Green Provence is another country. The tawny arable plain painted by Van Gogh gives way, east of Aix and Mont Ste Victoire, to a fresh green (a pale, almost apple green) forest of pines covering endless confused hills. They are Aleppo pines, sinuous, pale-trunked, with needles in pairs, found largely along the Mediterranean coast. Off to the south the Massif des Maures shelters the bays of the Corniche: Le Lavendou and St Tropez. Green Provence keeps going, a forest to the horizon interspersed with insubstantial towns; Brignoles and Draguignan the biggest. Quiet villages of buff and ochre houses are clustered around with olive groves and patches of vines never big enough to suggest an industry.

A lazy little river, the Argens, as silvery as its name suggests, winds slowly east to the Mediterranean at Fréjus. Correns, one of the villages on its course has distinguished itself by being the first commune in France to declare itself entirely ‘Bio.’ I am writing this there, in a little rather stiff-looking chateau facing south down to the river, its wide gravel terrace, dedicated to boules, shaded by magnificent pollard plane trees that could be its contemporaries. They cast huge shadows on its yellow walls and fourteen grey-shuttered windows. Its provincial formality evokes the novels of Flaubert and Balzac. What domestic dramas, what frustrated passions have its tall ceilings seen, and heard the slamming of its panelled doors?

An amphitheatre of low hills forms a barrier to the dreaded Mistral cutting down from the north. The forest here burned a few years ago, laying bare a pattern of buff stone terraces, gradually greening as the maquis takes over again. The house and garden sit on three steep-terraced levels, their stillness tinkled into life by the spring that must have inspired the builder to settle here.

The flora of a Provencal garden is predictable; a reassuring sameness of olive and vine and almond, fig trees and plane trees. In old properties the plane trees are multi-stemmed monsters mottled yellow and grey. Dark cypresses can be either the classic rocket shape or branchy and nondescript. In this garden they vary from nondescript to so severely, tightly, narrow it is hard to believe no wire corset is involved. Rosemary, lavender and cistus are the predominant low shrubs. A belt of grey olive trees surrounds the garden. Then the green monotony of vines.

You could have taken it for one of the many vineyards appearing all over Essex, taking advantage of the country’s sunshine records.  But no: they’re blackcurrant bushes, rank upon rank, acre upon acre. I had never wondered where Ribena comes from; now I know. It’s the valley of the river Blackwater, a lazy stream that starts as the Pant, becomes the Brain, then changes its name once more and finally meets the Thames Estuary between Maldon and West  Mersea in a flurry of activity: oysters, salt production and celebrities. The tidal causeway to Osea Island is familiar to singers using its recording studios.

We lived in Essex for forty years. We learned to counter its reputation as a flat and boring county. ‘No’, we used to say ‘Its undulating and boring.’ It certainly undulates, silver cricket bat willows marking the low points, its water courses, while its boredom is relieved by village streets of ancient gabled houses plastered in many colours.

In the water meadows along the river you wade through the lush grass, your knees soaked, scarcely able to tell where the grass ends and the weed-choked water begins, your head snared by the congestion of willows. Ratty would love it. Perhaps this is where he and his friends live.

We stayed with friends who cultivate blackcurrants in large numbers and provoke my envy in possessing a thing I have longed for all my life: a gushing spring at the top of the garden. The last bit is the most important. A spring at the bottom will give you a fine pond; possibly a stream. At the top it gives you all the energy of falling water. Theirs fills a calm broad pond, then overflows over a little wooden waterwheel  into a tumbling brook to another pond, and then another, until it slithers through the willows into the tall grass and into the Blackwater.

In our Welsh woods we have water rushing over rocks, wild, glittering, noisy, untameable. My urge is to placate it, put a dam in its way, tranquilize it; arrest all that urgency. It is the converse of my poking about with stick and leaves to induce a tiny stream. Idleness (mine) meets elemental energy and treats it as a toy.

How we come to have a wild lettuce in our tiny front garden I don’t know, but at ten feet high there is no ignoring it. Lactuca virosa is its name. At first, in March, it looked rather like a stripling primrose, with long oblong slightly toothed leaves. These mounded up, and by April clearly had higher ambitions. It grew steadily, its long leaves at intervals of a foot or so on its straight stem. It had a useful prop in the myrtle supported by our neighbour’s wall. At ten feet or so it produced an impressive panicle of tiny yellow flowers quickly followed by fluffy seedheads a little like clematis seeds,

Sadly it tastes bitter. No, worse than that. I shan’t be exploring its supposed psychedelic properties. But I wonder where it came from.

I’m wondering whether to get the locals round to have a grand tomato harvest and pick all four in one day. Maybe bonsai tomato-growing is not the ideal, but this year it just happened. I forgot to pot them on from a four-inch pot; they looked sweet on the bench next to a pansy and the heliotrope I keep for an intoxicating sniff now and then. Now those little red globes are beckoning. Is home-grown produce really the best?

