Two ‘pencil’ cypresses of my acquaintance have just died, quite suddenly – and they were both strapping young trees; the bigger one a good 20 feet high. One was my sister’s, a 10-footer, rather shaded by a magnolia but looking fine in the spring. She reports ‘caterpillars’; I see no sign of damage. The other, three gardens away, has the equivalent of the Plague’s black boils, the fatal mark of a brown stain spreading up one side. It looks exactly like the phytophthera that carried off our Irish juniper alley, all forty of them, one by one, at Saling Hall.

Naturally I gave my own small cypress (another 10-footer) a close going-over. There were brown needles here and there, and a lot of the small inner branches were dry, but there is no sign of pest or disease, While I was up the ladder I snipped out all the brown material. A lot of brown needles (not an accurate description, but leaves is hardly the right word either) were snagged in the branch

forks and clinging to the trunk. Thoroughly snipped and brushed down the tree looks a trifle sparse, but I shall be able to spot any sign of trouble straight away. Whether there is anything I can do about it is another matter.

It’s not so easy with box hedges – or any box, come to that. We and all our neighbours are on high alert for the boxtree caterpillar which eats the leaves and can denude a bush in a few days. He is tiny, with a dark green and yellow body and a black head; the yellow part is what to look out for; he is a demon at concealment. We were only away for a week last August when he attacked; already he had spun tiny webs al over the hedge and eaten the leaves inside. Now it’s a daily inspection, with Pyrethrum (sold as Py) at the ready.

You hear of gardeners panicked by the mere threat, and rooting out their hedges (as Roy Strong did at The Laskett at the onset of box blight). It would be tempting if there were a box substitute; in reality the Ilex crenata, the little berberis and hebe that nurseries propose, let alone the santolina or lavender I see suggested, can only remind us of the timelessness of box. A box wipe-out would be an international catastrophe. I think of great formal parterres and shudder. But we can dwell too much on threats. If every stag-headed oak is a premonition and we start at a dead branch in an ash the risk is that we stop enjoying all the glorious growth around us. Be watchful; be forearmed.

Top: the Cascade des Planches, and below it Stourhead

It’s the sound of God washing his world. Gently rinsing it, rather, with a night of unemphatic rain. I am out on the verandah at midnight, mingling the scents of orange blossom and Pauillac, my bedtime glass. The rain is a cocoon, soothing away all other sounds. Time to reflect on a month away on visits to gardens, houses, churches and the seaside. A dry month, at times too hot; hence the luxury of this healing rain.

My iphone has become my chief remembrancer; shameful to admit, but the snaps in its camera are my garden notebook; more than that; almost my diary. What’s more it knows where and when I took them.

It tells me that in the past month I’ve been to the Loire, Burgundy, Arbois in the Jura, Champagne, Kew, Suffolk, Exbury, Dorset and Stourhead.. The photographs recall people, plants, places…but in that fatally selective way that (if you’re not careful) screens out more complete memory. It’s an obvious trap. We laugh at Orientals and their selfies in front of iconic views: endless smiles; how many memories?

There are, of course, occasions when photography becomes the main object. Then I will circle round an object, or investigate a garden or a building, for hours in the hope of a telling angle and the right light. The camera fills up (only it never seems to) with alternative shots that are impossible to edit properly on its tiny screen, and are usually disappointing downloaded at home. Choosing the best shots of a sustained session takes longer than the shoot itself.

My favourites from July? A wonderful waterfall we found near Arbois on the river Planches, where a cascade crashes out of a forest to form a staircase of pools and line them with marble-like tufa. An octogenarian topiarist in Burgundy carving yew piéces montées in blazing sunshine, a cave of ancient wine bottles belonging to an avant-garde sculptor at Jasnières on the Loir. Then our old garden and woods in the Auvergne, a German military cemetery in Normandy with a thousand mophead maples in parade order in the rain, a girl in a restaurant in the Jura, the magnificently austere cathedral of Laon in Champagne, isolated on its hilltop, and back in England, sailing down the Beaulieu River past Exbury gardens, Christchurch Priory and Sherborne Abbey for glorious medieval vaults, Stourhead for its lake and its magnificent tulip trees. You can travel a long way and see no finer sight than Stourhead.

