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.

Pinus halepensis dominates the scratchy scrub

La rentrée is the French term for it: the back to school end of summer when French roads are jammed with cars leaving the beaches and mountains. There is no notion of dawdling, of spinning out the last few days, even if only to avoid the nose-to-tail roads. The sense of a sudden descent from holiday nirvana to dull routine, with a year to wait before the next escape, is deep in the French psyche. And funnily enough the last Saturday in August often sees the weather change in sympathy.

Suddenly you are aware that the sun is too low in the sky. Driving west at teatime is irksome. The dark closes in before you are ready for it. Suddenly the cry goes up ‘J’ai froid, chéri. Mon châle’. And leaves detach themselves one by one from the plane trees and rattle to the ground.

This year the grape harvest is early, healthy and plentiful, a smiling vintage promising lots of good ripe wine from coast to coast. Winter was mild, spring early, the summer hot and dry with enough rain in August to swell the berries. Picking grapes is always hard work, but there has been a party atmosphere in the upmarket vineyards where they still pick by hand; in the rest the towering yellow picking machines have been roaring all day long.

We are in La Provence Verte, the Provence north of the A8, of high ridges and deep limestone clefts where vines occupy enclaves of flat land hemmed in by forest. The dominant tree, and the one that gives the woods their startling greenness even at the end of a hot summer, is the Aleppo pine, its name taken from the now-tragic Syrian city (although it is a native all round the western Mediterranean). Drought doesn’t bother this surprisingly delicate-looking tree with long slender needles, two to a bunch, of something between apple and lime green. They are graceful and soft to the touch and form an airy canopy on trunks that are often sinuous. Round habitations they are joined by the dark verticals of cypress and a few evergreen oaks.

I’m never sure whether the ground flora is properly called garrigue or maquis; I think it depends on whether the soil is acid or alkaline. This is limestone, and relatively fertile to judge by the thickness of the scrub, the height of some of the trees and the number of seedlings. Where it thins out and bare patches appear I’m told we can put it down to allelopathy (related, perhaps, to allergy); the effect plants can have of inhibiting their rivals for space or nutrients through their roots, their volatile components (there are plenty here, with resinous leaves in hot sun) or by what happens when their leaves decompose on the ground. I’d heard of juglone, the unfriendly substance produced by black walnuts; and eucalyptus often seems to poison the soil around, but didn’t know the same was true of so many components of maquis (or garrigue). The effect, in any case, is the scratchy scattering of scented plants that includes the prickly little kermes oak, juniper, cistus, mastic (aka lentiscus), thyme, lavender and masses of rosemary.

The more I go back to our woods in Wales, the more I regret the need for conifers. Above all for Sitka spruce. Nothing creates useful strong timber so fast: joists, rafters, floor boards… Nothing else will make sour boggy land productive. And yet its black, prickly presence (don’t try to touch a shoot – even a young one) makes our forests grim, forbidding places. Back in the 1960s the Forestry Commission actually tried to kill off our lovely mature oak woodland by underplanting the oak with spruce. As they grew (sometimes as much as five feet a year), they starved the oaks of light. Their lower branches died. Their tops sometimes survived, struggling upwards among the dark spears of the Sitka.

But the native flora below, the oxalis, mosses and ferns, wild raspberry, bilberry, feathery grasses, sometimes bluebells, that signify ancient oak woodland was gradually eliminated, replaced by a brown needle carpet with the occasional fern.

We have been able to salvage several remnants of the old woodland by felling and removing the conifers, but they are a pitiable sight. We plant new broadleaves, oak and beech, among the scrawny old trees, hoping our piety will be rewarded. Conifers are so fertile, though, that their self-sown offspring outgrow our new plantations – and weeding them out is a painful process. Larches I don’t mind (and in fact I love the pale, fragile-looking saplings; being deciduous they are less of a challenge to broadleaves). Sitka, Douglas fir, the useless lodgepole pine, the handsome but economically hopeless western hemlock and the worse-than-useless Lawson cypress are just pests.

The other perennial pest is bracken. It seems much more invasive since foot and mouth disease drastically reduced the number of livestock on the land. It covers stretches of hill that were grass with heather and bilberries with its dull blanket. It has always been a problem here in Snowdonia. Farmers’ letters and diaries of two hundred years ago complain of the August drudgery of cutting and gathering it – at least it made good bedding – under the hot sun. They didn’t know as they breathed its dust and spores that they are carcinogenic. The one herbicide that kills it is difficult to obtain and difficult to apply. And yet the hills are beautiful. I climb them to look out into the wind and the clouds towards Ireland and feel grateful to be alive.

