Tea on the lawn on a baking day with the hospitable Bleddyn and Sue Wynn-Jones of Crug Farm plans, the foreground a field of cows, the background the Llanberis Pass deep into Snowdonia. Every visit to Crug Farm is a revelation of plants I’ve never seen before. Sometimes I can spot the genus, very rarely the species: Sue and Bleddyn still don’t have names for half the plants they grow: just accession numbers. And the numbers grow lustily each time they do a trawl in South East Asia or Central America, two of their main collecting grounds.

They list over 60 trips on their website, starting in 1992. They collect friends, too: that day a Belgium nurseryman and his wife, every day a plantsman from near or far agog to see what new things they are offering in their little sales yard, or growing in their propagating tunnels, or displaying in their romantically intricate little gardens between the house and the old farm buildings.

Last year they saw an accidental fire as a chance to add yet another garden. An old cow barn went up in flames; leaving its walls and the remains of its roof as a sheltering spot for yet more new plants whose hardiness needs testing. It is a completely eclectic mix, from maples to lilies – all with a new twist – via fifty things I’ve never heard of. Scheffleras seem to be a Crug signature plant (they list 31 in their astonishing catalogue). Their elegant almost palm-like clumps and fingered leaves caught my eye several times, some with discreet yellow flowers, some with black berries. But it is absurd to pick on any plant, or even genus, in this garden of wonders. We left feeling as though the Creator had had another go with a new designer.

Plas yn Rhiw

I don’t suppose the name Plas yn Rhiw comes up very often at meetings of the National Trust Gardens Committee. If there was a period when a sense of horticultural correctness pervaded the Trust’s gardens, you wouldn’t know it here, around this remote little manor house on the Llyn Peninsula, stuck out in the Irish Sea. A sense of place certainly: it would be bizarre not to plant the sort of half-hardy things the benign sea air allows. Of fashion, inevitably: bright gardeners are always alert to new plants coming through the system. But, most agreeably, a sense of freedom to be as relaxed as befits minor provincial gentry happily hidden from the world.

The “Plas”, a word which in Welsh seems to cover anything from a mansion to a very minor manor, was restored by three spinster sisters from Nottingham in the 1940’s, encouraged by their friend Clough Williams Ellis of Portmeirion. Everything from the books in the bookshelves to the box-hedged enclosures of the garden bursting with exotic shrubs breathes an austere gentility in speaking contrast to tremendous views of sea and mountains.

The mansion “Plas” of these parts is Plas Newydd, the huge house of the Marquesses of Anglesey on the Menai Strait, in the front row of the stalls for the rock and cloud performances of Mount Snowdon. The National Trust plays this with a light hand, too: it is part family house, part museum (with Rex Whistler’s most famous mural as its USP). One formal terrace, the Royal Box as it were, is intensely floral: blue white and grey in the view that includes the mountains, hellfire red looking the other way.

Trees grow magnificently in its sheltered seaside policies. There is a macrocarpa avenue where these usually scruffy windbreak trees grow as straight grey pillars 80 feet high. Hydrangeas are a way of life in these parts; you pass walls of them hundreds of yards long on the way to the arboretum, with elephantine beeches supervising a jungle of visitors from down under: eucalyptus and every kind of southern beech.

Something we noticed everywhere this year: hydrangeas are ignoring all the colour conventions. The same plant has flowers from imperial purple to Cambridge blue. Is it the warm spring, the sunny summer, or just perversity?

The view from the woods, south to Cader Idris, Wales's Table Mountain

Forestry is inherently an untidy business. Each summer we come to North Wales to enjoy our woods, the mountains round and sea below, and each year another patch is a (temporary) eyesore. This year is a bad one: the February gales made a shambles of half a hillside, and fishing the trees out from the mess transferred a good deal of it onto the forest track. Ditches had to be scoured, surfaces scraped and loads of new stone spread and rolled in. Luckily we have a good roadstone quarry in the heart of the forest, but I have to admit there is a certain rawness about parts of the place just now.

It is easy to escape them. The bosom of the broadleaves is where I go, where a stream tumbles down white among the black rocks. There is a line of Milton’s that rings in my head here: ‘bosom’d high in tufted trees’. The distinct tufts of well-spaced oaks and beeches, ashes, some sycamores and innumerable birches pattern the hillside opposite like a gallery of portraits, now glowing gold in the evening sun. I have been surprised to learn how often a wood of originally close-planted trees needs thinning to make strong (as opposed to spindly) trunks: perhaps once every fifteen years. I wonder where Milton’s trees were.