Tulbaghia violacea, Cap Ferrat, and a chance of rain

We (the collective we) go south in summer for sun because we can’t be sure of it in England. It’s a taste our grandfathers would have found puzzling. They went south, if they could afford it, in winter and spring. There was and is lots to do at home in summer, and frankly not a lot in the overheated summers of Provence or the Côte d’ Azur beside splashing about in the tepid sea.

I am on the gorgeous Blue Coast now. It’s too hot to be outside, except in the pool. Air-conditioning is as disagreeable here as anywhere else. Shade and a breeze is the sum of my desires. And eye-soothing green is not to be found. It hasn’t rained, I’m told, for three months. The grapes hanging on the pergola are shrivelled but not ripe or sweet.

Admittedly the Iceberg roses are splendid, but there is little else in the garden to admire. I’ve often puzzled about the iciest roses lapping up the hottest weather. The rather lanky solanum bush (S laciniatum, I’m pretty sure) with purple flowers the size of your thumbnail is worth seeing – but so it is in London; a cutting from this very plant. Indeed my plant palette seems to have got a bit bogged down with duplicates in Beaulieu sur Mer and London W8. Japanese anemones, and the Tulbaghia in front of me now, little umbels of pale pink flowers on long stalks over a chive-like clump of leaves, waving at horizon level over the blue of the bay, Pale Perowskia is not happy in our London shade, and here the hydrangeas were over weeks ago.

What are we left with? Lavender, lemons, apples, persimmons (not in London). No bougainvillea in London, either; luckily I don’t much care for it. Plumbago, though, I would certainly try if I had a sunny south wall. There are one or two salvias that come close to its pale sky blue, but nothing on its scale.

Agapanthus 'Northern Star' . More purple than blue in this photo, but a glorious colour.

To Kew to see how the mammoth new herbaceous borders are coming on. When they were inaugurated in April, after a year or so of preparation, they still looked enigmatic.. Three months has been enough to turn promise into spectacular performance: surely one of the horticultural wonders of the world. The two borders together total over 2,000 feet of planting; I heard someone mention 30,000 plants. The scale of the project and its ambition, to make an immense tapestry of interwoven plants, of well-considered colours, without hesitation, deviation or repetition, is almost Victorian. Follow the planting schemes carefully and you can see how conditions change with the influence of the other plants around. At the Palm House end there are big trees closing in; the choice of plants tends towards the woodland. It will be fascinating to see how the components knit together and form new patterns of colour. What a job taking care of it will be for some lucky gardeners.

The sight of the Broad Walk disappearing into the distance, thronged with families and lined on both sides with splendid planting, makes me think of the Great Exhibition, the Crystal Palace and the confident achievements of Victoria and Albert. For sideshow there is The Hive, the new pavilion promoting the work of bees in fertilizing (among other things) 80% 0f our food plants. The Hive is a rather beautiful structure formed of aluminium struts, suggesting the complexity of a beehive – and buzzing and throbbing with the amplified sounds of the bees in Kew’s actual beehive nearby.

In the first really warm days of summer, after more than generous rainfall, Kew was looking wonderful. It is Lime Time (Tilia Time to botanists) when the air is sweetly dense with scent from millions of flowers decking some of the biggest trees.

