I may well lose more readers through my enthusiasm for weeding, annually expressed, than by being boring, repetitive, out of touch, living in the past and my many other weaknesses. I can’t help it. Weeding for me is the epitome of gardening; the time when every move is decisive and, to use that corny phrase, you can see where you’ve been. Planting is the other supreme gardening pleasure; the satisfaction of settling roots in soil always gives me a glow. But planting is the work of moments, while weeding is a long drawn out pleasure, always (at least in this garden) available.

Why do I love it? Because it calls for total concentration. As I stoop or grovel in the border (or anywhere else where muddle is taking over) my eyes must be fully focussed. What appears at first an agreeable jumble of green shapes becomes progressively clearer as I start to edit it. There are in-your-face weeds: a dock or a nettle makes no attempt to hide. There are insidious weeds that blend with the background: violas and little balsams that can lurk while they multiply. And there are wily, snaky weeds that infiltrate under disguise.

Just now it was bryony in a mahonia that had reached the top without my noticing. Always and everywhere it is goose grass, spreading out from a root no bigger than fuse-wire to launch its sticky tentacles into whatever it encounters. It took me five minutes of patient groping, using its rough texture on my fingers as a guide, to disentangle one plant of it from a patch of Geranium.

I have learnt a few tricks, leaning over the herbage, breathing in its evocative  variety of smells. The first is always to use a fork – not always to prong with, but more importantly to lean and balance on. It’s the rule of ‘one hand for the ship’: right hand on the handle for balance, left hand for reaching down and out. You can reach improbably far into a border if you are a tripod.

There are plants that never seem to need weeding, but they are rare. I rarely find weeds in established clumps of hemerocallis, and the big leaves of Phlomis russelliana are exceptionally effective at covering the ground. Some geraniums are hard for casual weeds to penetrate, but nothing, of course, smothers bindweed. Nor I fear is there any pleasure in it. In fact, I exclude bindweed, couch grass and ground elder from my enthusiasm. So perhaps I am not so different from other gardeners after all.

The camera zoomed in from an improbable height above the royal Bentley purring back from St Paul’s. On the way it encountered the branches of a plane tree and saw right through them, through sadly deleted leaves and sagging shoots, in a way you never can through the canopy of a healthy tree. London’s planes are sick, some of them very sick, and the prospect of their decline is too dreadful to contemplate.

Is it a new disease, as some suggest, or the occasional weakness that strikes them under peculiar circumstances ? Does it relate to a hot dry early spring followed by a long cold and wet April and most of May – and June? I used to worry about an alley of London planes I planted in central France; in some years, particularly in wet springs,  their new shoots died back as we see them doing in London now, but 20 years on they are robust young trees.

Central London has been verging on a monoculture of planes since its elms died nearly forty years ago. We forget how important they were. Many of the finest trees in Hyde Park, for instance, were field elms, with their crowning fans of branches, their flaring skirts and their pale gold leaves almost to the end of the year. London has few oaks and not nearly enough limes. The resilience of the plane, it resistance to pollution as well as its majestically graceful canopy and its huge reptilian trunk, have given it the status of the London tree.

The local authorities have been imaginative in the past few years with their street trees. We see rowans and alders, ginkgos here and there, many hawthorns in the parks, and so many Chanticleer pears that we have to hope they are resilient too.

But the mainstay of our parks and squares is the London plane. Since the 18th century it has defined the landscape of the West End, historically and practically. It is strange that a sterile hybrid should become the climax tree of the London forest – and should certainly be worrying us now. We desperately need to find a treatment to keep them going.

I remember my moment of disillusion. It was in Berkeley Square. An enormous shiny car came round the corner of Bruton Street pretending to be a Rolls Royce, but instead of the familiar silver Parthenon and its floating goddess its radiator was like the front of an American truck: a bloated travesty of a classic design.

The whole vehicle was gross; engineering grace had given way to gigantism. (I heard to my delight that the makers had to reduce the length of the thing for Hong Kong to avoid it being classed as a lorry).

