Perhaps finishing schools have finally finished. I no longer circulate in the milieu of debs, their delights, coming out dances and girls being ‘finished’, ready for the Season, the husband-hunt. Does it still exist?

I ask because we have just been staying at Hartwell House, near Aylesbury, where it happens my sister Pauline, ten years older than me, was ‘finished’ before going on, not to marry a deb’s delight, but to travel the world, to work as a stewardess for BOAC and eventually to marry a brewer (whose brewery you pass in Chiswick on the way to the M4).

Hartwell House has lots of ‘previous’. In the aftermath of the Napoleonic wars it was leased to one of France’s last (and apparently its fattest) kings. Louis XVIII was, shall we say, picky about his food. His substantial staff at Hartwell included a predegustateur. I described his job in Trad in July 2015. Be assured no gritty pear or tough-skinned apple ever reached his majesty’s lips. The orchard where these perfect fruits were grown is still within the walls at Hartwell. By a miracle the vast scar of HS2, the folly railway, just misses the park before going on to devastate the Lee, the lovely estate of the Stewart-Liberty family.

Hartwell is, by what seems another miracle, in the care of Historic House Hotels, a work of extraordinary philanthropy that is preserving and putting to good use three important houses. The others are Middlethorpe Hall on York racecourse and Bodysgallen near Conwy in Snowdonia, or Eryri as we are now supposed to say. All three houses were bought, restored, furnished with antiques and given to the National Trust as a going concern (not without the pool and spa everyone expects these days). The Trust can run a hotel as well as any country house. Indeed their standards are so high that you could still believe the old regime was still going strong. Talk to the swan permanently stationed by the front door, or the cattle or the sheep that nosey up for a chat. Or the carp that formation-swim under the stone bridge. Hartwell seems to exist in an older world.

When we had plenty of space to play about with ideas (240 acres in the neglected centre of France) I went in for a spot of rewilding. I’m not sure the term existed in the 1970s, but the reality did wherever you lost control – in this case of what is known in France as ‘friche’. The dictionary translates it as ‘wasteland’, ‘fallow land’ or ‘wilderness’; in other words land that is surplus to requirements and that nobody bothers with. It is where you find out the true natural destiny of the land. In those years on our neglected farm we learned a lot.

To learn more I tried a number of experiments. I fenced off an acre or two of low-level friche; recently abandoned, I supposed, either from use producing small poles or from grazing. It didn’t take long for plenty of seedling trees to emerge from the inevitable pioneering brambles, which have the virtue of protecting them in their infancy. The saplings were almost all either hornbeam or oak. Left to grow, I reckon the eventual woodland would have been eighty or ninety per cent hornbeam.

Rewilding, then, strictly left to its own devices, will in the long run give us back the woodland that once covered the country. Plus, no doubt, an interesting selection of presumptuous exotics.

“Plagiarize; let no one else’s work evade your eyes.’ Who remembers the wicked wit of Tom Lehrer ? He puts it harshly, but the fact is that all writers feed on what others have written.

I frequently scroll through my memories of Shakespeare. Othello crops up often. “If it were now to die, ‘twere now to be most happy’ clicks in at moments of intense pleasure. Even just on smelling a rose. The sense of smell momentarily takes over from all other sensations, and even thoughts. If the olfactory nerve is closest to the memory (as I’ve been told) perhaps that includes a cut-off switch for the rest of the brain.

The rose we call ‘Mad Alf’ has scrambled twelve feet up the sycamore at the end of this garden. One hopes that Madame Alfred was as fragrant as the marvellous rose that has made her (or her name) immortal.

I still had my nose buried in her bosom at nine last night. There was complete stillness, even here, in the heart of London, but for the faint trickling of water into the little fish tank. Alas, for the moment, no fish. The heron from, presumably, Kensington Gardens, stole our little Cae and Gwian (named after our. wood in Wales). How he spotted them is a mystery. Their tank is half-buried in viburnum and ivy; its water surface only four feet by one and a half. I’m off to find their replacements; perhaps ones in camouflage colours.

Tulip Bleu Aimable in a Gravetye border

William Robinson could be called the grandfather of modern gardening, with John Claudius Loudon as great grandfather. Loudon’s work is pretty remote today: Robinson’s though is among us still, (he founded, with Gertrude Jekyll, the original The Garden magazine) and at his own house, Gravetye Manor, is palpable and ready for us to admire.

Gravetye is now a luxurious hotel. It’s Robinsonian origins and detailed story are precisely spelt out, and plants he describes in his writings lovingly preserved and reproduced. He died here in the year I was born: the grandfather feeling is not inherently absurd.