It’s pretty good in the garden at home, too – all 900 square feet of it. The warmth has brought plants into full flower that have been looking tentative, in some cases for weeks. It has pressed the release button on reluctant roses. Salvias and agapanthus are loving it. I am always on the lookout for blue flowers. I home in on them in every garden I visit and in every nursery. There is a (short) book to be written about their allure – and relative rarity. Salvias and agapanthus provide some of the best. Each summer I keep my fingers crossed for Salvia patens to reemerge, and this year I was delighted to see S. vitifolia (big furry vine-shaped leaves and caerulean flowers) had survived the wet winter. We came back from France with a new agapanthus acquaintance: the positively sapphire Northern Star which a friend had planted in big pots, repeated forty times around the terrace of their 18th century hunting lodge, each, with the sun behind it, a gleaming gem. We modern gardeners don’t know how spoilt we are; our ancestors had nothing like this.

Can there be a greater satisfaction in gardening – or in life itself, for that matter – than seeing your careful plans coming to fruition? It is ten years since we sold our place in La France Profonde. Veteran readers of Trad may remember my probably obsessive accounts of tree-planting, building and garden-making in the wide open spaces of the Bourbonnais, the northernmost part of the Auvergne. Bocage (as in Normandy) is the term for the repetition of field and copse and wood and hedgerow that makes such soothing and satisfying prospects.

The vast green rug of the Forêt de Troncais, 25,000 acres of tall oaks, the best destined for wine barrels, dominates the region. Our little farm lies in its pastoral fringes. Charolais cattle, bulky and pale, are the main signs of life around the red-roofed farms.

Our successors have kept everything going as we planned it – even our ancient Land Rover. We bumped around the familiar tracks, looking up at trees I remember as little saplings. Pines we planted in 1994 have had their first thinning and now look like grown-up forest. Oaks that seemed so reluctant to grow at first (and needed expensive protection from the deer) are now an impenetrable green wall, house-high. Better still our successors keep the network of rides open and mown for their horses; perspectives that were lines on the ground are now gloriously three-dimensional; the shape we gave the landscape in our imaginations is a reality of masses and spaces, shapes and textures, with a logic that reveals itself as you move.

In the only spot where the gritty acid soil is deep enough, with enough moisture, I planted half an acre of American oaks and maples to fire up in autumn. Sugar maple and swamp, scarlet and willow oak are trees I could only dream about at home. Here in acid soil and a continental climate (it was 35′ C when we were there) they far outgrow the native species.

And the parterre we squeezed in an awkward sloping trapezoid space between house and barn has acquired authority; you can’t imagine the enclosure filled in any other way than with its beds of box, its walls of hornbeam, troughs of hydrangeas and a froth of blue and white flowers. Only the vineyard has gone, to make a paddock. They were right: the wine was never going to be great.

All summer long

I wish I had kept count of the number of plants that were considered exotic, or treated as tender, when I started gardening, and are now seen as mainstream. I remember, for example, planting my first agapanthus. It must have been about 1972. I waited until June, dug a hole in the sunniest and driest spot, buried crocs and gravel, and tenderly tucked them in. “Headbourne Hybrids” were supposedly the only strain with a good chance. In October I covered them with slates on bricks to keep off the winter rains. They are still flowering, as far as I know, forty five years later.

Is it acclimatisation, breeding, know-how or climate change? Possibly all these things. London, of course has been practically sub-tropical for years now. Remember how we once marvelled at the old olive tree in the Chelsea Physic garden? Now blue and white agapanthus (‘Blue Storm’and ‘White Storm’) line a wall in this Kensington garden, shaded for most of the day, and flower well, if not lavishly. The trick, I find, is to be generous with water and a high-potash feed in spring and summer. Our best plant is ‘Northern Star’; tight-filling the same large pot for five years; it has six tall stems on the point of flowering. I keep its saucer half-full all the time. This year’s new treat is a variety called “Queen Mum” I bought from Hoyland Nurseries from Yorkshire at the Chelsea Flower Show. The flowers on long stems are white, but each petal starts off blue; more of a specimen for a pot, I think, than a border.

Trachelospermum jasminoides (‘Star Jasmine’) was thought doubtfully hardy until quite recently. Now smart London is full of it, and last year we discovered Jasminum polyanthum, which doesn’t seem even to have an English name yet, has moved convincingly outdoors. Fuchsias in the open no longer surprise us. London-centric I may be, but how many things have you found can dispense with customary winter protection?

