The road home from North Wales leads us through Welshpool, and often to the hanging gardens of Powys Castle, plunging terraces where the National Trust gardens in its grand manner to wonderful effect.

The other side of Welshpool, and unknown to us until recently, lies The Dingle, almost equally steep but markedly different in concept. The Joseph family started the nursery in the 1960s: the precipitous garden is where Barbara Joseph set out their wares. If the
emblem of Powys Castle is the baroque lead statues on the top terrace, The Dingle’s emblem is the washing-line across the upper lawn. This is domestic gardening you can do at home. I am certain the richness of planting packed around the steep paths has inspired thousands.

The theme on the high south-facing bank is permanent ground cover in high colour and maximum variety. Without level

terraces cultivation is tricky: most of the
plants here will fend for themselves. It is a style of gardening I associate with the southwest, in which evergreens and grasses play a large part, and the evergreens (hebes are important) are often clipped, sometimes draped with clematis.
A colour theme set up by, say, a red
rose is followed by plants of the same
colour in a tight group, then red leaves
followed by grey or gold. It is the way
many of us instinctively garden, applied
with consistent conviction to a whole hillside, and at the bottom to a broad pond. Maples and hydrangeas, dogwoods and bamboos spread over the facing slope: an arboretum on a domestic scale. Whatever the opposite of the grand
manner may be, The Dingle does it. Gardening could hardly be less threatening and more fun.

I’m not guilty of planning it this way, but ghastly good taste has broken out again in our borders this summer. Could I really have chosen such Mabel Lucy Atwell colours? It must be my inner little girl outing herself: there is nothing to disturb a dormouse in their almost inaudible harmonies. Goodness, I like it, though.

It is all pink, white and blue. The pinks are pale phlox, Japanese anemones, roses ‘Felicia’ and ‘Comte de Chambord’. Only slightly more assertive are Penstemon ‘Garnet’ and Salvia involucrata ‘Bethellii’. The blues run from Agapanthus and Salvia patens (its sapphire almost the only sharp note in the border) to somnolent blue rue, the azure
pinpricks of Salvia uliginosa and the purple exclamation marks of
Thalictrum dipterocarpum and Verbena bonariensis.

As for the whites, Phlox paniculata ‘White Admiral’ is in stratocumulus
mode after all the rain,‘Iceberg’ roses are glacial, cleomes are threatening arachnids and cosmos becoming shrubs. There is
shape and variety: tall spires of cool Veronicastrum and plump creamy ones of Kniphofia ‘Little Maid’, a low tangle of Aster divaricatus – white daisies on black stems. Later, fire will break out with sedums and crocosmias, chrysanthemums and turning leaves. Just now it reminds me of Katherine Hepburn’s acting, which
scanned, they said, the whole gamut of emotions from A to B. For the moment I’m extremely happy with A.

IT HAS BEEN LIKE GARDENING in another country these last two months. We had a typical year’s total rainfall by mid July. The garden is not complaining; on the contrary, new plants have established themselves in record time and old ones put on at least two years-worth
of growth. I have trouble finding where some of our paths have gone.

Oaks put on what are known as lammas shoots every tear, conspicuously reddish in many cases. Lammas means ‘Loaf mass’, the harvest festival once held on 1 August. Without waiting for August,
though, almost every plant has new shoots without precedent, the most intriguing being a Canadian red maple,Acer rubrum, which would much prefer an acid soil, apparently in flower, with long shoots starting chlorotically pale, then tipped with red leaves like red hot pokers against the sky.

Pity the poor city gardener, who has to cut off most of this lushness and bag it through the house to an authorised tip.

We tell our friends it is not really a garden at all, because when they find out that we tend a plot around a defunct goldmine in Snowdonia they all say ‘How can you possibly garden in two places at once?’ It’s better than counting sheep is my response.

It is only a sketch of a garden, in any case – but to me all the better for it. It lies by a stream in the middle of a wood, deep among thriving oak, ash and birch, with a distant view of that most noble of
rather short mountains, Cader Idris. Wales had its gold rush at much the same time as California and Australia, in the middle of the 19th century. The Cae Gwian mine was floated on the London Stock Exchange. Shafts were dug, railways installed and a crushing-mill

built, powered by a towering water wheel. All they fetched out in the end was copper, but the grey stone buildings stood – and 150 years later motivated our

garden, round the stream that runs from the mine-mouth, our deep dark grotto.

The old mine office, gabled but roofless, is the sheep-proof part for precious plants. The rest is defined only with low stone walls. One roofless shed is home to a hydrangea that fills it to overflowing

with deep bluey purple blooms. A

gunnera guards the path up to the grotto. Embothriums stand round it like flaming brands. Strawberry trees stand at the corners. There is a graceful myrtle gleaned as a seedling from a Scottish forest, a maiten from Patagonia, and ferns ranging from the Royal, one day I hope in these conditions the size of a small tractor, to the e xquisite little thing with two inch fronds that grows between the dark grey stones. In such acid soil with 70 inches of rain a year things become possible that in Essex are out of the question.

I lean on clematis in summer like a drunk on the bottle. They seem to be doing half the work of keeping a sparkle in the
surging masses of green, a handful that time has shown keep producing wonderful colour week after week. Of all the midsummer ones C. ‘Perle d’Azur’ is queen, climbing, spreading, drooping and generally distributing its pale violet-blue flowers, individuals that tilt this way and that, catching different lights. It wanders up my favourite climbing rose, the buff/
white/pink R. ‘Alister Stella Gray’ and dances over my favourite white/ pink/red hydrangea, H. serrata‘Grayswood’.