As a lad in Ireland in the 1880s he worked in the gardens of Curraghmore, near Waterford, the estate of the Beresfords, Marquesses of Waterford, where my own great great great grandfather Owen Johnson was steward in charge of the estate in the 1830s. It’s not impossible that grandpa and Robinson shared a pot of tea.

Gravetye before Robinson’s arrival was almost a wreck, the house not lived in, the grounds overgrown. Characteristically he recorded everything he did in modernizing and beautifying the hundreds of acres, planting thousands of trees to create what are now maturing beech and oak woods. From the terraces of the house, indeed, the views are entirely Robinson’s creation. The terraces look down on the lake he created. Higher on the hillside is his circular walled kitchen garden, now again in applepie order. Credit for the initial restoration belongs to Peter Herbert, formerly of the De Vere Hotel in Kensington.

All round the house itself you walk through degrees of what Robinson called ‘wild’ gardening – though the walled garden west of the house is scarcely what anyone else would call wild. Tulips are something of a speciality here. In April they dominate the borders near the house (the dining room is separated from them only by a simple glass wall). Blue is not a common colour in tulips, but a lovely one new to me called Bleu Aimable is now on my list of bulbs to plant this autumn.

 The road home to London from Snowdonia and our Welsh woods is long and winding. There was a blizzard of sleet as we threaded our way along the lovely green valley of the River Elan. We arrived with deep pleasure at our overnight stop, precisely on the English border and my favourite garden for half a century. Yes, Hergest Croft.

I see I first wrote in this diary about Hergest Croft in the 1970s, when the third of the five generations of the Banks family was in charge. The fourth, my friend Lawrence, my contemporary at Rugby and Treasurer of the RHS, is succeeded by his widow Elizabeth and their son Edward. They are quite a family. Elizabeth was the first professional landscape architect (her briefs included the Royal Parks) to become RHS President.

From the elegant new bungalow in the garden she calls her ‘enderhome’ she supervises a garden that summarises all the amenities of traditional country house walled gardens, and leads on into one of the country’s most distinguished collections of trees and shrubs, flourishing, fascinating, and mostly rare.

A further walk through rolling parkland takes you to Park Wood, a place sacred to me as where I first conceived my passion for trees. It was Lawrence’s father Dick who inducted me; tall, benign and omniscient, he introduced me to birch and silver fir as one does a friend. Streams and pools reflect the soaring larch and oak, a hundred feet above, with the red flowers of rhododendron arboreum mingling in the intricate canopy. Bright green and yellow skunk cabbage circles the pools where a frog plops and a flower drops from high above.

Trad is not only a single-minded scribbler, he has been known to actually do some gardening, and even had a go at designing gardens. Half of them have been in France, though intervention would in most cases be a truer word than design. Several of them are related to Trad’s other obsession, wines.

Only one has been on a landscape scale; my absurdly ambitious attempt to transform the fields, woods and riverside of a more or less abandoned farm, some 240 acres in all, into a unified and recognizable ‘landskip’. It had the potential: the west slope of a small river valley facing, on the eastern crest, the traces of a Roman oppidum, its earthen ramparts still apparent. The slope was a typical forest of the centre of France, largely a mixture of oak and cherry and hornbeam, until its latest owner felled the tall wild cherries and left their trunks in rotting heaps (having no idea how to sell them).

The numbskull then tried to extract the oaks but was largely frustrated by the steepness of the land. His predecessors had more sense; they converted them to charcoal, a process that removes ninety per cent of the weight and maintains most of the value. Every twenty metres through the wood a wide black circle showed where a charcoal clamp had been. I pictured the scene fifty years before; the woodland noisy and smoky, loud with voices and axe blows, donkeys or mules ferrying the charcoal out to a wagon on the track at the top.

The little river Aumance at the bottom was too shallow to be much use. In spring it could float the raft we made of an old barn door, down past a sturdy little chateau to Vallon en Sully. The chateau (manoir is more accurate) has a stone plaque on the gateway claiming that it was the eastern most limit of an English advance from Gascony in the Hundred Years War.

Much of the farm was in a revolting state, covered with scraps of the black plastic used for covering straw bales and fiendish strands of barbed wire. Its recovery is entirely due to the generously constructive French system of grants. I wrote to the departmental office of the Eaux et Forets, the department of state established by the genius of Jean Baptiste Colbert under Louis XIV. The reply came from the boss in Moulins, the ‘country town’, Alain Maciare, who in due course became a firm friend and the source of funds I never expected. Effectively the French government subsidised my ambition to turn our scrapy property into the dignity of a ‘domaine’.