Ashes are a worry: Chalara may well be on the way to kill or cripple them. But I never planted many; there are plenty of seedlings, and oak and beech are our favourites. The far bigger worry is the new threat to the larch from the dreaded Phytophthora ramorum that arrived in Wales from the southwest and seems to be heading north. Almost a quarter of our trees are larch, most of them planted in the 1960s and now close to full height. For ten years we have been thinning them; they need maximum light to form strong heads on their elegant bare stems, standing thirty feet or so apart. The forestry plan is to underplant them with beech or Douglas fir (or both), so when they are felled at full size the ground is already well treed. There is a good deal of volunteer oak and birch too. We hate the idea of losing the pale larch-green in spring and warm gold in autumn, born high above the hillsides on graceful poles.

It is strange to remember that larches only came to this country in the 1600s from the Alps. John Evelyn in his Sylva tells how his gardener threw out his first batch of seedlings in the first winter, thinking their loss of needles meant they had died. He goes on to rave about the quality of larch timber, as good as oak for shipbuilding, able to be sliced so thin that you could use it in place of glass in a window and light would shine through.

We visited the biggest larch in the Alps, in the Val d’Anniviers, this spring, a branchy, craggy monster supposedly born in about 1600. Some of Britain’s original trees still grow at Dunkeld, where they were planted 300 years ago by the Duke of Atholl. I can’t bear to think that we could lose all these lovely trees..

Rozanne is happy anywhere

There have been just enough hot sunny days to remind me how much I prefer the shade to sitting, or walking, or doing almost anything in the sun. Shade, that is, with sun round the edges; pools of shade, as under trees, for example. Perhaps I am like a camera film that renders the shady foreground well enough., but can’t handle the light beyond. The image burns out.

The garden is close to monochrome at present, or rather we have so many flowers in the hard-to-name purpley-bluey-lavender-violet range that it looks as though I’ve done it on purpose. They take their cue, it seems, from The Geranium of the Millenium – for surely Rozanne has earned that title. You see her everywhere, as you did Verbena bonariensis a year or two ago – and still do in this garden. Come to that their colours are both in the same part of the spectrum.

So are the little viola that spent the winter in a pot indoors and gamely flowers on in her summer quarters, Campanula persicifolia, a catananche I’ve taken up with, Tulbaghia violacea, which I’m told is rather charmingly known as Society Garlic, and the best of all summer clematis, Perle d’Azur. The newer and smaller Prince Charles is a relatively feeble version of the same colour.

I can’t be held responsible for the roses that flourish high above the wall on our neighbour’s side. They make sure no colour scheme of ours will survive. But do I mind? No, I’m not a schemer at heart, and their Wars of the Roses red and white is a splendid statement. Then on our side there’s Iceberg, Gloire de Dijon, Alister Stella Gray – all our old favourites – and Bantry Bay (perhaps a mistake; pink looks like a compromise).

What astonishes me is how much water everything wants. Above all, of course, the pots. When we go to Wales for two weeks I shall rely entirely on a newly-acquired Aqua-Pod dripper system. The landlord of the corner pub nourishes a lurid display with it. But then he doesn’t take a fortnight off in Wales.

Tilia petiolaris, the weeping silver lime, in flower at Kew

To Kew yesterday for a linden-bath. That was the sensation as I walked in through the Victoria Gate. Straight ahead stands a big common lime, taller than a church and as wide as two, covered with its pale drooping flowers – and pumping out essence of mid-summer.

Turn left past the little temple and a huge weeping silver lime, Tilia petiolaris, is spreading its skirts in front of you, embalming the air. Then they come thick and fast, one species after another, a whole wood of limes, from a squatly spreading small-leaved one, Tilia cordata, like a green and yellow cushion, to soaring T. petiolaris, surely some of Kew’s tallest trees. It is a curious fact about this splendid species (or is it a cultivar?) that it habitually divides into two, or often three, major trunks about twenty feet from the ground. They grow vertically with mighty vigour to make a majestic tower, their leaf-stalks (the petioles of petiolaris) twisting to show the silver-white undersides of the leaves. At this moment its cascading flowers are just opening and beginning to shower down their scent. More limes stand ready for their later flowering, with the fringe-leafed T. henryana from China coming last.

I headed towards the river from this honey-scented zone, skirting the sickly smell of the sweet chestnuts, to visit the Mediterranean area with its perfectly authentic-looking olive grove in a patch of rock-strewn garrigue and the cork oak forest next to it. A huge cork oak lies prone amid citrus and seedling pines next to a signboard exerting us to protect this threatened habitat. Threatened, among other things, by the spread of screw-capped wine bottles and consequent decline in demand for corks.

I’m not sure about this. The demand for wine-corks has grown exponentially in the past thirty or forty years, since wine became the popular drink it is today. In the past a relatively small proportion was given the dignity of a cork and capsule. Cork had many other uses, from buoyancy aids to insulation to high heels, but any increase in oak-acreage due to wine must be pretty recent. It’s not screw caps we should blame, but substitutes for its other uses. Let’s have more cork-tiled floors – and thank goodness we’re seeing the decline of the corkscrew.