It’s three weeks now since we spotted the box caterpillar (or rather its trail of destruction) in the garden, We’ve sprayed the affected bushes three times – and the funny thing is we haven’t yet seen either a caterpillar, a larva or a moth. Their traces are here all right; threadbare patches in the box with telltale tiny webs. The worst is the lower half of a pyramid which is heavily shaded in a wall corner. Could its position have something to do with it?

Meanwhile news comes in from friend after friend in London; serious infestations. The moth must be a fast flyer – it seems to land everywhere. I continue to spray – specially inside the plants. I wear rubber gloves and tease the branches apart to spray the inner branches. Encouragingly there seem to be quite a lot of new leaves sprouting nearer the trunk. If the pest has taken a break for the winter I’d love to know where it’s hiding.

STOP PRESS: A gardener in Provence has been fighting the caterpillar with pheromone moth traps (yellow, sticky) and regular spraying.

Things are not looking too good in the garden just now. There’s a scaffolding tower blocking the outside staircase down from the ground floor, five feet of our Victorian garden wall has been demolished, the trellis with our laboriously trained trachelospermum has been removed and everything is covered in a thick layer of dust, The noise of drilling and hammering starts at eight and goes on till six; the noise of pumping water up from the basement depths goes on all night.

The roses and agapanthus, the geraniums and anemones, the fuchsias and salvias, the lemons and oleander, the clematis and solanum, the kirengeshoma, the thalictrums and my pretty ferns are all pretty in vain. Nobody’s looking. We don’t even open the door – except to dash to the shrouded greenhouse in hope of a ripe tomato (I picked my first Gardener’s Delight yesterday).

What’s it all about? This is London life in the wake of the Party Wall Act 1996. It’s your property; you can do what you like on it and the neighbours can just grin and bear it.

To do them justice the twenty Bulgarian workmen who assemble every morning at seven in our neighbour’s garden are a cheerful crowd and seem to work as fast and as tidily as they can. What they would do without a pretty big garden as their assembly point, canteen and depot I can’t imagine; there certainly isn’t room in the street.But the rage for basements is out of control. In the next street one terrace house is in a basement sandwich with hoardings up on both sides and lorries queuing to cart off their neighbours’ rubble. The Council? They are hamstrung, they say, by the Party Wall Act. They can’t disallow ‘development’ – or even police it. Not enough enforcement staff…. there are plenty of excuses.

We’ve visited a couple of basement developments. One consisted of eight featureless rooms, all painted this season’s grey, dubbed ‘Media Room’, ‘Gym’, ‘Office’, ‘Bedroom’, ‘Wet Room’, ‘Meditation Area’. Upstairs was a perfectly nice Victorian house – until they took our all the cornices, mouldings and everything that gave it character – and of course painted it all grey. Gardening? The developers opposite used a crane to heave four mature Italian cypresses right over the house to plant then in the diminutive back garden. They died, unwatered, within six weeks. And what happens underground in a power cut?

It’s all justified, it seems, by the price of any space in London. Add 1,000 square feet, even underground, and you’ll be in pocket for more than twice what it costs. Your neighbours can lump it; that’s what the Act says.

Thalictrum delavayii at Saling Hall

Thalictrum delavayii is my plant of the summer. I planted it last year at the top of the steps leading up from the kitchen door; so far there is only one main shoot, now nearly seven feet high, like an impossibly delicate tree with lilac leaves, each leaf a flower like a tiny nodding clematis. The cloud of flowers is at eye level as I reach the top step, and from the kitchen window it is as important as the trees beyond, a lilac filter for the view of the rest of the garden.

‘delavayi’ betrays its origin, the mountains of south west China, where Father Jean-Marie Delavay went to convert the heathen and became one of the most industrious plant collectors, with 1500 new species in his bag. ‘Meadow rue’ is the English name for the family; the finely divided leaves, in this case palely glaucous and scarcely significant in the picture, explain the name. The monster hybrd ‘Elin’ proves that bigger is not necessarily better, and the double one, ‘Hewitt’s Double’, that two is not necessarily a higher value than one. Of all the perennials I grow in our perpetual shade this is the most striking and rewarding.