It comes as a shock to see a cosseted house-plant making a nuisance of itself, rampaging away, smothering other plants, and generally calling for a dose of weed-killer. The sweet little winter-flowering jasmine, J polyanthum, wears an air of nursery innocence with its Mabel Lucy Attwell little girl complexion. No one would suspect what a thug it can become – until they see how it has behaved over the past winter in a London garden.

It has mounted and straddled our neighbour’s wall, climbed the unpruned roses waving five feet above it, smothered the ivy and launched shoots long enough to reach the ground and root on our side. A seedling has appeared on the other side of our garden too. The smell is divine, but the threat is manifest.Flowering began in December and is just past its climax. Admittedly there have only been a few nights of frost, but the idea that this is a tender hothouse thing has become absurd.

On our recent visit to California we saw it seeding prolifically, smothering rose bushes and climbing trees; the prettiest picture, but rather alarming. We read plenty of scary things about climate change, but a jasmine attack is something new.

The desert blooms

I’m writing this in the Getty Museum. Spring is taking about three days here on the coast of Southern California. I prefer our three month version, but it’s certainly exciting to sit under what’s known here as a sycamore and watch its pale velvet leaves expand before your eyes. With a tinge of regret, oddly enough: the silvery bark of the bare tree is so beautiful against the blue sky. I never saw a tree/building combination as effective as this: the sycamores, pruned back to truncheons at the end of each branch, against the white stone of these utterly modern but strangely classical buildings. I’m told that the credit for much of this; the uniformly white stone buildings and the almost obsessive number of trees, goes to the then head of Disney, the late Frank Wells.

We are staying nearby at Malibu in a garden he started 25 years ago on what was steep scrubland a mile from the Pacific. It gives me new respect for resolve, dollars – and cranes. On my previous visit, 25 years ago, I had misgivings about the 15 foot redwoods arriving with 4 foot rootballs to be planted at the improbably close spacing of a coastal redwood forest. In places, the trunks almost touched. It worked. And now they shelter an eye-opening collection of native and exotic plants, a cascade tumbling 200 feet to a lake, a creek that runs after storms, a horse ranch with Arabians, donkeys, Shetland ponies, goats, funny fluffy hens and flower and vegetable gardens, somehow disposed to feel organic parts of this manmade landscape.

The king of the native trees around Los Angeles is always the ‘sycamore’, one of the parents (with the Chennar tree of the Middle East) of the ‘London’ plane. They are paler than our planes, and apt to spread so wide in old age that they rest their white-barked elbows on the ground. The tree collection here runs from cherries and oranges and almonds to the giraffe of the palms, the immensely spindly and elegant Washingtonia. Camellias, magnolias, azaleas, roses, maples… name a desirable tree or shrub from Scotland to the Mediterranean or Hawaii and you’ll probably find it. Bauhinia purpurea or ‘Orchid Tree’, with flowers like an azalea (OK then, orchids), jacaranda, South African erithryna or ‘Coral Tree’ (not much Latin is used around here), covered in scarlet berries. Schinus molle, the drooping feathery Pepper Tree, is a beauty we could perhaps risk trying in the very south of England some day soon.

You need shelter from the sea winds here. That was part of the original purpose of the coast redwoods – and their western face can get singed brown by the salt. The steep hillside they shelter reminds me a little of La Mortola on the Riviera; paths that wind gently down in hairpin bends, bringing you close to all the planting. Everywhere you hear the cadence of the cascade and look round to catch a silvery glimpse.

The vegetable gardening is not humdrum either. The sandy soil is built up into beds here and there, formal and straight or in successive curves, in sun or shade, to grow every vegetable I could think of – except asparagus. Too specialized, says Tom, the head gardener. They grow it better on a farm along the coast.

The farmhouse is ‘Tuscan’, and startlingly realistic, with rooftiles shipped from Tuscany, an olive grove below and lemon terraces above. It could be Siena rather than Hollywood on the other side of the hills. But they have frosts in Tuscany. Here the Pacific is an air-conditioner, sending fog inland when it gets too hot. Or so they tell me.