Trachelospermum jasminoides

Christopher Bailes, the about-to-retire curator of the Chelsea Physic Garden, reckons his plants are between four to six weeks ahead of schedule this summer. Who knows how much of the advance is due to the mild spring after a mild wet winter, and how much to the famously privileged site, surrounded by buildings on the banks of the Thames? The garden has, after all, England’s biggest and oldest olive tree, a serious cork oak and scores of plants considered tender everywhere else.

Hoheria sexstylosa grows here to substantial tree size, palm trees include Jubaea and Washingtonia, the proper working tobacco plant, Nicotiana tabacum, has become a shrub, now in full pink flower. There is a fruiting grapefruit tree and an avocado…no, this is no ordinary London garden. Yet walking there through Chelsea I realise what a hothouse London in general has become. The plant of the moment, to the point of monotony, is Trachelospermum jasminoides , scrambling up walls, dangling from trees, often in its variegated form, a pale presence in expensive front gardens it seems almost everywhere.

No wonder. It is decorative, vigorous and now apparently reliably hardy. It casts a sweet but not obvious jasminoid smell about it. It only needs a little help from a trellis to reach ten feet or more. The cream-variegated form is less vigorous and maybe less hardy, but given a bit of care can be smart as paint.

What else do we know from its family, the Apocynaceae? Periwinkle is perhaps best-known. Also mandevilla and nerium, the common oleander. A trachelospermum in periwinkle blue (or in oleander pink) would be popular.

An easy trio that works beautifully in London, scrambling along a fence, hiding the neighbours and giving us all pretty colours over the summer. Clematis ‘Perle d’Azur’, Solanum jasminoides ‘Alba’ and Eccremocarpus scaber ‘Tresco Gold’.

The solanum is a big commitment; a powerful plant that wanders everywhere. The clematis is no wimp, either, but flowers as reliably as any of it kind. The eccremocarpus is on a smaller scale, flimsy-looking but well able to keep up for a year or two. Then some hard pruning is needed.

Whether the last is truly ‘Tresco Gold’ I’m not sure; I grew it from seed from an old plant in another garden.

Gardening has its heydays, and this is one of them. Do you remember how pessimistic we were about it in the 1970s? Perhaps not, but Trad was there, editorialising in The Garden about the lack of gardeners and the money to pay them, and the desperate need to conserve what little was left of our gardening heritage. Worried groups were forming to protect gardens and plants (the NCCPG was Graham Thomas’s idea), and to rekindle the very notion of garden history. 1978 was when we published the first Conservation Issue of the RHS Journal. How much has changed.

These were my thoughts in two gardens I visited recently, thanks to the Garden Museum and its super-charged director, Christopher Woodward. The first is a mere ten years old, and still a bit of a secret, but already gives Dorset a rival to anything in the country-house tradition, So timeless are its enclosures, its alleys and its 17th century style Wilderness that I half expected to meet Sir Francis Bacon stooping to sniff the roses. The Flowery Mead is the hardest idiom to perfect. To achieve it in perfection you must master meadows and marry them to the world of roses and peonies. You must starve the grass and bring in a banquet of wildflowers…. It was reassuring to know that there was a human agency in all this; someone drove a lorry with half the haycrop of Great Dixter to Dorset and spread it in the incipient mead.

The second modern Eden was at Petworth House, where Caroline Egremont has reimagined the appropriately vast walled gardens of one of England’s palaces. It was the setting for the museum’s second Garden Literary Festival. The first, at Tom and Sue Stuart-Smith’s garden near St Alban’s last year, was blessed with perfect June days – and so was the second. The pretty little marquees were called on only for shade from the sun of the longest day.

When you enter a garden through an orchard of apple trees smothered in roses that give them a second flowering, to follow long alleys of roses blending with clematis, to discover a dozen garden rooms of extraordinary variety, the ‘70s might never have happened. Gardeners have all the skills again. Everything seems possible. You marvel that anyone’s sense of scale and colour and texture can keep you keyed up, breathless for more. I’m afraid you can even start to take for granted the craftsmanship that realizes such ambitious plans. It all seems to be a dream. And the deer are gathering for the sunset over the lake. And 200 years ago Turner was here, painting this precise scene…. Yes, you can be carried away.

The talk that inspired me most, among a dozen teasing out the tangled themes of gardening and writers, and painters and their gardens, was Tom Stuart-Smith’s revelations of how a great designer plans his work. The interaction of place and personality (clients can be indecisive – or cussed), finding a graphic link between them that anchors the site, the values of contrast, concentration, contradiction. counterpoint, complexity, concealment… all sound very abstract. In this mesmerizing half-hour they seemed the necessary keys of creation. Gardening has brought out genius again, as it did when Kent and Brown and Repton were driving ideas.