The question becomes acute in summer: which would you rather have, a sunny garden or a shady one?

The majority view is understandably for sun. “South-facing garden” is a selling point. In town gardens you may have no choice. Our house is on the north side of an east-west street, the right house but the wrong garden? We had our doubts, but not any more – at least in summer, when it matters most. The summer sun starts the day peering over the eastern wall and finishes it beaming over the western one. The garden side of the house stays cool and the garden gets plenty of light. We are also blessed to have a tall tree in our neighbour’s garden to the west. We have dappled light on a sunny day in the centre of the garden.

Unfortunately the tree is a walnut, a beautiful dome of leaves on a smart grey trunk, but a hailstorm of green nuts in early summer and a constant rain of half-chewed half-ripe ones when the squirrels move in (they’re never far away).

As to plants in the shade, our predecessors took the view that box was the only thing. We are trying everything my favourite advisor, dear old Brigadier Lucas Phillips, advises. His Modern Flower Garden is never far from the top of my book heap despite being 45 years old.

The hydrangeas are just coming on, the blue ones from Saling that I christened Len Ratcliff after our benefactor have pride of place.: four big pots around the central (to use a grand term) piazza where we sit. The Brig says all campanulas tolerate shade. My favourite C. persicifolia certainly does. The pelargoniums in pots need promoting to the sunniest part at the far end. The roses on the walls (I don’t know all their names yet, but I know I don’t like Fragrant Cloud) are doing fine – high up above the wall. The scarlet Fuchsia boliviana, a standard in a pot, has been brilliant. Runner beans have been a disaster; being late I bought plants and failed to read the word dwarf (in dwarf type) on the label. So my poles are bare, with a few ludicrous plants at the bottom. What, I ask, is the point of a dwarf runner bean when the whole point is their climbing?

We’re experimenting with agapanthus. The plants we ordered at Chelsea have just arrived, with one flower bud each, seriously pot-bound. They’ve gone into deep gravel and old manure watered every night until they get going. Not everything is perfect. We don’t like a couple of the established roses (Fragrant Cloud is one); but how do you change them? Could one cut them down and bud onto the base? A Fuchsia magellanica has some lurgy that eats away its lower leaves, turning them brown – so presumably not a slug. There are lots of snails, but also the friendliest blackbirds and robin. Yes, on balance the shady life is a sweet one.

….. that was the title Tom Stuart-Smith gave to a Literary Festival organised by The Garden Museum in the Stuart-Smith’s garden last weekend.

The timing was propitious: only the second weekend this year when a festival in a garden had no need for umbrellas. Saturday was warm and partly sunny, Sunday was a proper summer day. We needed the shade of the tent for the lectures that were the centrepiece; a tent you discovered within beech hedges in the heart of a garden as lovely, and in as beautifully-timed perfection, as I could imagine. So beautifully-timed, in fact, that groups of flowers that had been in promisingly imminent bud on the first day showed their colours to the sun on the second.

The garden crests a modest ridge in a corner of Hertfordshire miraculously preserved from new towns and motorways, sheltering among its high hedges, then suddenly bursting out into a long view over fields and woods. There are few gardens these days where perennials hold sway: here not in conventional borders but in great plats thirty feet or so across and deep. Their early summer costume is predominantly cream and white and a dozen shades of purply blue; in one room shading into pale pink, in another into stronger yellows – but in gentle transitions that only dawn on you as you rest your eyes on the whole panorama.

The Festival unfolded in the same seamless way, moving from the fundamentals of garden philosophy to depths of practical experience, represented by Piet Oudolf, the blunt authoritative Dutch designer who has made the whole world plant grasses. (No grasses could be more beautiful, though, than the rippling filigree of the meadows round the garden we were in).

Christopher Woodward, the museum’s hyper-energized director, pursued the vision of Arcadia with Adam Nicholson – himself a practitioner of moving prose. Sue Stuart-Smith spoke with extraordinary insight on the therapeutic properties of gardening, Hugh Cavendish talked about Holker, his Cumbrian estate, Sarah Raven about Vita Sackville-West. Anna Pavord talked to John Sales, Penelope Hobhouse to Tom Stuart-Smith…. the cast was exceptional and there wasn’t time to hear them all.

There was music, there were oysters, when night fell the colours of the garden deepened and glowed and a slow river of pale smoke rose vertically from the barbecue fire. It was an ambitious event that succeeded to perfection. How lucky we were to be there.  The museum that does this deserves massive support.