'Phals' off to Beverley Hills

Do you have a pale-flowered orchid hovering nearby, in your bathroom, in your office, in the lobby? If it needs occasional watering, it’s a plant. If it doesn’t, it’s a pseudo-plant. You can also tell the difference by touching it.

The story of phalaenopsis, and its metamorphosis from rarity to banality, was told me in a California greenhouse where rows of identical plants stretched to the horizon in colour batches from white to fire-alarm magenta, green, cream, ginger…. anything but blue. There were monsters and miniatures, dressed by the right so that their identically-curved stems formed tunnels along the benches. At one end a team of Mexicans were potting up hundreds more. They were needed for a party in Beverley Hills.

The secret is, of course, micropropagation of stem cells of hybrids with lots of ploids. (My attention wandered during this part of the tour.) There are dozens of species, from the Himalayas to Australia; between them, it seems, almost anything is possible, and since the 1980s orchid nurseries have been on a roll. But so have whatever you call the nurseries that do fake flowers: the distinction is becoming blurred.

The purist in me sees the multiplication of varieties, and the endless novelties with their twee names, as a sort of betrayal. This is not what gardening is about. I would rather struggle to cultivate a creation of nature in all its simplicity than choose between the latest colour-ways of something man-made. Am I just being po-faced? Or has it nothing to do with gardening?

Buckeye comes indoors, chez Molly Chappellet

Days are warm and nights cold in February in the Napa valley. Wine-growers prefer cold, fearing budbreak too early and tender new shoots in the frosts of March and April. Hence the surprising sight of vineyards unpruned, still with their tangled tophamper, when much of Europe gets started with the new year.

After four years of drought the valley is celebrating a week of heavy rain. Brilliant green grass is a rare sight here; all summer the fields are buff or brown, but now the hills are emerald under the ghost-grey oaks festooned with Spanish moss. The vineyard cover-crop of mustard is celebratory yellow, the almond trees in every yard pale pink (two colours to keep apart if you can). Explosions of mimosa are over; magnolias are well away, and in the hillside grass blue borage, the first orange poppies, blue lupins and the tiny magenta Dodecatheons or shooting stars, primulaceous plants with swept-back petals rather like cyclamen.

But my favourites are the buckeyes, Aesculus californica. They form the lower layer of the forest, under oak, redwood and fir, with the gleaming madrones, the western version of our strawberry trees. Buckeyes break into leaf before almost any tree, salad-green in the bare undergrowth. Cold doesn’t seem to bother them. In early summer their long candles are as elaborately detailed as orchids. By late summer their leaves yellow and fall, leaving their grey tracery, wider than high, dripping with shining teardrop-shaped conkers.

For several years I collected them on Napa hillsides at vintage time and took them home. I planted them but they never germinated. Then one year I scooped some up on the way to the airport. They were in pots the same day and came up as eagerly as horse chestnuts. In fifteen years we were on the third generation.

There is one tree here I would love to plant at home; the luscious pale green and very faintly blushing Cinnamomum camphora that spreads its long branches over many Japanese shrines. It catches your eye in any group of trees, looking edibly tender – which in England, sadly, it is.

Current residents of the Round Pond

It’s something you don’t normally see in a city park, certainly not a Royal one. The grass is left uncut and the trees allowed to seed at random. Oak and sweet chestnuts and hawthorns come up haphazard in the brown grass. It’s a long way from the total control which seems to be the norm in public spaces.

Kensington Gardens, though, is run on unusual lines. The gardens were designed for the Royal family in the first decades of the 18th century, and there seems no good reason to change them now.

I like to picture the Kensington of the early 1700s, a country village with two great houses, Holland House and the rapidly growing Kensington Palace. Gardening was its main industry: the Brompton Park Nursery, roughly where the Albert Hall stands, was the country’s biggest by far (at one time it grew 10 million plants on 50 acres). One of its original founders, George London, recruited Henry Wise as his partner; together they planned and supplied the new gardens at Hampton Court, Blenheim, Castle Howard, Longleat, Chatsworth, Burghley – and Kensington Palace. William and Mary had brought in the Dutch style you still see in the sunk garden at Kensington. Everyone wanted to go Dutch. Wagon after wagon laden with trees and plants splashed along Kensington Road bound for country estates.

