We visit the agreeable old village of Cotignac most years at the end of summer. It lies among the steep pine-covered hills of the Var in the region justifiably known as La Provence Verte. The green is a blend of light and dark; the pure pale green of the Aleppo pine the dominant shade (what tragic thoughts the name of this lovely tree bring to mind today). The dark notes are mainly oaks of half a dozen species, with here and there the exclamation marks of slender cypresses.

Last year I was delighted to discover, the day before departing, an exhibition of the photographs of a colleague of long ago when my career was in fashion magazines. Frank Horvat was an international star at the time when David Bailey and Brian Duffy and their East End friends were making Twiggy and that girlish group famous. Frank took sexier fashion photos than any of them. He remained detached, though, a little aloof, and never became the same sort of “sleb”.

A few years later he made his dissident views plain by publishing a beautiful, even moving, book of portraits of trees. His trees, or most of them, stood alone in fields, on bare plains or mountainsides, sometimes distorted by the prevailing wind, usually just a clear statement of their heredity, their race, fully developed and ready to be admired.

This year I tracked Frank down to his cottage high in the hills above Cotignac, at the very end of a winding dirt road on the lip of a frightening ravine. The stone building, in its clearing among ancient olives, commands an immense view: nothing but forest in rippling ridges, 180 degrees wide and perhaps forty miles deep, to the irregular blue line of the Massif des Maures that overlooks the sea between Toulon and St Tropez.

In his eighties Frank has discovered the internet and realised that it offers his life’s work the chance of a revival. His work could never readily be classified. He puts it, in a book to be published next month, in fifteen categories or ‘keys’, but none of them truly categorical in anything but pictorial terms. Google his name to see his pictures.

I found the meeting, the rediscovery of an old friend and his survey of his own achievement a moving and thought-provoking experience. He has written his observations of the world in light (the literal meaning of photography) over a span of some seventy years. He has ranged from salons to slums, recorded chaos and captured calm. No philosophy emerges from his pictures; he is as free from judgement as Candide, and as free of conclusions – unless you call Candide’s last word a conclusion: “Il faut cultiver son jardin”.

Autumn never announced its arrival more clearly than by today’s damp chill after two days of almost unprecedented late summer sun. We have had our little garden sprinklers on every night for weeks; without them I’m sure there would have been no growth in the garden at all. The climbers thick on the walls (and the roses thrusting six feet above them) suck all the water from the ground. I don’t grudge it, but I must replace it.

Meanwhile preparations are afoot for our new greenhouse. They

started in May when we cleared the biggest bed in the garden (be under no delusion; it’s tiny), digging out, skimming that bilious yellow-leaved spirea, a red-leaved maple, a clapped-out pittosporum and a tall hibiscus. The hibiscus is doing well on intensive care in another spot. A neighbour accepted the maple; the rest went on a skip. We had to remove 80 bags of soil (through the house, of course) to lower the ground level for the future greenhouse. The plot has been filled with potatoes, runner beans, courgettes and salads for the summer. Now comes the prospect of building the base for the house, due to arrive in November.

It is a little gem of an aluminium greenhouse from Alitex; three-quarters of a span, the third quarter resting on the western garden wall. With its finials and its little spiky ridge it will look (we hope) as Victorian as if it came with the house, but need minimum upkeep. There are quite a few plants in pots waiting impatiently for its arrival before winter sets in.

It’s forty years now that I have known the Banks family’s garden on the Welsh border – almost a quarter of the garden’s long life. Four generations of Bankses have been passionate plantsmen and distinguished dendrologists. William Harland B, who bought Hergest Croft in 1912, was inspired by William Robinson and an eager customer of Veitch’s Exeter Nursery when EH Wilson was among those scouring China on their behalf. Many of his introductions thrive here still.

Just how and why the 40 inches of rain, neutral loamy soil and the altitude of 700-odd feet allow or provoke the mighty growth that gives Hergest Croft so many champion or near-champion trees is unclear. I am inclined to give as much of the credit to their proprietors. The biggest plants tend to belong, naturally enough, to those who planted them first.

I was at school with Lawrence, the third Banks to own the garden, and sat at the feet of his father Dick – a wonderfully benign authority. It is easy to see why plants should want to reward such dedicated and expert overseers. Lawrence was Treasurer of the RHS for many years and his wife Elizabeth its first woman (and first horticulturally professional) President until earlier this year.

