Trees may be slow but forests are fast. That’s how it seems to me in our Welsh woods. We were honoured last year with a visit from the Royal Forestry Society (or at least its North Wales Division), and I recalled how things have changed in the 29 years we have been in charge.

What is still recognizable are the contours; slopes of five hundred feet or so from the valley to a ridge, commanding a huge view across the sea towards the Wicklow Hills, and south to the rocky north face of Cader Idris (a mountain more noted for its bulk than its height). That is the airy mountain component. The rushy glen is the course of the Afon Dwynant, from a few springs high on the hill to a burbling, occasionally rushing stream as wide as a country road that eventually tips into the estuary of the Mawdach. The estuary is lined with what is termed ‘Atlantic Oak Woodland’, a precious zone where contorted oaks thrust up from a bed of boulders with only moss and ferns for company. Last year there was no rain for week after week. The hillside springs were dry, with a surprising effect: without moisture they appeared as brown, even scorched, patches in the grass and heather.

The rotation of a commercial forest (as much of ours is) is about sixty years. The tallest remaining trees from the last major plantation , in the 1990s, are spruces almost a hundred feet high and larches, perhaps eighty feet but incomparably beautiful, their delicate canopies soaring on ramrod trunks to form airy colonnades.

Foresters talk about ‘yield-class’, a figure denoting the number of cubic metres of timber produced in a year per hectare – depending, of course, on many factors. Inevitably, sadly, the star performers are always the aggressive Sitka spruce, black in the landscape, spiky to touch. They don’t seem to care if it’s bog or rock; you don’t even have to plant them; their self-sown seedlings sprout everywhere. Foresters say ‘re-gen’, often so dense that it needs ‘re-spacing’.

Our policy is to leaven our money-making blocks of Sitka with admixtures of other conifers, usually larch, or a scattering of broadleaves, which could be beech, birch (which comes up anyway), alder, wild cherry or even Norway maple. Oak is too slow in getting started. Larch, tragically, is suffering and dying from a virulent form of Phytophthora. The lovely Western hemlock, with drooping sprays of bright apple green, is prolific, and can be vigorous enough to hold its own – though sadly sawmills, the market for all our trees, have problems using it and prefer the conventional spruce. Then there is birch and rowan, the sweet-smelling gorse, and of course bracken and brambles. The forest is never dull.

Sixteen degrees on February 16 doesn’t sound or feel right. The magnolia in the front garden looks ready to burst its buds. Primroses are even fading on the north side of the house. Daphnes are in full fragrant flower and the flowering currant is already giving off its Marmite smell. Camellias are in full bloom and in the water tank the fish look distinctly frisky.

Last night we slept with the French windows open. We see summer blouses on the street. The weather forecast shows no hint of winter returning to duty. Should we be alarmed? And is there anything we can do?

The horticultural answer is yes: take advantage. And take precautions. Bring the swelling buds into the house and try to stop the greenhouse from becoming a hot house by shading during the day and ventilating day and night.

Now its February 20; the mercury has dropped three degrees and low clouds have hidden the sun. The magnolia has shed all its furry bracts, leaving its purple flowers closed but naked like dark flames among the grey branches. The cercidiphyllum that hangs weeping over our boundary and the pavement is opening its first tiny heart-shaped leaves at the tip of each branch. Crocuses that have found their way into the front garden beds are starting to clump up, and a fresh crop of purple flowers are pushing up through the tangle of leaves of Iris unguicularis. It’s a badly designed plant; its leaves succeed in hiding its flowers.

A fat bag of mulch has just arrived form Rassell’s nursery across Earls Court Road. Spreading it is my next job.

Mist has gathered in the valley where sheep dot the emerald green with white. High on the hill it blows in scraps and longer straggling clouds across the black of spruce and fir. Between the two sun is reaching a tapestry of trees, finding bright gold in the larches, richer, deeper gold in maples, bone-grey in ashes and a lively yellow-brown in the swathes of bracken. Bracken in the sun is the dominant eye-catcher, and seems to grow more dominant every year.

You get the feeling, sometimes, that bracken will one day smother everything. Yet it’s scarcely a new invention. The diary of the farmer at Sylfaen next door in the 1870s speaks of the bracken-crop in autumn as one of the worst tasks of the year, It was used for animal bedding, but gathering it meant breathing in clouds of its spores, which turned out to be carcinogenic.