In due course Wise was appointed Royal gardener and drew up the scheme for Kensington Gardens in the then prevailing Franco-Dutch style (a bit of Het Loo; a bit of Versailles), with avenues radiating from the palace, or rather from the Round Pond he designed as the centre of a patte d’oie. The areas between the avenues were designated as ‘quarters’, some planted as ‘bosquets’ or shady groves, some as embroidered parterres, some as ‘wilderness’ with winding paths among shrubs and trees, some left as pasture. Altogether, they cover 275 acres. Hyde Park to the east covers 350 acres.

On the eastern boundary of Kensington Gardens you can still see two of the three ‘bastions’, looking like gun emplacements, that faced London, whether in serious or symbolic challenge I’m not sure. The succession from Henry Wise to Charles Bridgeman to William Kent, all of them involved in the gardens, is not very clear. Bridgeman (another gardener’s son) joined the Brompton Park Nursery, was promoted to Royal gardener jointly with Wise, and gets credit for the lake we call the Serpentine, made by damming the river Westbourne. Bridgeman was on the way to the unbuttoned style of Capability Brown, but he still surrounded his ‘quarters’ with hedges.

Bridgeman’s drawing of the gardens in 1733 shows the ‘quarters’ as distinct entities. Those nearer the palace, round the Round Pond (‘The Bason’) were all wiggly paths through shrubberies. North of the Palace (where the Duke of Cambridge now lands his helicopter) there were classic geometrical parterres. To the south, very much the lawns with the tree-alleys you see today. Further east, the main avenues have scarcely changed – except in the species of trees.There were open fields: the Horse Quarter, Colt Quarter, Rye Grass Quarter and Temple Quarter. Between the Round Pond and Kensington Road was the Old Pond Quarter where there was another pond (and there is now a spring).

This is the plan that is being maintained today as faithfully as possible – including the long grass and seedlings. Avenues are the trickiest part. Tree-managers are constantly faced with decisions about whether to replace old trees that fall or die or become unsafe. Should they use the same species (usually yes) or admit that a gradual change-over would be better in the long run? The Broad Walk, for example, was given an inner line of Norway maples (the outer is lime) fifty years ago. People love their early flowers and yellow autumn colour. But the squirrels love their bark and destroy the upper trunk. Squirrel control? Tell that to the tourists.

The maples will, in due course, be replaced – probably with sessile oaks. Originally lime and oak, elm and sweet chestnut were the principal trees. The planes and sadly ailing horse chestnuts are mainly Victorian planting – and thank heaven for the planes; since the elms died (there was more elm in Hyde Park) planes are by far the grandest trees. The grandest are in the main north-south avenue, with the Statue of Physical Energy at its centre, known as the Lancaster Gate Walk. There is an amusing anomaly here. When the Albert Memorial was built, in 1870, it obviously called for an avenue, but the existing one was out of alignment with it. The answer was to ‘splice’ on two new lines of trees to link with the existing ones: hence two converging avenues (and a magnificent cluster of planes) at the Memorial end. No one talks of replacing these trees: if they look tired the gardeners give them a boost, aerate their roots and spread mulch in a wide circle round their trunks.

Limes are now coming to the fore as the dominant species – at least in numbers. Last year, 50-odd new limes were planted; very noticeably in ‘The Great Bow’ round the Round Pond. They are very noticeable on Bridgeman’s plan, too. Plus ça change.

It was the smell that gave me a shock. I took a shortcut through Ravenscourt Park, rounded a corner, and was hit by a midsummer blast of mown grass – the sweetest of all garden smells. The early daffodils lined the path, magnolias were opening their buds, a big mimosa had almost finished flowering, crocuses dotted the lawn and the cherry decorating the path with its fallen petals was not Prunus autumnalis. We have to reclassify Jasminum polyanthum now from pot plant to exceedingly vigorous climber.

This must be the strangest winter London has ever seen. March may blast it all away, of course, but I am more worried about the spring. There won’t be one if it’s all happened already.

