One person says La Mortola is on the way up; the next visitor says it’s worse than ever. It’s been like this since the 1980s, when a posse of busy-bodies, largely from the RHS, (I was one, but the one that counted was the much- admired Director of Wisley, Chris Brickell) took action. The staff at this famous garden, the creation of the same Hanbury family that gave the RHS the land for Wisley, had gone on strike. The Hanburys had sold the property to the Italian state, little thinking what a mess Italian bureaucracy can make. What had been one of the world’s best sub-tropical gardens, a superb botanical collection on the borders of Italy and France, at the very point where the Alps collapse into the sea, so steep and sea-surrounded that frost never comes, was a weedy chaos, under soaring palms and cypresses and far rarer trees.

On my first visit the striking gardeners were camping in a cave-mouth near the monumental entrance. Negotiations followed, with British botanists setting new standards for organisation and maintenance: eventually the University of Genoa took responsibility. The question is, how are they doing?

The other day I was pleasantly surprised. The garden covers 18 hectares. You can’t expect perfection. But the most exceptional parts, collections of succulents and cycads in particular, are well weeded, cultivated and surprisingly well labeled. The whole garden looks in good health – even the lower reaches towards the sea where the citrus orchard is crisscrossed with pergolas. There are areas of long grass and weeds, but no dereliction.

There was one black moment, though: the discovery of a new (to me) and horrific predator on the box plants. It is a moth (Cydalima perspectalis) and its yellow, black-spotted caterpillar which gobbles box leaves and shoots until the plant is bare. “Piralide” is its vernacular name. It arrived in Europe three or four years ago, in Italy last year, and has (as you have guessed) no authorized treatment. One French gardener I know has gone on a spraying course to be ready for action, but the red flag is hoisted. What will it make of our island’s weather, and miles and miles of box hedges, I wonder.

Just home from the afternoon at Kew, to see the beautifully staged orchid show. Where do they hide these magical creatures the rest of the time? Marshalling such feats of cultivation to dramatize their story is a brilliant idea: crowd-pulling, absorbing….. a triumph. Even without the orchids, though, it would have been with the journey to see the seas of humble crocuses jostling in the wind.

The little ‘Tommy’, Crocus tommasimianus, beats the snowdrop in charm, simplicity – and in coming first. This year, in fact, even before the snowdrops have woven their carpet. I’m not sure how, or even why, its varieties (Whitewell Purple, Barr’s Purple…) are distinguished. Infinite nuances of colour are the attraction of the crowd.

Are the individuals different, and does it matter, when the tops and bottoms of their petals, darker and lighter, mauve and silver, are rippling semaphores across the grass?

Even better, though, is their performance as pampered prima donnas indoors, in warmth and light, where they grow to double height and spread-eagle their petals to flout their sex. I grow them in old clay thumb-pots and put them in the centre of the dinner table among the candles. They tilt and topple, gaping wide, purple, mauve and white with stamens golden in the candlelight. They last three days like this, but for this time they outshine (forgive me, orchids) any other midwinter flower.

The more you divide up a space the bigger it becomes. Scientific or not, I call it the Law of Immediate Surroundings. Your sense of space depends on what you can see; the only reason why tiny bedsits are habitable is that your vision accepts any limits you impose on it, and the rest of your senses, however reluctantly, follow.

I muse on this whenever I go down an arterial road lined with tiny houses cowering (if they are lucky) behind fences or hedges. At a pinch, I think, I could be content to make one of those cramped front rooms my space – because I could block off the outside world. My immediate surroundings are all I see. I could be snug.

The Royal Academy has just given a clutch of architects license to fool around with the space in its lofty galleries in an exhibition called Sensing Spaces. It’s not hard, with false walls and ceilings, mazes and mirrors, to produce confusion and disorientation – and the pleasant sensation of discovering ‘places’ that are illusory. Or are they?