Pale purple magnolia globes are nodding in the wind outside the front window, and their petals falling far too soon on the paving in the front yard. They have banana-skin propensities; I have to keep sweeping them up. It’s strange to think that this extravagant flower was apparently an early arrival in the course of evolution. They don’t seem to be good at attracting insects; there are none in sight. Their fleshy petals, it seems, were designed – if that’s the word – as food for beetles. Flowers became more economical as nature grew up; just look at the tiny red dots on an oak.

Is this the most showy spring for years? So it seems, looking along the street at explosions of pink and white in cherries and magnolias. I always wonder who splashed out on Kensington’s floribundance. The comparative austerity (and superior elegance) of our neighbour’s Cercidiphyllum – Katsura to its friends – could almost be seen as a piece of snobbery.

Meanwhile a strong west wind (odd: surely it should be east) keeps coat collars turned up, and garden pottering is rather discouraged by what seems almost constant chopper noise. I suspected Kensington Palace, half a mile away, of causing the nuisance, but surely they don’t fly off every twenty minutes. So at present I am just looking out of the windows to see what’s in flower. The white flowering currant bush, Ribes sanguineum White Icicle, is the eye-catcher of the moment. After ten years it measures seven feet high and wide. Behind on the wall Chaenomeles speciosa Nivalis keeps the white theme going; then there’s a white Bergenia and a pot of Ipheion uniflorum. Not much colour, it’s true. Camellia alba Simplex is another cool customer, but we inherited a big bushy Camellia ‘Top Hat’ which is generous with pink petals. It’s spring alright, but not shirtsleeves yet.

Who do we have to thank for the splendid variety of trees that adorn our local streets and parks?

Not everyone looks at, or even notices, the trees they walk under everyday. Perhaps in April when they light up with blossom and scatter confetti on every car. Perhaps in September when they begin to cover the pavement with potentially treacherous leaves.We rarely thank them, though, for the grace of their branches against the sky and the welcome shade they offer on a hot sunny day. Our part of Kensington is blessed with more trees, and mote different kinds of trees, than most, from the stately planes that give Pembroke Square its special dignity, to flowering cherries that for a few weeks in spring completely change the mood of otherwise unexceptional streets. Planes and cherries are commonplace; the bread and butter of street planting. The council’s tree officers, though, are doing a more imaginative job.

We live in Scarsdale Villas, which already has the advantage of being a double-width street. It was part of the property that Lord Kensington (of Holland House) sold to developers in the early years of Queen Victoria. One of these speculators had property in South Wales – hence our cluster of Pembrokes (square, road, villas…). Viscount Scarsdale had a mansion approximately where High Street Kensington station now stands. (Sutton Scarsdale, his seat in Derbyshire, is now a baroque shell, its rooms in a museum in Philadelphia.)

This doesn’t answer, though, the question of why we are so well endowed  with trees. One of our biggest and best is a common ash which stands in the middle of the private Edwardes Square, hence hidden from public view. I suspect it may date from the creation of the square just after the Battle of Waterloo. (They say many of its first residents were the families of captured French officers). Long may it be spared from the die-back which is killing ashes round the country.

Two other huge specimens in our streets are the so-called Tree of Heaven (heaven knows why), Ailanthus altissima, originally from China. Others call it the tree from hell; it can produce overwhelming numbers of suckers from its roots. One stands on the corner of Abingdon Road and Stratford Road, mercifully not – or not yet – sending up suckers. Another, a tall straight specimen, is on the corner of Edwardes Square nearest the Scarsdale Tavern. Their ash-like pinnate leaves have a distinct smell of onions.

Scarsdale Villas is almost a linear arboretum, or ‘dog’s dinner’ as one council officer describes it. I have still to identify some of its ingredients. A fine Zelkova serrata, from the Caucasus, is an unlikely tree to plant in a street, being characteristically as wide as it’s high. There are plenty of beauties, though. I am only disappointed by the council’s recent planting of amelanchiers, charming light-weights that will never make fine tall shade trees. The best advice for planting street trees is to stick to the tried and tested; the classics.     There is a reason why the great Platanus x hispanica is called by  this formal botanical name. It has no native country. It is a hybrid between the talismanic Chennar tree of the East and the rare (in Europe) American native plane. Did the marriage happen in Spain, as the name suggests? Nobody seems to know.