Anticipation is so important. Excitement as each bud opens and flowers gradually make their appearance. But what if you are looking forward to a concert and you keep hearing the soloists, with no warning, loosing off in the street, under your window, out of context? In the end, there is no concert; they have all sung their hearts out and have nothing left to give. That’s what I fear. Last year Bonfire Night dragged on for weeks as people let off their fireworks whenever they felt like it. I don’t want to see spring dissipated, limping along week after week.

Every gardener will have his own tale of cock-eyed timing. Roger Taylor of Taylor’s Bulbs tells me that his Lincolnshire daffs started flowering in sync with Cornwall’s – spoiling both their markets. There is hawthorn in leaf in roadside hedgerows. And my own: Pelargonium x ardens, the fiery-red one that sprawls over its neighbours in late summer, has shot straight up three feet like a tree sapling and is flowering in the apex of the greenhouse roof.

Quieter, just as loving: Melbourne Hall by George Elgood 1892

It’s the moment that makes a good photo – far more than the aperture. Does anyone say that Capa’s shot of a Spanish soldier dying needs more focal depth, or the lovers kissing on a Paris street could do with more light?

Which suggests that our camera-phones, or phone-cameras, have a better chance of taking good photos than more sophisticated kit, proper cameras that need adjustment. Their margin of error is astonishing: if you know even the rudiments of photography, you have the ideal weapon to hand.

And what does the perfect moment consist of? A soldier just cut down, a moment of passion in the street are messages about death and love; nothing could be more elemental. In both these famous photos there are no distractions, no other people, no fussy backdrops, chance has isolated the protagonists and made them sculptural.

A plant, a garden or a landscape can seem elemental, too: but what makes it so? Of course the light. A shaft or beam picking out an object, whether from the front, the side or from behind, is the most obvious way of making a point – a picture with, as it were, its caption built in. Conversely, a bright general light with only one object caught unlit could make a different point. Shooting into the source of light, contre jour, can be the best way of characterising certain plants: pale flowers, for example, with their petals glowing, their veins minutely delineated. The sun setting behind flowering grasses….

The artist with his brushes has always had the advantage over the photographer. He doesn’t have to wait for the light to strike. He can store moments in his memory to reproduce, work on, elaborate and combine at leisure. Did Monet grab his palette and rush out into the garden when the sun broke through? Maybe. He was an artist-showman (dare I mention Damian Hirst?) building up a body of garden impressions to create a market primed for his output. Wouldn’t he have loved an iPhone?

The show at the Royal Academy now (I believe there are a dozen Monets) is called Painting the Garden. Is there any room for quieter, smaller, but just as loving garden paintings by British artists? Or even for David Hockney’s all-encompassing woodlands – surely the modern equivalent of Giverny?

Bengal Crimson - in January?

To the Chelsea Physic Garden for their annual snowdrop show. I’m afraid they have been blind-sided by the weather: it has been so mild that they had moved the date forward by two weeks, only for the long-awaited cold to descend just before the new opening date. So no carpets of 10, 000 snowdrops, just the earliest species and a lot of promising little spears. The best part was the sales tent, where a room was ingeniously separated and blacked out for a little theatre of the best varieties lit by ultra-violet light: a pretty conceit.

I was happy to find an old friend for sale, too: Hardenbergia violacea, a little Australian climber that produces its racemes of purple flowers at snowdrop time, and for weeks before and after. It was a principal mid-winter decoration in our old conservatory. I shall have to be quite severe with it in our tiny greenhouse, but it might as well have the roof-space now filled with Jasminum polyanthum, which can’t even keep up with the one flowering fit to bust above the wall outside. I wonder why. Perhaps because it feels undernourished in its 12-inch pot.

The outstanding plant in the C.P.G. yesterday was Daphne bholua ‘Jacqueline Postill’ in the border by the fern house, a shrub now twelve feet wide and nine high. There is no need to walk over: the scent reaches across the lawn. Is there any plant of recent introduction to beat it? (And who, by the way, is or was Jacqueline?) The Rosa odorata, near the Tangerine Dream café, was even more fully in flower than last year, covered with a hundred little light-crimson butterfly-like blooms and their fragile fresh leaves, pale green flushed red, as though it was May. I still prefer the old name R. spontanea ‘Bengal Crimson’, but I hardly dare say so.