The same feeling of revulsion hit me again in my favourite London space, the Green Park, the other day when the wraps started to come off the new memorial to Bomber Command. It looks as though someone was using someone else’s credit card in the

Haddonstone catalogue: a hundred yards or so of pseudo-classical columns supporting a useless architrave. In the centre will be a bronze group of the heroes it celebrates.  Apart from the question of waiting 60 years to mark a tragic victory over a country now an ally, why do we need the exceptional emphasis of this giant colonnade?

The western gateway to London, Hyde Park Corner (Apsley House was once known as no. 1, London) has become a showroom for ever-bigger memorials. Where once a single statue represented a hero and sufficed for a regiment, we now seem to need a quarter of an acre of masonry. The New Zealand memorial just across the road has sixteen black exclamation marks where one would have been eloquent and dignified. The Commonwealth Memorial Gate awkwardly straddles Constitution Hill with undistinguished masonry, like a pedestrian crossing with an inflated ego. Anywhere in Monument Alley, which now encompasses Park Lane as well, seems fair game for this new branch of the building trade.

You can cite the Albert Memorial, of course, as pretty extravagant. But where are we heading, with the idea that bigger is better? Think of the Mini, and shudder.

This is the time of year when they have to send out a search party for me as the light fades and it’s time to decant the claret.

It’s the time of overload anyway, when too much is happening at once. What is a coherent reaction when nineteen plants are calling out to be admired and ground elder is flowering lustily in their midst? This year there is confusion to add to surfeit. Why is

the banksian rose in full flower at the end of May instead of April? Has Magnolia soulangeana finished flowering or not? And why not? Camassias overtook bluebells, weigelas overtook azaleas, ashes are still bare and hawthorns are still opening an unprecedented froth all through the hedges.

This is when I realize how over-full the garden is, how tall the trees are and how jam-packed. An arboretum has become a forest while my back was turned – except that it wasn’t: I’ve been staring at it in ecstatic indecision spring after spring, thinking how lucky I am.

Rhododendron augustinii

To Bowood on a rainy day to visit the Rhododendron Walks, open for the first time this year. It is almost incredible that England still has such wonders under wraps, but the Lansdownes have kept this separate part of the gardens, miles across the estate from their celebrated Capability Brown lake and spectacular water gardens, as a private enclave around the Robert Adam family mausoleum.

Why miles away? Like many rhododendron collections it relies on greensand, ridges of which crop up on high ground, principally in Kent and Sussex but also in a line between Poole harbour and the Wash. At St Clere in Kent, for example, the Pinetum perches remotely and incongruously on top of the North Downs; beech hangers below, conifers and rhododendrons on top.

At Bowood the woodland garden is sheltered and framed by oaks, and some of the most venerable beeches I have ever seen, on a series of steep spring fed slopes that offer everything rhododendrons could need: shelter, moisture and air-drainage.

Some of the first collections from the Himalayas were planted here in the days of Sir Joseph Hooker, by the great great grandfather of the present marquess. Subsequent Lansdownes have added to what is now a woodland garden of extraordinary beauty, while the present marquess, the eighth, is a full-time hands-on gardener. I am no rhododendron expert, and easily impressed by a bush thirty feet high covered in huge pale pink flowers giving off sweet scents. When I am told that it is one of the earliest hardy hybrids with Himalayan blood, and that its name is lost in time, I can only nod in assent. It is clear why such creations became the show-flowers of the great, raised and selected with as much care as their race-horses.

Satiety would soon be reached, though, if they were too densely planted. It is the beauty of Bowood that there is space and variety, that glades and rides, pools of bluebells and grass open to the sky make it a magic wood rather than a rhododendron forest, There is the delicacy of white dogwoods, the brilliance of Pieris, one the size of a cottage, and above all, here and there among the rich green and the pale glades, floating over the bluebells, the sumptuous near blues and purples of Rhododendron augustinii.

