You could say that my sister is keen on tomatoes – though ‘obsessed with’ is closer to the fact. They’ve had perfect growing conditions this month. Jack’s beanstalk gives the idea. I suggest pinching out some axial shoots and discouraging growth above the garden wall. “Hands off’, she tells me. ‘Don’t touch them’.

An Italian visitor turns up. ‘Your tomatoes are out of control’ he says and pinches out precisely what I was banned from pinching. A prophet is not without honour…..

The weather this year is making even the indifferent aware that nature has moods that can make life uncomfortable. Places that are almost bywords for pleasant living and delicious produce have gone up in smoke.

It has been agonising to watch fire racing through forests and laying waste to people’s homes and livings. There has long been a green lobby urging us to take care of our world. It was christened Only One Earth generations ago. I was fortunate to know one of its principal protagonists in this country: Dame Barbara Ward and will never forget a summer night that a few of us spent walking round Possingworth lake in Sussex. I was learning to feel a part of nature.

Of course, it’s much harder to feel in London. We appreciate our parks alright, but how much thought do Londoners give to the trees that shade us and the green spaces where we can rest our eyes and minds?

The MPGA was founded (by a forebear of my father’s friend Lord Brabazon) getting on for two hundred years ago. Its impossible to say how much less green it would be without what the MPGA has been able to do, but nobody can deny it’s been worth doing, its results are all around us, and they help to make London the wonderful place it is to live and work.

We all know this. We also know it’s our responsibility to keep planting, to nurture our green assets and to add to them. It’s not enough to be passive and sit under trees. Our children and their children need more.

The shingle at Keyhaven seems designed to discourage you from going in for a swim. All its edges are sharp. The water though is inviting; lazy wavelets from the calm strait between Hurst Castle and the Isle of Wight. Hurst Castle is the impressive guardian of the narrow western entrance of the Solent, a mere mile wide but a swim not advised when the Solent’s tricky tide is flooding by. But there is nothing like the traffic here that keeps the eastern approach by Portsmouth so busy.

Keyhaven remains a little fishing port, with seven or eight boats going out round the Needles, often, I’m told, to harvest cockles, of all things. The market for tons of cockles? Apparently Korea can’t get enough. The village has a good pub, The Gun Inn, and a huge car park. Hawker’s Cottage, near the pub, is where the extraordinary diarist, wildfowler and inventor Colonel Peter Hawker lived.

Hawker limped from a wound in the Crimean War, but before dawn in January he and his man would go out with their guns, wading through deep mud to slaughter incredible numbers of birds. He also regularly taught piano in Paris at the opera house by a new method of his own, travelling from Southampton to Cherbourg and by train via Rouen to Paris. He took his latest design of a breach-loading rifle to the Great Exhibition, standing in the opening queue every morning to demonstrate it; Prince Albert showed it to the War Office, which adopted it.  Do read his diaries.

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.