Today the garden and its adjacent Park Wood are best known for their National Collections of maples and birches. It is easy to be distracted, though, by the awesome firs and pines, oaks, limes and walnuts, ashes, larches, cedars and far rarer things that tower in the arboretum and shade the sheep in the park-like farmland around.

Elizabeth Banks Associates is one of the foremost landscape practices in the country. Is it despite or because of this that there is no sniff of modern or fashionable design to be seen? The Hergest garden remains largely as it was conceived a century ago, its structural elements disguised, of course, by the growth of what were once almost incidental trees and shrubs. Now they spread their branches over path and terrace and hedge. How many gardens, though, keep the deliberate unadorned geometry of orchard and vegetables, soft fruit and perennial borders, greenhouses, rose garden and tennis court, almost in the manner of a farm, where function needs no justification?

How calming it is; how unaffected and truthful. Do you detect a partiality here? Can you tell that I find Hergest Croft one of the holy places of horticulture? I don’t deny it.

However much I look forward to a visit to our Welsh woods I am still amazed by the way they lift my spirits. What can I compare it to? A moment in music when you can’t contain your urge to sing. Finding a fresh breeze on the beam that fills your sails and starts the water running noisily past. A first sip of champagne, indeed.

Entering the woods, feeling the powerful presence of the trees, breathing their unameable smell, tracing in the seeming chaos of leaves the unalterable patterns of each tree’s growth, the cool of their shade, the brilliance of their green, I am lifted onto another level of living and forget everything else. I become a forest creature.

Each time I visit a plot we have planted in the past fifteen years or so I am shocked by the extent of new growth. We were here in June, when new shoots were just sketches of the picture to come. Three months later two dimensions have become three, every tree has added maybe five per cent to its height, but ten per cent to its volume. The same space is even more overflowing with life.

A forest without paths is like a room without doors. Opening tracks and keeping them open is a forester’s first concern. Brambles, bracken, gorse and birch saplings block your way it seems almost overnight. One of the great joys is carving a clearing to let yourself in. It’s wonderful what a neighbour’s big tractor will do.

And an excursion from this demi-paradise? To a true fantasty just up the road, the ‘Italian’ seaside village of Portmeirion, a celtic Portofino with an impish sense of humour. Clough Williams-Ellis turned his romantic imaginings into reality here in this heavenly setting in the fifty years betwee the 1920s and ‘70s. Walt Disney must be mad with envy. Around his crazily eclectic all-sorts of campaniles and Cornish cottages, memories of Portugal and Wales and heaven knows where, C W-E planted every plant that loves mild seaside air, a whole wood full of wonders, and hydrangeas in thousands.

I come home to our workaday woods with my head full of plans that will come to nothing. Of a little New Zealand or a Sintra, a Santa Barbara indeed of exotic shrubs and flowers. Sheer folly. Nothing could be lovelier than the forest around me.

There are colours in fading hydrangeas that give me a little shock of pleasure every summer. The showiest of late summer flowers clearly have pigment problems; acid soil sends them one way, limey soil in the opposite direction. But all their pigmentation seems unstable. They can start out white and turn pink, or pink and go red, or blue and turn mauve or purple, And as they fade, in many cases, their pigment can disappear altogether, leaving a pale parchmenty ghost.

The pigments involved are the usual suspects: anthocyanins of various hues. The hydrangea’s chromatic weakness – which I rather see as a strength – is that its sepals (petals to me, but Trad is a stickler for scientific accuracy) only have pigment in one layer of cells. When they fade, that’s it. But what images their washed colours evoke. The paint on beach huts untouched for years in all weathers, tiny babies’ wrappings, dowagers’ shawls…..

How utterly different from their contemporaries the salvias. Salvias do primary colours. Is there anything redder than S elegans or splendens, or bluer than S. patens? There is a good buttery yellow in S. madrensis, and lots of subtle shading in between. S. leucantha encroaches on hydrangea territory, and S turkestanica is pretty ambivalent. As the hydrangeas fade the central American salvias get in to their stride. The one I wait most eagerly to see is van Houttei, part dusky scarlet, part maroon – and in flower for months on end.