If I were to have one rhododendron it would be this native of Sichuan, the nearest flowers to blue produced by its tribe. In fact it is the only species I have planted in our North Welsh woods. (R. ponticum needs no planting). Ten years or so ago I planted a dozen plants around a waterfall and along a stream under beech and larch. Accidents happen in a forest; sheep the most frequent. Eight of my augustiniis survive, now ten feet high, their feet in bluebells. Why didn’t I plant fifty?

The rain at Bowood, at least in retrospect, was like the creative touch of a great director. The shine and drip (it didn’t pour), the grey light and the cool soft air completed the magic and made the exotic (even the ultra-exotic) seem believable.

Bluebells at Bowood

Plain simple degrees, and lots of them, are what the garden needs this miserable May. Fahrenheit or Celsius; it won’t mind.

The plants are in as much of a muddle as I am, not so much early or late as all over the place and not going anywhere. Oak has never been so far before ash, but magnolias are just sitting, their flowers half open, some petals frosted, others effectively drowned. And my favourite winter-flowering cherry has caught that nasty fungus and lost all its leaves.

By early April we had had a mere 140 millimetres of rain in the year. Since then we have had 160. If it was the wettest April it is the coldest May. The only plants that keep on growing in this low temperature are weeds and grass; the mower sinks in to the boggy ground and any step on the border to reach the weeds leaves a foot-shaped puddle.

And yet. When I splashed out this morning in my winter coat to see what could be done I walked into a wall of what to me is the Chelsea smell: azaleas in all their boudoir sweetness. The pale faces of Azalea mollis, soft yellow in the grey light, were gently chiding me: look at us, you grumpy old fool.

A reverie is a comfortable place to be. I have just spent ten, fifteen, I’m not sure how many minutes watching Berberis petals float over a weir: tiny flakes of gold on black water, drifting slowly, with a growing sense of purpose, over the surface of my little rock-rimmed pond.

The weir (the whole thing is tiny: the weir three inches across) acts like a magnet, mysteriously setting the surface in motion. Petals settled in the centre of the pool begin almost imperceptibly to move, gradually, gently organizing themselves to head towards the fall. Little groups of four or five move together, as though some force (could it be surface tension?) held them in formation. Individuals feel the same pull and move at the same speed.

I switch focus and look deeper, through clear water to snail trails (if that’s what they are); paler tracks on the leaf-littered bottom. It has always baffled me how we can switch our vision from reflections to the surface, and through the surface to what lies below, with only a change of thought.

Three feet from the weir the petals change course, reset their sails and pick up speed. They keep in their flotillas, but now there is urgency in their drift, they collide, form bigger squadrons, then coalesce into a pool of gold to hurry through the gap between the rocks. They fall perhaps an inch, perhaps two, but just enough to break the surface into silver glints.

As a way of seeing the whole world it is much more interesting than a grain of sand.

I honestly didn’t plan the look of the garden now. I would never have been so bold or single-minded, or trusted to the impact of a single flower. It is a triumph of the Triumphator. Who named this simple white lily-flowered tulip I don’t know. Perhaps he or she had the same experience. The long files of bulbs I planted three or four years ago down the centre path of the garden have the stage to themselves, shining white, ice-cool on a background of tender greens, sharp green, and the bottle-bank brown/green of box hedges.

Why are there no other colours? Two weeks of constant rain seem to have left most plants perplexed. The Crown Imperials have finished; one or two tentative flowers sprinkle little pink geraniums and a burgeoning perennial honesty. The apple trees are in blossom, but the colour seems washed from their petals: there is no wattage in any colour except green – and the bright lamps of White Triumphator, its pointed petals upright despite the downpours.

If it is true, as Christopher Lloyd feared, that this marvellous bulb is growing degenerate, and that its stock is weakening, it would be a terrible shame. It is seventy years old, I learn – though I still don’t know who coined its strange name. But if this is weakness; three years in the ground and still standing straight after two weeks of rain; triumphator, meaning hero of a Roman ‘triumph’, is right.