Only recently I was writing (‘Displaced’, January 27) about what constitutes a place; the Academy show elaborates on the question.What about gardens, though? Isn’t this exactly what gardens are for? I would like to arrange a show that does something similar in garden terms, experimenting with opening views and blocking them off, introducing masses (as summer growth does as trees come into leaf, and tall perennials fill a border) and withdrawing them again. It would be fun to ape the process by inflating and deflating balloon models – at full scale, of course. Inflate a yew hedge to divide a space and see the effect, then try one with a completely different texture – the shine of camellias or laurel or the intricacy of bamboo. Or a brick wall.

I would try out pergolas and trellises, eye-catching statues, gazebos, benches and fountains (tricky, perhaps, with balloons). I would see what difference colour makes – with lights perhaps – turning, say, a white garden into a yellow or red one. How would we record the effect of each change on your mood, your engagement and curiosity? There will be a way, I’m sure, short of wiring up each visitor’s brain.

Indeed the whole thing could probably be done with designers’ software. But no, I want the full Academy experience – not forgetting garden scents and bursts of birdsong.

It's first flower opened in December. Can anyone name this camellia?

Squelching around Holland Park, as I do most afternoons, there is no mistaking the fact that spring has its foot in the door. Daffodils are opening their buds. The kerria in the Japanese garden is out; borage adds blue to the muddy tangle in a ditch. Porcelain-white Chaenomeles ‘Nivalis’ has been in flower for three weeks and what I took to be snowdrops in a lawn turned out as I got nearer to be daisies.

There has not, to my knowledge, been a single frost in London yet this winter. That ‘yet’ is important. The floods that are tormenting so much of the country amount to little more than puddles here, but I can’t remember any year when cold weather hasn’t arrived soon or later. I fear it may come in March, and remember with a shiver the weeks of East winds that last year made our departure from Saling Hall feel like a retreat from Moscow.

Are we getting a false impression of London life? I went out and picked a ripe lemon on the verandah last night from a tree happily flowering away in the rain. (Odd that rain doesn’t seem to inhibit the self-pollination of its endless flowers). The hawthorn on the roof outside my study is opening its buds three months ahead of schedule. The streets of Kensington are gay with camellias. I write this down so that I will believe it happened when things return to normal.

I can’t say I’m a connoisseur of garden centres; their combination of hoes and postcards, lasagne and water features, barbecues and whatever is in flower today may be a commercial necessity, but it somehow scrubs the part of any mind where plants and plans can usefully combine. I find myself filling the boot with things I’ve never wanted at ten percent off.

We made a detour, though, on our way home from Dolgellau, to visit Ashwood Nursery, near Stourbridge in a part of the country I don’t know at all. I had chanced on their website and been seduced by their choice of hellebores, daphnes, auriculas, hepaticas…the sort of things a gardener thinks of in winter. Especially a gardener with a tiny north-facing garden and a new greenhouse.

We were not disappointed. There was none of the usual corporate formula. It was clear straight away that this a nursery in the true sense of the word. Yes, the entrance/exit hall was full of china figurines (but even Kew trades in knick-knacks these days). Once past it, though, and the queue for the savoury-smelling café, the winter garden scene was perfect: intimate, enticing, jolly, with good plants and original ideas wherever you looked. The need for a gnome-land was handled with great applomb: you are greeted by a meadow of little model sheep. Then paths wind off through beds that look long-established and promising for all seasons, with enough January colour to spur you on; leading to glass houses on flower-show form, with the possibilities of the month excellently displayed and clearly explained.

No corporation, I thought, would have such taste or such high standards. Sadly we were there two weeks too early for the owner’s winter open garden day, but the photographs showed us what we were missing: a full-on demonstration of the possible, more personal and less stereotyped than any our public institutions give us. We shall be going back.

I. reticulata has passed though many hands, with many selections; this is apparently 'Pixie'.

Iris reticulata flowers two weeks after I. danfordiae – given identical conditions in the greenhouse. It has quite a different character though: a lady in party finery compared with a cheerful country girl. In the house her scent is quite different, too: more elusive, less nocturnal, delicate and piercing like a violet’s.