At the same time Clematis x durandiitakes care of the deep blue end of the spectrum – with less elegance but equal generosity. C. x durandii has no means of climbing, but we have made it brushwood wigwams in beds where perennials crowd around. Alstromeria ligtu is the perfect pink to set one off. Buff plumes of Macleaya cordata and
blue spikes of delphiniums jostle round another.

The only clematis in the garden when we arrived was C. ‘Alba Luxurians’. The second name is apt, the first less so: flowers can be white or green, and are usually harlequins of the two. It belongs to the later-flowering and smaller- flowered category that go under the general heading viticella. I scarcely mind which of this featherweight tribe I grow:
their casual little flowers pour off the vine from June to September. C. ‘Kermesina’
is like velvet wine, ‘Minuet’ a merry muddle of purple and white, ‘Polish Spirit’ close to C. x durandii,
‘Madame Julia Correvon’ more red wine, but with narrow petals widely spaced. All these grow here with blithe good humour.

A plantsman is as hard to define as he (or she) is easy to recognise. His (or her) garden is easy to recognise, too: a place where plants subtly out of the ordinary form a thriving community. Where the rare, the newly-discovered and the élite of the plant world are cherished with passion (and where there is never room to
accommodate all the newcomers).

We went to such a garden the other day: White House Farm on the Kentish Downs, the creation of Maurice and RosemaryFoster. It was a journey through layers of discovery: from smiling lawn through classic pergola into a forest of flowers where all horticultural
inhibitions have been thrown away. Up every tree clambers a rose, and up each rose a vine. Clematis scrambles through magnolia, Actinidia through Azalea, and the earth below and between is pulsing with competing growth. The pergola snakes for 100 yards among maples and bamboos, rhodendrons and roses, dripping with every wisteria known to man. Seven more acres of arboretum are
planted with trees from wild-collected seed. If plantsmanship like this is exhausting to view what must it be like to practice? To judge by the Fosters’ purposeful serenity, pretty close to heaven.

Those prone to nervous anxiety should stay away from the July issue of the Quarterly Journal of Forestry. It describes a new disease affecting gardens in Cornwall. What is known in America as Sudden Oak Death has been flagged as a threat here for the past five years. The new find is another strain of Phytophthora all too well adapted to
destroying Cornwall’s precious trees and shrubs.

Phytophthora kernoviae takes its name from Kernow, the old name for Cornwall. It loves Cornwall’s jungle conditions where big-leaved rhododendrons and magnolias thrive, spreading through mist and water-drops where breezes rarely stir. Eighty Cornish gardens have so far been infected, among them Trengwainton, where the National Trust has set up a monitoring station. Phytophthora there has already claimed magnolias, acacia, jasmines, rhododendrons and kalmias. In
other gardens camellias, viburnums and drimys have caught it. Worse, there are cases of beech (but not oak) being affected. Given the right conditions Phytophthora of two strains – kernoviae and the original Sudden Oak Death strain, ramorum – seem able to kill almost anything.

The conditions are specific, and rhododendrons are important hosts. R. ponticum, that ineradicable weed (however pretty its flowers) of broadleaved woodlands, harbours Phytophthora and passes it on. The precautions to take are to reduce the damp shade element, clearing undergrowth to let light and air in, to get rid of weak old wood and promote strong growth. Bleeding bark cankers are the
principal symptoms. None of it makes pretty reading.

With this year’s weather I had just been relishing the almost Cornish feel (at least for an Essex garden) of our establishing
woodland, the damp mulch and the dense foliage. For how much longer, I wonder.

‘TIME’, SAID SOME PHILOSOPHICAL WAG,‘is nature’s way of stopping everything from happening at once.’ Until this spring, that
was, when something went wrong with the mechanism. A month of near-summer weather, and not a drop of rain in six weeks, had this garden (and certainly this gardener) seriously disoriented. Tulips and roses together upset my sense of propriety, not to mention colour. Fauve is the word for the cerise of Rosa ‘Zéphirine Drouhin’, the red of a tulip called ‘Bastogne’ and the bright amber-brown of my favourite wallflower.“Go back in and wait your turn,” I said to the rose. But no.

After six weeks the rain came reluctantly, unable to cure the chapped and ravined clay. Rabbits could still get their paws trapped in the cracks. At one point you felt horses had better watch where they
put their hooves. Don’t think I’m complaining. Blossom has never been more bountiful, nor early May a more sensuous moment. When hawthorn fills the hedges round magnolias in voluptuous bloom all is well. I have been going out daily at dusk to marvel at the Staphylea colchica I grew from one of the seeds in a purloined ‘bladder’ years
ago. Bladdernut is the purportedly common name of this estimable bush, now 15 feet high and weighed down with intricate bunches of white flowers. Poppable green bladders follow. Dusk is its moment (it is for all white flowers) because then, I have discovered, it transmits to the maximum its creamy gardenia smell. I didn’t know anything else could do gardenia.

The colour theme now is searing spurge green. Did I intend euphorbias to take over? You might think so: a chlorophyll surge has that effect. Brightest of all

spurges is Euphorbia palustris – which

also offers orange leaves in autumn. Box hedges join in as they put on new

Staphylea colchica’s gardenia-like growth, and I seem to have let the

brilliant green Alexanders (Smyrnium
perfoliatum) get out of hand again. Two years ago 300 volunteers were needed to scour Kew of this menace to the luebells. Perhaps we should put it back on the menu, as it was before we had celery.