Shellwork at Ballymaloe

Would you like a grotto? Do you warm to the idea of a cool shell-lined cave, water dripping from stalactites, mysterious reflections in a dark pool? They’re back in fashion. I went to what must be the most beautiful grotto of modern times at the Ballymaloe Cooking School near Cork, a crustacean mosaic, a pristine masterpiece of a summerhouse (no water, admittedly) that perfectly expressed the spirit of what? Grotteity? Grottiness?

Last year’s winner of the PJ Redouté Prize for the best garden book* in French is a tombstone of a volume on grottoes, illustrating a score of magnificent creations, some glistening bright, some spooky, all cool retreats from the sunlit world. It classifies them as, for example, Primordial, Diluvian, Labyrinthine, Sacred, Tellurique, Profane, Underworldly – and the Introductory chapter is called Ouvrir L’Ombre – opening the shade.

As it happens, we have a grotto of our own, deep in the Welsh woods; a rocky tunnel a hundred yards long that set out to be a goldmine but drew a blank. Its mouth, protected by an iron gate, is a gloomy hole overhung by ferns and issuing a dark and gleaming stream. Penetrate the depths (take a torch) and you are in a world of black, dripping rock, with here and there a little cascade to cool your collar.

The grotto spirit, though, can be expressed in less ambitious ways. I have been looking round this tiny garden for a corner to transform into an alcove plastered with shells, with perhaps a pretty dribble into a basin. For now we just have a tank with a Mr Spit like a Green Man and four goldfish; two tiddlers and two gorgeous ‘comets’ with wide waving tails called Halley and Haley (Bopp).

*The book is ‘L’Imaginaire des Grottes dans les Jardins Européens’by Herve Brunon and Monique Mosser. Oh yes; moss. Another essential.

A busy evening after an Ascot downpour (the Queen Anne Cup, I believe: I stayed at home) emptying brimming saucers and relocating snails. Where do they live, waiting for Ascot week? There were fifteen in one corner enjoying the shelter of the agapanthus. Total score for the evening: twenty seven. And why do they climb? I’ve found senior snails climbing down from ten feet or so on a wall. Do they want a better view?

The slugs have meanwhile climbed a newly-planted Clematis wilsonii (a treasure from Hergest Croft) and munched its top shoots before disappearing – presumably to destroy the little Eccremocarpus scaber I planted to keep it company. How this unobtrusive climber came to be called ‘Glory Flower’ I can’t imagine. Its little red and yellow bells on the flimsiest rigging deserve ‘charming’, but certainly don’t compare with Morning Glory. The strain I have (or had) has modest pale creamy-yellow flowers, all the more welcome for unexpected cameo appearances among more socially confident blooms.

I tend to think Chilean plants should be rainproof, but E. scaber likes it dry. So does the marvellous Abutilon vitifolium (American name: Flowering Maple!). Its tissue-weight petals, rather on the hollyhock model, in either lavender or pure white, look as though a shower would destroy them, yet I have seen them in rain forest growing with luxuriant Eucryphia and Weinmannia as dense as redwoods.

A wet Ascot makes a good growing season. Just-planted specimens can grow on without check; established ones, even big trees whose hydrology you would think had settled into a pattern a century ago, can react with a surge of lusty shoots the very next day. You think a tree or shrub (or indeed a perennial) has done its spring thing. Then another downpour and away it goes again, the new wood barely able to support the new new wood.

You can see the effect of rain on growth rates, but what about temperature? It has gone down to below 10 degrees C, ‘growing temperature’, several nights recently – and not got much above all day. Clearly the average temperature is enough to keep things going, but I’m sure when there were two days of sunshine I saw them put on a spurt. I’d love to understand the sensitive mechanism that tells cells what to do.

There’ll be a lot of hacking back to do to keep the paths open this summer.