Bracken is apparently a universal weed. Antarctica is the only continent without it. It can grow up to ten feet high and spread with its rhizomes hundreds of yards. It won’t grow in boggy ground, so the drainage of uplands only encourages it, but is otherwise unfussy about soils. It laughs off authorized weedkillers. Its roots survive the sharp trotters of sheep. Clodhopping cows are better at breaking them up, but only repeated trampling year after year suppresses them. So expect to see more of it somewhere near you.

Not many people are lucky enough to have time and space to plant an arboretum, let alone nurture it until the trees reach maturity. The fact that I am now on my second argues the devil’s luck – which I happily acknowledge. My first (to deserve the name) is growing, flourishing indeed, at Saling Hall in Essex, where we lived for 42 years. The second is taking shape at our daughter’s house on the fringe of the New Forest and only two miles from the sea. (That is not counting a much earlier effort on the North Downs in Kent; nothing to see here, as Constable Plod would say, but evidence of an urge to put roots in the ground; roots that would lead in time to a contribution to the landscape.)

Sceptics have often told me that nothing much would happen for so long that I shouldn’t bother. You can argue that a tree doesn’t merit the name until you can stand in its shade. Nonsense, I answer: I want to see its leading shoot up close, at eye level; see which buds open in what order, watch the shoot with the most vim take the lead, defy gravity and head straight north and the others accept their fate and become mere branches.

It was John Claudius Loudon, by the way, who coined the word arboretum. Who indeed originated many of the terms and ideas we now accept as fundamental to the language of gardening. Every time I pass his house in the Bayswater Road (number 3, Porchester Terrace) I remember this extraordinary work-driven Scotsman, traveller, designer (of greenhouses and cemeteries) and all-round gardening visionary. His encyclopaedias, two bricks thick, and The Garden Magazine, which he founded and ‘conducted’ from 1826 to 1844, laid down the ground-rules of Victorian gardening – many of which survive in essence to our days. His wife Jane’s contributions were just as impressive. Loudon lost his right arm and was a rheumatic invalid all his life, the son of a farmer in the Borders who achieved more for horticulture than anyone of his time.

There are two plants I’ve kept in pots for longer than I can remember. Even the same pots. Both of them start to strut their stuff at this time of year, when the garden is winding down. Nandina domestica doesn’t have a traditional garden name,  becomes a flourish of narrow red leaves, and Meyer’s Lemon’s lemons ripen to bright pale yellow among its glossy green leaves. The lemon has occupied its handsome Tuscan pot, decorated with moulded lemons, for more than 35 years, its soil unchanged, except for the two inches of compost I dress it with in winter. It hasn’t seen the sun for the past ten years, being on our north-facing verandah. I water it weekly in summer, scarcely ever in winter. The fruit I picked last week, thin-skinned but juicy, was as close as lemons get to sweet.

The nandina, Nanten in Japanese and Sacred Bamboo in America, was a berry in the botanical garden at Kobe, on the south coast of Japan. I picked the berries because they were yellow rather than the usual red. The nanten is Japan’s doorstep plant, the traditional welcome, standing on the stone threshold that is kept wet, furnished with a fresh pile of salt, to welcome visitors. Superstition says the salt wards off evil spirits. Another story is that it attracts the draught oxen that once pulled important people’s wagons. The salt, they say, signalled complaisant ladies within.

Back home from two weeks in fire-scorched California. How glad I am to live in England’s moderate, rarely dramatic, climate. The Mediterranean climate has its points for holidays, but who wants endless sunshine, endless yearning for rain?  Certainly not me. Why do so many sports originate – or certainly flourish – in Britain? Because there are relatively few days in the year when it’s not a pleasure to be outdoors

The wine-country hills north of San Francisco last month were a terrible sight. Normally its rolling grassland, scattered with spreading trees, has the air of a park done in Van Gogh colours: tawny-gold grass; dark silhouettes of widely-spaced oaks. This year the grass, tall after good spring rains, was tinder. A windblown spark could start a new fire hundreds of yards away. Wildfires race from field to field, then from hill to hill, almost as rapidly as your eye could follow – and there are dwellings everywhere in this golden country. Your life could depend on whether you parked your car facing the way out to the road.,

The climate of coastal California depends on winds from the benign Pacific alongside. Its cold water, icy currents from Alaska, sends walls of fog, ranging from gauze to blanket, daily creeping inland. Coastal hills block them; such gaps in the hills as the Golden Gate give them access. The fertility of the Golden State; and certainly the quality of its wine, depends on them. But drought is its default condition, and fire a constant hazard.

It spares no one. Meadowood is a country club at the upper end of the Napa Valley. Of its social structure, too. Its scores of bedrooms are scattered in ‘lodges’ among the trees. The fires burnt three quarters of them, and the main building, to the ground. Undaunted, what was left was in full swing only a few months later.

