Nature, said Galileo, cannot grow a tree or construct an animal beyond a certain size, while retaining the proportions and employing the materials which suffice in the case of a smaller stucture. The thing will fall to pieces of its own weight…….. become clumsy, monstrous and inefficient, unless we change its relative proportions, or else find new materials….

No, I wasn’t reading Galileo in the original, I’m afraid. I was reading him in D’Arcy Thompson’s great book On Growth and Form. D’Arcy Thompson? He was a giant Scotsman. physically and intellectually, a classicist, mathematician and Professor of Biology at Dundee University for no less than 64 years. On Growth and Form was described by Sir Peter Medawar as ‘beyond comparison the finest work of literature in all the annals of science..in..English’. I read it when I was writing my tree book 35 years ago. Now, preparing a new edition, I am reading it again.

Thompson’s originality was to consider evolution in terms of physics and mathematics. Why do things take the shapes they do, and grow to their proper sizes? What is a proper size? Trees and their growth apart, we seem convinced that growth is esssential to the success of any organism. Why does a business have to grow? To stay ahead of competitors, to profit by economies of scale, to fulfil Mr Micawber’s definition of happiness… or just because we equate growth with success?

Reading Thompson, strangely enough, made me think about the RHS. It started life as a learned Society, kept going in more or less the same spirit for ovr 150 years, then in the past decade or so put on a furious spurt of growth. It is the demotic spirit of the age. Perhaps it is essential for survival. Perhaps it will, in Galileo’s words, succeed by changing its relative proportions or finding new materials.

I concur, of course, with those who hold it is dangerous and immoral to muddy the pure waters of taxonomy. To give, for example, an unauthorized name, for whatever reason, to any plant that has a good (or at least a valid) name already. Synonymy, with names that are merely hort adding to the complication of those that are bot, gives the compilers of The Plantfinder half their problems. Ignorance is the only possible plea.

And yet…. Frail gardeners sometimes know only one thing for certain about a plant – who gave it to them. Its genus, probably. Its species, perhaps. Its variety or cultivar name, more foggy. I’ll confess. I grow a hydrangea that I have never matched with an official name. It is a ravishing tender blue pale blue with no electricity in it and fades into shades of lavender and grey and green. I am probably put off the scent by our soil conditions; my interest, frankly, is simply in keeping it as it was when I was given it, by a dear friend and veteran (among many things) gardener, now 90, called Leonard Ratcliff.

Guess what I call it. It’s unauthorized, immoral and the rest, but in this garden Leonard Ratcliff is its name, and who knows it if may be passed on with no more official label.

I have a proposal to make the situation plain. Heaven knows there is enough in the rules already about capital letters and inverted commas. But I add another rule. I am using the > and < symbols before and after it. It is both more than and less than the name I know it by. If I call it Hydrangea >Leonard Ratcliff< that should be reasonably clear.

After the study day at Kew in the spring I was full of resolve to give my trees a thorough Kew-style mulch of woodchips. Spring-time surgery had given me substantial piles here and there in the garden. It was a shock, then, to discover, when I started to move one, that it was solid – literally stuck together – with the bootlaces of honey fungus.

Wisley soon confirmed that this is indeed Armillaria – A. gallica rather than the cruelest species, A. mellea – but definitely not something you want to spread round as mulch. ‘Compost it to 50° C’, they said. I’m afraid the bonfire is where it will go. But be warned: woodchips may not be as innocent as they seem.

I’m always baffled by dew and its effect on plants. It comes, of course, on clear and relatively cold nights, recently almost every night – which is odd because, though the sky has been a sea of stars, the temperature has not dropped as you would expect.

There is nothing mysterious about the process: the ground surface radiates its stored heat into the atmosphere, making it colder than the moisture-laden air, which condenses in drops – especially on grass. The quantities are not large, the equivalent of perhaps half a millimetre of rain at most. In drought conditions, though, when plants are under serious stress, it makes a difference.

The difference appears greatest where sunshine doesn’t evaporate it next day. There are patches of shade in this garden now where the grass has started to grow quite strongly, lush and damp all day. Paradoxically these are places that remain covered from the clear sky at night, where the dew falls must be less. Evaporation therefore seems more important in the equation than precipitation.

On the North Kent Downs where I was brought up dewponds were common. They consisted of shallow hollows perhaps 20 feet across and four or five deep, lined with flints, handsomely built and apparently ancient. They seemed to hold more fallen leaves than water. Apparently they were lined first with clay, then with a thick layer of straw, then with chalk, crushed fine and rolled to a smooth surface, before the flints were applied to protect it. The principle was to insulate the pond from the ground beneath and its radiation of heat; to make it a cool dish to attract condensation on clear nights. But a shower of rain, I’m sure, was even more welcome.

‘When they’ve finished the duckpond, can they have the moat?’ said the voice on the telephone at midnight. I recognized the voice: a neighbouring farmer’s. ‘Haven’t you heard?’ (the standard Essex formula for breaking news) ‘the coachhouse is on fire.’ The coachhouse is 400 yards away at the other end of the village. By this time I had opened a curtain to look towards the duckpond. It was invisible for flashing blue lights. We pulled on clothes and dashed out. There were three fire engines drawn up by the water, their engines throbbing, and a tangle of fat hoses leading out of the gates and down the street. The sky at the far end was brilliant orange and full of sparks.