It was the nursery that clinched it. We were house-hunting in London in March, in the dreary grey weeks when the East wind blew unrelenting day after day. One house had ticked the boxes, only to be taken off the market; others were laughably unsuitable in various ways. One icy day we visited a house in a street we didn’t know at all, to be welcomed into warm, well-lit, totally comfortable surroundings, decorated (said my wife) rather like an old-fashioned luxury hotel. Yes, I said, we could live here without even talking to a builder – though a chat with a decorator would be good. ‘It’s not really us’ said Judy.

Next day she went back on her own to case the unfamiliar neighbourhood. Yes, there were cafes, cleaners, a Waitrose, delis – and just across the main road, only 100 yards from the front door of the house under discussion, a flower shop occupying the ground floor of a rambling old house. Inside, the scent of flowers was intoxicating. It was instant spring – and led, through the back door, into an Aladdin’s garden, wintry though it was, of potted plants, potted trees, potted shrubs…an entire nursery. Narrow paths under tall planes lead the length of a film-set Georgian square – all nursery. She had found Rassell’s. We bought the house.

Rassell’s nursery, in Earls Court Road, goes back to the days when the road was a country lane leading to Holland House through Lord Kensington’s farmland. His lordship, apparently, started to lease his fields to developers to pay his gambling debts (this was the early 19th century). His old lodge house on Earls’ Court Lane he leased to a nurseryman, and in 1870 Henry Rassell from Sussex came on the scene. In 1897 he acquired the freehold of Pembroke Square (everyone else had to make do with a lease), opened his florist’s shop, and started the business which is still there. I pop in for something almost every day – if only for the sight and smell of hundreds of happy plants.

This is the rose pergola we are putting up in the Fellows Garden of King’s College, Cambridge in memory of my father, Guy, who went up to to King’s as an undergraduate one hundred years ago, survived four years at the Front, and returned in 1919 to finish his law degree.

In the autumn we will be planting the roses. If you have good experiences of varieties for pergolas, (the soil is light, the climate dry) do please share them.

We’re just back from a seaside holiday, this year perfectly timed for two weeks of perfect summer, when simmering in London is not the connoisseur’s choice.

The temperature on the Solent, with a steady westerly breeze over Christchurch Bay, was five Celsius degrees lower than on the commons of the New Forest five miles inland. I am discovering the pleasures of a seaside garden – not, I’m glad to say, one totally exposed to wind and spray on a beach, but walled and sheltered by the little house, with the sea over the saltmarshes at high tide only sixty yards away. The air is heady with the scents of seaweed and saltgrass and tidal mud, and luminous with ocean light.

There is such a rewarding template for seaside gardening that there seems no point in being original. What’s wrong with hydrangeas and montbretia, and fuchsias and thrift? But drought can be a serious worry; the soil is basically sand and gravel and shingle and rain often seems to skip the beach to fall inland.

When we arrived I had the deep joy of watering a parched garden. I turned the rusty tap on the water butt and heard the jangling of stored life and energy that had only been breeding mosquitos as it filled my can. As I watered I was cutting down the top hamper of everything that had flowered and withered. Water and fertilizer would bring a second flowering – of some things. Or at least a fresh covering of leaves.

The garden is about 40 feet square, two-thirds paved, more dedicated to sunbathing and guzzling seafood than to horticulture. It has a campsis-choked pergola but otherwise no shade; apart from one raised bed the planting has almost all been low-growing. The house wall supports a climbing hydrangea; there are capabilities here.

At first I thought of a tree, maybe a pine, in the central brick-edged bed. Then I remembered a plant I was given by Cedric Morris in Suffolk many years ago; almost the only woody plant, as I remember, in his great open iris beds, a shrub growing perhaps seven feet high with a propensity to sucker – could this be why he gave it away so freely? It is Elaeagnus commutata or silverberry, a North American native used for its nitrogen-fixing abilities in dreadful soil.

In the narrow garden facing the sea, between house and road, I have planted agapanthus and Hydrangea quercifolia – a favourite in my daughter’s Riviera garden where it grows huge, flowers wonderfully and colours like a furnace in autumn. I don’t expect such a performance in Hampshire. It drank the water from the butt like a desert traveller, though.