The raw figures are not encouraging. We have swapped our country garden for a city one which is precisely one five-hundred-and-thirty-sixth of the size.  Twelve acres exchanged for just under one thousand square feet. It means a totally different relationship with your plants, a new regime, which could (strangely) become hectically intense, a change down into a very low gear indeed, needing frantic pedalling.

My night thoughts at Saling Hall wandered round the acres enjoying, or dissatisfied with, trees or groups of trees, concerned with blanket weed in a pond or when to cut some long grass. Spring (specially this year) unfolded week by week over a good three months. You could go off for a week without missing anything vital.

Here, in contrast, I will start awake at midnight with a brain wave: the shoot heading up the wall could be tied in a foot to the left; I could remove a couple of leaves to make room for that flower; the pot of lavender would get more sun on a higher step. It’s a hectic little microcosm, held artificially in some sort of equilibrium by constant

adjustments and daily doling out of water, dowsing one plant and letting another go thirsty to toughen it up.

I know the green fly (there are currently three) by name and take a magnifying glass to a spot of mildew. If anything gets out of hand, in other words, I have only myself to blame.

What does our little domain contain? We are still finding out. It has three levels, descending to the kitchen and the shady little patio outside it. The levels are important – and intriguing; the far quarter of the garden (the part that gets most sun) is raised up five steps, fenced off by a stone balustrade, in some ways looking like the poop deck of (shall we say) a frigate. It stands several feet higher than the surrounding gardens beyond its grey-brick walls. How this happened it’s hard to say, except that it was a long time ago; our massive sycamore grows at this level, and you can’t alter the ground level round a tree.

In any case the poop gives a good view back towards the back of the house, which in turn has a ground-floor balcony, so at each end there is a comprehensive view, as from a hill into a valley. (See, my delusions have started already). A relatively broad path leads up the centre, edged with box. Its stone matches the grey London brick of the walls. It widens in the centre to make room for a table, pots, a Mr Spit face splashing into a tiny basin. Whenever it was built (I suppose in the 1970s) it was done well, with good materials. The walls are trellised to nine feet or so and carry a green load of ivy, climbing hydrangeas, roses, honeysuckle and jasmine. It is a well-furnished box, into which I plan to pack all sorts of joys. We have ordered the greenhouse. There won’t be room to even tickle a cat.

After St Paul’s, Exbury the next weekend came as a complete contrast: a garden that shows off its astonishing collection of plants like a museum.

The Rothschild style (Exbury was largely the creation of Lionel de Rothschild in the 1920’s) is full-on; what J C London would have called “gardenesque”. If nature never made sylvan glades with smooth straight hedges, still less did it fill woods to the brim with a kaleidoscope of flowers of different species and varieties in the full spectrum of colours.

Both gardens, Exbury and St Paul’s, gain their dignity from their high vaults of towering trees – above all oaks – that moderate light and

temperature in their shade. St Paul’s is decorated with Augustan restraint; the confident simplicity of the Georgian  age. Exbury revels in the excitable showmanship of the Victorians. In fact the Rothschild style, indoors or out. You see it at Waddesdon Manor in the rich recipe of Gainsboroughs and Versailles furniture and the extravagant full-dress bedding of the parterres. In the New Forest it takes the form of a dazzling display of rhododendrons, azaleas, camellias and every flowering plant and tree that can be fitted in 220 acres of immaculate woodland – along with the smartest of miniature steam railways.

Perhaps its high point, for this romantic gardener, is where after a sustained passage of ravishing camellias the flower power moderates, the trees thin out, and glimpses of sparkling water allow you to see white sails gliding by. You are, after all, on the Beaulieu River, the Solent is round the corner, and there is that faint smell of salt in the air.

You see the plant you’ve been looking for growing lustily in a big pot in a nursery sales bed. You pay the 5-litre premium, you take it home, dig the hole, add the fertilizer, knock the plant out of the pot – and a meagre little root comes out in a cascade of fresh compost.

It happened to me again yesterday. The guilty nursery was Wisley. There should be a decent delay after repotting for plants to fill their pots again before they are offered for sale.

.....a green shade at St Paul's

To St Paul’s Walden Bury on one of the rare fine evenings of June to wander round one of England’s most romantic gardens at that moment when the very air seems charged with chlorophyll. It must have been on such an evening that Marvell wrote ‘a green thought in a green shade’. The oaks and ashes are joyfully green against an azure sky. Every plant is in improbable perfection; towering forest trees, magnolias in the infant innocence of pale flowers,  rhododendron of every hue, billowing white clouds of Siberian malus, ivory flowered dogwoods and wild service trees the size of oaks.

