ perhaps gets away from it, with ‘shabby’ as a possible qualifier.

The sub-text of ‘relaxed’ is that you’re in charge – if only of yourself. You have mastered the situation. You know the rules well enough to ignore them. Rules? Sports have them, but does the rest of life? There are laws and being relaxed about them can get you three points on your licence. But for most of us, white wine before red is as far as etiquette goes. Cheese before pud? We should be relaxed about that; though oddly it is one thing that gets serious society, dining-out society, uptight.

All this is prelude to a gardening question. What is the admiring epithet to use about a gardener whose garden is, shall we say, relaxed? Perhaps in his day ‘Capability’ Brown was considered relaxed. Surely doing away with straight lines, ‘jumping the fence’ and so forth, was relaxing. ‘Damn braces, bless relaxes”, wrote William Blake. Did he never edge his lawns?

Top: A hydrangea at Exbury (I wish I knew its name)

What would I do with them if I took a tenth of the photographs that have tempted me in this last week of five-star weather? I haven’t wasted it indoors. I managed a visit to Exbury on a day as clear as a jewel, the air still and just that crisp side of balmy that makes you (or rather me) feel one glass of champagne to the good. Exbury is always known as a spring garden; the glory of its azaleas and rhododendrons seems to eclipse its other aspects.

Now, with autumn ready to pounce and fires kindling in the maples and liquidambars the occasional rhododendron eccentrically in flower is rather like a black tie at a lunch party. But the harlequin hydrangeas, the pale plumes of the grasses, the colchicums and nerines lead you from glade to glade, and you have time for the infinite variety of the trees; an arboretum framed in monumental oaks.

The New Forest is a gallery of pictures in any season. Glimpses through the trees on the Brockenhurst train make me long to record them. I realised, though, as we raced through Hampshire, the pleasures of the passing landscape, prospects composing and recomposing, crops and copses, swelling downs or dark mantles of woods racing by, are far less visible than they used to be. Railway companies used to clear the saplings from beside the tracks: now long curtains of dull sycamores screen off the scenery.

I spent the weekend of the Garden Literary Festival, the third organised by The Garden Museum, at Hatfield House, the great garden, in the classical sense, that I know and love best. The sky was that ineffable blue; a faint breeze just made the reflection of the great pink house in the lake more liquid, the ancient trees in the Wilderness seemed more massive than ever and the fountains sparkled and crashed in the grand box parterre below the South front.

The delegates at the Festival moved from lecture to lecture, from Banqueting House to Marble Hall, strolling at leisure through parterres on a princely scale like the figures in Repton’s Red Books, almost dwarfed by their surroundings.

The North front has a new adornment: one of Angela Conner’s dramatic water sculptures (and I should guess her biggest yet). It rises maybe twenty feet in the centre of a circular lawn like two great curving, gleaming horns, splashing water slides that would tempt any toddler, framing a golden globe. Of course I photographed it.

Right: The new Angela Conner sculpture at Hatfield House

I wonder how many gardeners think about the style of their gardens. There are certainly a few historical restorations or reproductions or pastiches, but don’t most of us do what pleases us with our patch, without trying to put it in a stylistic box? If we employ a designer we say (or sometimes fail to say) that it’s in his or her style – rather than, say, the style of Jekyll, or Oudolf, or Gardenesque, or even Italian.

I am reading ‘Gardens in the Modern Landscape’ by Christopher Tunnard, an architect and landscape designer of the 1930s and ’40s who created a certain stir with his opinions and his designs for such modernist architects as Serge Chermayeff. He and his contemporaries were unlucky in that their attempt at revolution coincided with the Second World War. There was little business for them. They influenced the look of the Festival of Britain in 1952, but even that officially-sanctioned style found few takers.

You can see shades of it in Battersea Park, where the Festival gardens are being restored. You can even detect it in some of Russell Page’s designs. Its fundamental rigidity, though, its over-strict self-discipline, is foreign to our native gardening instincts. We are eclectic. If there is a plant we fancy, we find a place for it. We put a table and chairs where we want our drinks, and hang the designer.Tunnard’s book follows the history of English gardening since the Landscape Movement of the 18th Century, and doesn’t like most of it. He picks on Joseph Addison for a start. Addison wrote “gardens are works of art, therefore they rise in value according to the degree of their resemblance to nature”. That was certainly the way painting or sculpture was judged in those days – or in fact until Picasso put two fingers up to nature. It is worth reading Tunnard on the resulting confusion, leading to the Victorians and ‘their glorious, gaudy botch’.

2016 is apparently ‘the year of Capability Brown’. We are all to celebrate ‘the creation of the English landscape as we know it’. Landscape, perhaps; garden, no.

HoraceWalpole (I’m reading his letters on my Kindle: endless gossipy fun and backstairs history) said he loved gloom. Or rather the contrast between gloom and brilliance. He decorated his villa at Strawberry Hill accordingly. The entrance hall and stairs are gloomy grey (in the height of today’s fashion), leading up to the excessive bling of his Gallery lined with scarlet cloth and vaulted and decorated with white and gold.

Walpole might have loved the gallerias on the road down to Tuscany; blinding sunlight alternating with inspissated gloom. (A splendid word, no? Sam Johnson used it, and Milton in Paradise Lost, where I always thought it meant occasionally relieved with glimmers of light. But no: it means ‘thickening’).

He, Walpole that is, would presumably have loved the past few weeks. The garden has scarcely dried out; then comes a day of clear blue sky. The paving has remained fashionably dark grey and the plants green, their leaves luxuriating and their flowers not bothering to open. There have been a few indifferent to the weather. Clematis viticella is cheerfully red at the top of the wall, white phlox at the bottom, a hairy zonal pelargonium I don’t like but which still flowers in deep pink anyway. Surprisingly Salvia patens soldiers on, its intense blue extremely effective in the shade. Anemone ‘Honorine Jobert’ is struggling, agapanthus is slow but steady, Solanum jasminoides album outrageous. Luckily our neighbours seem to accept its invasion.

A lovely surprise: Acidanthera (five bulbs in a goody bag from the RHS at Chelsea) has opened eight spectacular white and purple and sweet-smelling stars high among its gladiolus leaves. And wonder of wonders; Meyer’s Lemon, now 30 years in its pot, on the north-facing verandah where no direct sunlight has reached it in three years, has ripened a dozen perfect lemons and is starting to flower again.

Perhaps less surprising, but worth recording: in the shady greenhouse Gardeners Delight, the sweetest of all tomatoes, is delivering a fair crop of its little scarlet fruit.