Tomatoes are a major theme in July, and not just a domestic one. They are tumbling in from all sides; the Isle of Wight conspicuously in the lead, in a bewildering mix of changes and colours. There is still little to challenge Gardener’s Delight for an instant pop in the month, but salads are a different matter. I made a bold bicoloured one yesterday: beefy yellow and purple, roundly ridged, mostly flesh with little juice. Interleaved slices on a flat dish looked intriguing, but what made the dish was the Sicilian olive oil, the scatter of sea salt and a few leaves of basil from the pot that always reminds me of poor Isabella, so often painted by pre-Raphaelites in search of beauty in mourning. Basil seems preordained for tomatoes. Rosetti could have painted glowing tomatoes with the lush leaves of drooping basil, and Tennyson written ‘with blackest moss the flowerpots were thickly crusted one and all. The rusted nails fell from the knots that tied the tomatoes to the greenhouse wall’.

But did Tennyson have tomatoes? It was only in 1820 that one Robert Johnson publicly proved they were not poisonous by eating one at a New Jersey courthouse. What a scarlet tsunami he unleashed.

How rarely I get north of Watford, let alone as far as Cumbria. It was only for a few days, but long enough to revisit the paradigm of topiary, Levens Hall, with its crazy toppling yews, and to discover the Holker (pronounced “Hooker’) estate on the remote peninsula of Furness. Furness has Morecambe Bay to the south, the Coniston Fells of the Lake District as a jagged frieze to the north, Barrow (where we build our submarines) to the west and not far off the vast ruins of Furness Abbey.

The Cistercians chose remote sites, but built with brio. Furness was founded by King Stephen, grandson of William the Conqueror, almost on the scale of Fountains Abbey, with a similar heart-breaking remnant of its soaring vaults and scarcely readable scraps of the monks’ quarters. It lies in a shallow green valley in the woods, a little river supplying all its plumbing. The stone is rusty red, the feeling of abandonment overwhelming. In places like this I still feel rising fury at the crimes of our most criminal king. Henry VIII stole or destroyed the culture of centuries, its greatest works of art and hundreds of its most educated souls. The evidence in abandoned foundations like this is not very much more than we have of Ancient Egypt. The shame hangs in the air.

Bare ruined choirs…

People still ask me, ten years after we left our old Essex house, Saling Hall and the garden we made there over forty two years, ‘Don’t you miss it?’

The answer is no, or not really. But why not? In the first place because we are happy in London, with all its amenities (especially its parks), but principally because memory works so well. I can still take mental walks, not just at Saling, but in all the gardens and places I’ve known well and been attached to. In fact it’s what I do when my head hits the pillow. I can visit our woods in Wales, or our daughter’s garden in Hampshire, Wisley, or the garden of a chateau in the Médoc where I had a hand in the design, or stroll as I often do in Kensington Gardens, where trying to match the dogs with their owners is a game I sometimes play.

The other reason our Essex garden remains fresh, and even exciting, in my mind is because our successors there are doing such a good job with it. Not perhaps exactly what I was planning to do, but intelligent, interesting and above all pretty. The walled garden has not looked so good or been so well maintained since our early years there and its complete replanting in the early 1970s, or at least since Christopher Bailes joined us as a very young gardener – en route for his illustrious career at Merrist Wood, the RHS gardens, and eventually Kew.

It was a risk, I admit, hiring a young man whose experience didn’t go much further than leaf-sweeping, but when he sat on a bench with me at Saling, in the walled garden, and said ‘I would just love to garden here’, something told me he’d work hard and do well. After a few weeks, when he asked to borrow my gardening books, I knew for certain. But not that one day he’d be in charge of the orchids at Kew. Now I read his books on orchids, and hollies, and feel quite proprietorial. The RHS has given him its Victoria Medal of Honour. You can’t get more senior than that.

It’s not just the roses that are loving this summer. The pubs are having a field day on their pavement extensions; clear proof of global warming. Ten years ago a pint outside huddled near the door constituted London summer. Now they have built permanent terraces on the pavement and in parking spaces. Do they pay parking charges?

Kensington smells of the “Confederate Jasmine” that has become a signature climber on its garden walls. The name was given to Trachelospermum Jasminoides because it grows south of the Mason Dixon Line, the frontier of the Confederacy in the American Civil War. In this street it lushes out so far from a garden wall that you have to make a detour round it. Its variegated form scrambles over the little balustrades across our garden, while I cut off shoots three feet long.

Warmth is what plants want to speed their growth, even more than water. It’s not just roses that are growing fit to bust. And flowering as we’ve never seen them before. Everything from our lemon tree in its pot to the creeping campanula that has become a London weed is jutting out shoots twice the normal length covered with flowers. Agapanthus is almost arborescent. Two blue-flowering bushes I specially treasure are painting the garden the colour that is rare in summer: Lycianthes (alias Solanum) rantonnettii is tall enough to shade the greenhouse and Acnistus (alias Iochroma) australis dangles its elegant soft-blue bulbs, fit for a painting of fairies.

There is a downside to these exotic excesses: an ugly rash of banana plants dwarfing front gardens with this gross and tatty leaves. Not everything you could grow is beautiful.

What has given roses (and not only roses) such a boost this year? Bushes that routinely put on a respectable show have gone into overdrive with heavy trusses of flowers. Roses are falling from high in our sycamore. I feel like the guests at the feast of Heliogabalus in Alma Tadema’s painting being smothered under cascading flowers. Somehow the seasons, from the heat of Last August, through a kindly winter and soaking March, have engineered the perfect rose-storm. Dead-heading has already filled the Council’s blue bags again and again. Where does the Council compost all this fragrant material? In Kensington the shameful answer is that it doesn’t. It burns it.