When we reached the coach house the roof had fallen in and waves of pale flame were attacking the gables. Five more fire engines were throwing water at it. A man on a tall ladder held the hose from the village mains supply, issuing an ineffectual dribble. The duckpond was providing full jets from the other hoses.

An hour later the flames were under control and we went back to see fish floundering, as we expected, on the bottom of an empty pond. The level was down perhaps two feet, but there was a little way to go. The moat, happily, had not been needed at all.

Why am I recalling this now? (It happened in April). Because now, after a dry summer, the duckpond is lower than we have seen it in 40 years. You can walk to the island. When you empty a long-standing reservoir (and this has been here for centuries) can you be sure it will ever fill up again?

What is the absolute minimum that can constitute a totally satisfying garden? I found an answer last week in that paradisiacal part of France they call La Provence Verte, a region of pines and vines at an altitude that gives cold nights summer-long, very different from the sun-baked grey-brown garrigues of the country round.

We were staying with friends in one of those tall, almost urban-looking chateaux of the early nineteenth century, classical, well-proportioned, unornamented and a touch severe. The walls are a pale ochre, the shutters blue-grey. The garden is on two levels; that of the house and, linked to it by two stone staircases curving symmetrically round an oval bassin, a lower terrace, a simple lawn. Both terraces are surrounded by stone balustrades.

The upper terrace, the space in front of the house, is a plain unbroken expanse of that almost dust-fine gravel we don’t seem to know in England – but then we don’t play boules. It is shaded by four towering plane trees and one lime. The lawn below has four more planes, contemporary, I dare say, with the house.

The only flowers are red geraniums in tall oil jars in a row across the façade. Does the gravel sound anticlimactic? It is serene. Gardening consists of keeping it clean, dragging a sort of harrow consisting of chains over it, to efface the marks made by the boule-players. The play of light and shade do the rest.

Moaning about drought doesn’t get you anywhere, especially among friends who have just spent two weeks on Mull without a single dry hour. With 360 millimetres in the pot, moreover, we have had a fair proportion of our expected 500 mm annual allowance. So why are my arms so long from carrying cans, and why are my recent plantations so desperate for a drink?

Most of the rain fell, it is true, last winter and in July. The longest sequence of rainless days was in June and August, when the other side of the island was being soaked, but never more than 12 days or so without some dampening shower. The truth is that watering individual plants is never a substitute for

a good hou of rain. Even putting the rainmaker on is a pis aller. I suppose the reason is that competition among the congregation of roots that fills the soil. It is easy to think of plants that you can pull up with a neat tuft – but they are the minority.

Most plants insinuate their roots into as much ground as they can, whether others are occupying it or not. My can of water is the invitation to beat up the poor new boy in the class.

Is this the reason my salvias have been so slow to perform – the ones I scrounged in Scotland last summer? We paid a call to Powys Castle last weekend to see Wales’s great window-box at its most floriferous. Powys is famous for overflowing pots and vases of tender things in daring combinations, and by September all its hanging terraces, stacked below the red stone castle, bubble and froth with exotica. I drooled over it all – but especially over the salvias, in varieties I had never dreamed of, pouring down, rearing up, infiltrating their neighbours with their predictable but still somehow surprising pouty flowers in every colour from scarlet to searing blue to black and
green.

What did I do wrong? By the time mine are flowering in earnest the frost will be getting them – or even, fingers crossed, serious rain.

It is tempting to take credit for the happy accidents of gardening, to pretend that you planned a chromatic chord due solely to the almighty or (as is happening just now) the look of airy intricacy in borders buffeted by the wind.

It takes a lot to reconcile me to wind in the garden. Out in the fields I love to watch the straining grass-heads and the tossing trees. A line of Browning’s came to me just now as I climbed from the sheltered streamside out on to what passes in Essex for downland: ‘an everlasting wash of air’. Browning was in the Roman campagna where the grasses and rushes wave mile after level mile.

The border looks airy partly because I have taken the shears to tired plants with more resolution than usual, hoping for a second coming of delphiniums, thalictrums, campanulas, geraniums, valerian, even phlox. September flowers, as a result, are clear of clutter. My favourite of the moment is a clump of Francoa ’Bridal Wreath’, its white wands of flowers rising from its solid saxifrage basal clumps. Last winter nearly put paid to it; it struggled in spring, and as a result is late enough in flower to mingle with the lovely bright blue Salvia ‘Guanajato’ that is just getting into its stride. Is my Francoa sonchifolia, the default species in Graham Thomas? I think not: the flowers are pure white with none of the red spots G.S.T. mentions. Almost certainly F. ramosa.

Margaret Waterfield (am I her last fan?) in her book Flower Grouping in English, Scotch & Irish Gardens (no publisher would call a book that today) painted a group of F. ramosa with Dierama (then Sparaxis) pulcherrinia, an image that haunts me with its beauty, but I have never achieved. She says, surprisingly, that the Francoa is hardier than the Sparaxis. Watercolours like hers (the book was published in 1907, by J.M. Dent) are an almost-forgotten treasure, conveying airy intricacy, or any other happy effect, more precisely and evocatively than photography has ever done.