It has rained every day so far this year in North Wales – a state of affairs more unusual than you might think. The waterfalls are in splendid spate; just now we saw a group of daredevils canoeing down a fearsome sheer drop, free-falling through the spray. Our little river is in that sinister mood when it runs swift and silent, no ripples breaking its swirling surface. And the ground is saturated. I made the mistake of stepping off a hard track to skirt a fallen tree and went in to the top of one welly. Luckily not over the top, or I would have had to abandon it and limp back barefoot, the light quickly fading, half a mile downhill to the car – not a prospect to relish.

Worse, I was effectively lost. We have just clear-felled the spruce and larch on a wide stretch of hillside, and with the trees has gone all my sense of place. I was negotiating what had been a favourite bit of track, where tall trunks framed the first silver glimpses of the sea. Ferns were thick along the path, giving way to deep green moss and gleaming threads of water under the dark rows of trees. The track turned left here by a flat grey rock to skirt the steepest slope. There was no rock, and no track; just stumps and ruts and snaggy branches higgledy- piggledy everywhere. Getting back down in the dusk was tricky.

Forestry is a messy business; for long years calm, verdant, woken only by the flitting of birds; then suddenly the Somme. The place you knew and loved has ceased to exist. At least I am responsible, or at least obediently following the cycle of planting and harvesting. Foresters are to blame for the biggest changes anyone can perpetrate on the landscape, eliminating beautiful familiar places at a stroke.

So what is a “place”? How is it different from a map reference? A place has intelligence; it depends on understanding – of its purpose, its history, of the forces that flow through it. A landscape or garden designer’s job, or one of them, is to show you where to cast your eyes, and where to put your feet. There are forces at play in a design: sight-lines and pathways and the interplay between them. They are different in different seasons; winter transparency and summer solidity; the sun lower or higher in the sky; pale shadows and black obliterating ones. Colours, of course, and textures, eye-catchers and passages of restful green or grey.

All these contribute to a sense of place. They give you confidence, explain, perhaps subconsciously, where you are and why, what the gardener wants you to observe and enjoy, where you should go next to be excited or to be soothed into a reverie.

A resourceful gardener controls your mood; invites you to share his own, then changes it. It is the reason for the overwhelming success of garden rooms, of Hidcote and Sissinghurst and their many imitators. Great gardeners do it by suggestion, by modulating scale and colour, enclosing you or letting your eyes roam free, splashing water about or letting it reflect the sky: there are a thousand ways.

The forest will grow again – but it will be a different place.

There’s a limit to what the council will let you do to your trees in a leafy borough like this one. It has absolute power over the woody leafage. Not the power to plant a tree in your garden, of course, but the power to stop you disposing of it as you see fit. I am stuck, then, with a disproportionate amount of sycamore. I have reservations? A lack of proper respect? My problem: I bought the tree with the house.

In this privileged area, though, even the tree surgeons are a cut above the norms. I googled “Tree surgeons, Kensington” and stopped at the second name. Not a name to forget easily: Fergus Kinmonth – and one I recognised as a member of the International Dendrology Society and a visitor to our Essex garden. How many dendrologists climb trees with chainsaws? Probably not enough.

Fergus came round and we talked about the two trees that last summer kept the sun from touching our garden, the sycamore and the neighbour’s walnut. I know they get more than their share of publicity in this diary. But then they take more than their share of a diarist’s light.

Tooth-sucking from both of us. “They’ll let you take off the same as last time”, said Fergus. “That’s just the tips,” said I. “Precisely. This is a conservation area.” “So what is it they’re conserving?” “People don’t like it when the greenery they see from their windows is removed.”

I’m not keen, either, I admit. But here we have the politician’s dilemma. “If we want things to stay as they are, things will have to change” is not a message that public servants want to hear. So no radical tree surgery; just a snip here and there while the problem grows. Fergus and his team came and snipped – very handsomely and tidily, I must say. Not a twig is left: just a massive black tree-skeleton in the sky, ready to do the same again, plus a little bit – to need painful surgery again in a year or two.