It is a two-hour drive west from Napa to the ocean, through placid pasture, redwood ranch-houses and herds of cows – even the occasional cowboy – to Bodega Bay, where long Pacific rollers crash on the rocky coast. A hundred and fifty years ago all this land was forest, to be felled in the 20^th century to build the houses of the Bay Area. It’s hard to imagine the process of felling and transporting trees 300 feet high – with axes. A few token remnants of this vast woodland are preserved: Armstrong Woods is one: its 1,800 acres of sequoias still maintain their fragrant forest humidity, thanks to the Pacific fogs, but even here the colossal trees are scarred by fire.

Green Provence is another country. The tawny arable plain painted by Van Gogh gives way, east of Aix and Mont Ste Victoire, to a fresh green (a pale, almost apple green) forest of pines covering endless confused hills. They are Aleppo pines, sinuous, pale-trunked, with needles in pairs, found largely along the Mediterranean coast. Off to the south the Massif des Maures shelters the bays of the Corniche: Le Lavendou and St Tropez. Green Provence keeps going, a forest to the horizon interspersed with insubstantial towns; Brignoles and Draguignan the biggest. Quiet villages of buff and ochre houses are clustered around with olive groves and patches of vines never big enough to suggest an industry.

A lazy little river, the Argens, as silvery as its name suggests, winds slowly east to the Mediterranean at Fréjus. Correns, one of the villages on its course has distinguished itself by being the first commune in France to declare itself entirely ‘Bio.’ I am writing this there, in a little rather stiff-looking chateau facing south down to the river, its wide gravel terrace, dedicated to boules, shaded by magnificent pollard plane trees that could be its contemporaries. They cast huge shadows on its yellow walls and fourteen grey-shuttered windows. Its provincial formality evokes the novels of Flaubert and Balzac. What domestic dramas, what frustrated passions have its tall ceilings seen, and heard the slamming of its panelled doors?

An amphitheatre of low hills forms a barrier to the dreaded Mistral cutting down from the north. The forest here burned a few years ago, laying bare a pattern of buff stone terraces, gradually greening as the maquis takes over again. The house and garden sit on three steep-terraced levels, their stillness tinkled into life by the spring that must have inspired the builder to settle here.

The flora of a Provencal garden is predictable; a reassuring sameness of olive and vine and almond, fig trees and plane trees. In old properties the plane trees are multi-stemmed monsters mottled yellow and grey. Dark cypresses can be either the classic rocket shape or branchy and nondescript. In this garden they vary from nondescript to so severely, tightly, narrow it is hard to believe no wire corset is involved. Rosemary, lavender and cistus are the predominant low shrubs. A belt of grey olive trees surrounds the garden. Then the green monotony of vines.

You could have taken it for one of the many vineyards appearing all over Essex, taking advantage of the country’s sunshine records.  But no: they’re blackcurrant bushes, rank upon rank, acre upon acre. I had never wondered where Ribena comes from; now I know. It’s the valley of the river Blackwater, a lazy stream that starts as the Pant, becomes the Brain, then changes its name once more and finally meets the Thames Estuary between Maldon and West  Mersea in a flurry of activity: oysters, salt production and celebrities. The tidal causeway to Osea Island is familiar to singers using its recording studios.

We lived in Essex for forty years. We learned to counter its reputation as a flat and boring county. ‘No’, we used to say ‘Its undulating and boring.’ It certainly undulates, silver cricket bat willows marking the low points, its water courses, while its boredom is relieved by village streets of ancient gabled houses plastered in many colours.

In the water meadows along the river you wade through the lush grass, your knees soaked, scarcely able to tell where the grass ends and the weed-choked water begins, your head snared by the congestion of willows. Ratty would love it. Perhaps this is where he and his friends live.

We stayed with friends who cultivate blackcurrants in large numbers and provoke my envy in possessing a thing I have longed for all my life: a gushing spring at the top of the garden. The last bit is the most important. A spring at the bottom will give you a fine pond; possibly a stream. At the top it gives you all the energy of falling water. Theirs fills a calm broad pond, then overflows over a little wooden waterwheel  into a tumbling brook to another pond, and then another, until it slithers through the willows into the tall grass and into the Blackwater.

In our Welsh woods we have water rushing over rocks, wild, glittering, noisy, untameable. My urge is to placate it, put a dam in its way, tranquilize it; arrest all that urgency. It is the converse of my poking about with stick and leaves to induce a tiny stream. Idleness (mine) meets elemental energy and treats it as a toy.