But this is a woodland garden disciplined by calm grass rides, arrow-straight, turning your steps towards a statue, a pavilion, a grassy theatre overlooking a simple fountain. At one moment lilies distract you, at another the perfume of azaleas: all the spring garden pleasures are there, all the more intense for the calming effect of geometry and proportion, measured out in straight beech hedges.

Behind it all are two indefatigable treasure-hunters, Sir Simon and Lady Caroline Bowes Lyon.  Laid out this evening on the billiard table in the house were a hundred fascinating photographs they had taken in the previous weeks in Bhutan, many of rhododendrons planted or to be planted in Hertfordshire. Such enterprise, such order, and such an evening are really the summit of gardening.

Some veterans persist

Each year we try to time a visit to our Welsh woods to see the bluebells in their glory – hopefully in concert with the blue rhododendron augustinii we have infiltrated among the beeches. Last weekend was almost the bluebell climax; they still had a little way to go. The rhododendrons, on the other hand, seem to be better at time-keeping: they were perhaps a week past their peak. We call them blue, but the colour of French lavender is a closer match.

The Snowdonia spring, our neighbours tell us, is three weeks late, or (seeing it in a positive light) three weeks longer than usual this year. It is the most beautiful ever : the sky is azure, the opening leaves of oak and beech olive, russet and that most tender green, scarcely shade the woodland floor where bluebells in millions and clumps of primroses compete with the fresh fronds of ferns. In damper shade the little white stars of wood sorrel are like timid wood anemones. Locals say there is a relationship between wood sorrel and copper – which rings a bell at Cae Gwian: a projected gold mine here in the 1840s (we still use the old grey stone building) turned out to hold nothing but copper after all. What flowers would gold has favoured?

The next valley to ours, running north-south down to the estuary of the Afon Mawdach, has been bought by the Woodland Trust. Its name is Cwm Mynach, the valley of the monks (of the Cistercian Cymer Abbey at Dolgellau).Its secluded meadows, hemmed in almost completely by steep hills and dominated by the cliffs of Diffwys, a 2000-footer, must have been some of the loveliest in Wales before the foresters arrived. The Woodland Trust is dedicated to restoring the ancient oak woodland now brutally invaded by conifers. They planted spruce, larch, douglas fir and the hideous (and useless) lodgepole pine under the oaks with the object of shading them to death. Often they succeeded, but veteran oaks still persist, and in the remaining open meadows show how magnificent such sessile oaks can be.

We started the rescue and restoration of our own oakwoods at Cae Gwian nearly 20 years ago now. It’s a long job, but hugely rewarding.

I was nervous about going back to Saling Hall. Our successor there is a man of action, and I knew he would waste no time before tackling his new project. But what I saw when I went back last week astonished me – and made me realise how long I had let things drift.

Judy and I had often talked about felling the long file of Lombardy poplars that flanked the front of the house, memorable trees (they were planted in the 1930s) that contained the front courtyard, separating it visually from the churchyard next door.

Last week they had gone. A loader was shifting their immense logs onto a pile bigger than a bus. The sense of light and air around the pink brick façade of the house was extraordinary. The rather gloomy presence of the towering trees was replaced by the broad green dome of a wild service tree I planted in the churchyard in 1973, looking in perfect harmony with the grey flint and gothic windows of the church. It was our predecessor, Lady Carlyle, who wanted to hide the churchyard from the bedroom window (so we were told). Her poplars had gradually become the main feature – and to see them gone gave me a gush of relief, delight…. feelings I could have experienced years ago if I had been more resolute.

‘The axe is my pencil’ said Humfry Repton. Knowing when to fell trees is as vital as knowing which ones to plant.

Not only the poplars are gone. Boring Lawson cypresses I should have condemned twenty years ago (but didn’t, on the pretext that there were shelter from the cold east wind) are there no more. Old pollard bat willows have gone from the moat (I’m not so convinced about these); a dozen old friends – or at least acquaintances – are piles of firewood. There is less muddle, and less mystery too. Over the years our gardens create their own untouchable auras. Nostalgia feeds on inertia and vice versa. Seeing radical change, and knowing it was necessary, is exciting, surprisingly emotional but hugely positive.