The spy who loved magnolias. Does Peter Smithers' green-fingered guide still cut it?

Sir Peter Smithers, who wrote Adventures of a Gardener, is widely supposed to be the chief inspiration for Ian Fleming's famous Bond. The two met during the war when Fleming arranged Smithers' posting to the SIS office in Paris. When Paris fell, Smithers and Fleming between them commandeered the seven merchant ships that brought the last of the British refugees safely away from mainland France. Smithers himself got back to England in a Sunderland flying boat and while the Battle of Britain was being fought out above, masterminded an efficient net below, rounding up German spies as they landed.

Fleming rescued him from an unenviable posting as aide-de-camp to the Duke of Windsor in the Bahamas and instead got him a job as naval attaché in Washington. Tall, languid, elegant (and armed with a special pen that turned into a pistol – a gift from Fleming), Smithers became an expert in spreading disinformation through the cocktail party circuit. It's not the kind of life that most gardeners look back on when they stroll around their patch.

Bond never showed a sign that he knew a tulip from a tiger lily, but Smithers was a plantsman from the beginning. While still at school, he started a ledger in which he entered details of every plant he acquired. By the end of his life – he died four years ago, aged 92 – the ledger contained more than 32,000 entries. While covertly watching the movements of German subs in Central America, he collected palms for the herbarium at the Natural History Museum and made himself a garden at Cuernavaca in Mexico, packed with orchids and aroids. For the past 30 years of his life, he gardened at Vico Morcote above Lake Lugano in Switzerland. There, he specialised in magnolias and peonies, bred nerines, planted thousands of lilies. And towards the end of his life composed a list of "Principles for my Garden". Would the rest of us gardeners agree with them?

The first is: "It shall be a source of pleasure to the owner and his friends, not a burden and an anxiety". Yes, absolutely, though it is amazing how many causes for anxiety people find in their gardens: autumn leaves and their proper disposal should not be a subject to keep you awake at night.

No 2: "It must therefore be designed and planted so as to reduce labour to a minimum, and the amount of work involved must diminish as the owner grows older". Only someone approaching the last chapter of his gardening life would have added that codicil about work diminishing with age. When you first start to garden, you have no idea what labour will be involved in your design and planting. You just push on regardless. Then, gradually, you get so sucked into the whole business, that whatever you are doing – pruning, digging, weeding – doesn't seem onerous. The whole point is the process, not the product.

No 3: "All plants in the garden must be of a permanent character: no annuals, biennials or plants requiring lifting in winter or attention of a special kind. They must become a self-sustaining plant community, within which, as in nature, they support and maintain one another without the intervention of man". This is where it becomes even more obvious than it is in No 2 that there is no place in the Smithers garden for cabbages and salad crops. That's fine. But even in a garden that is purely ornamental, I'd still want to grow annuals and biennials. Among more permanent plantings, they provide change. And many annuals are self-sustaining, seeding about in different places, adding surprises. But I'm with him entirely on plants that need to be nursed from October until April. There is no pleasure in looking at a winter garden dressed overall in greying fleece.

No 4: "Fragrant and aromatic plants have preferential admission to add a fifth dimension to the garden: the fourth, of course, is time/motion". Yes. Scent is critical. Who'd plant a rose that didn't smell? During the bitter days of mid-November, the scent drifting from a pot of 'Double Roman' narcissus I'd brought indoors was a potent reminder of the pleasures that come with spring. For fragrance, Smithers would have been well served by his magnolias – M. denudata in spring, M. obovata with melon-smelling flowers in early summer, M. virginiana, the sweet bay, in late summer. Spring flowering M. x soulangeana, the magnolia you most commonly see in gardens, has practically no scent.

No 5: "Plants which flower early or late in the year, or in July, the green month, also have preference, to extend the flowering season". This is a very good principle. April, May and June look after themselves in a garden, partly because that's when we gardeners are most likely to charge into garden centres, and fall in love with things that are in flower. I'm still fighting the late summer recession.

Lilies, which Smithers loved, give a great boost in July, and for August, I mostly depend on various forms of Hydrangea villosa.

Until I got interested in this particular hydrangea, I had no idea how much it varied. Now I'm collecting different forms. The one I planted this spring was propagated by Michael Wickenden of Cally Gardens from a superb specimen that grows by his house. I hope it does as well with us.

No 6: "The planting must be of a dense kind, so that the plants live intimately together with little space for weeds to grow or need for support. The plants themselves must do the garden work". This principle is a fine one, but in practice it doesn't always work. For maximum effect, a garden ought to be built up in three tiers, trees on the top, shrubs in the middle, with bulbs and herbaceous stuff at the bottom. But things die, or grow more than you thought they would, shading out plants below. And I've never yet achieved plantings so dense that there's no need for weeding. Don't they have bindweed in Switzerland? But Smithers is right about planting things that don't need to be propped up. Staking is a bore and only works when it is invisible. Which is almost never.

No 7: "Difficult plants, if not successful after a fair trial, are abandoned for easier subjects of which there are plenty". Very wise. No gardener should kill the same plant more than three times. Some, of course, live for the fact that they are growing a plant that everyone else they know has failed with. But it is nerve-wracking to wander around a garden where everything is a "treasure" fenced off with sticks, covered with a cloche, ill at ease in its surroundings. You can only feel comfortable in a garden where the plants are comfortable, too. And this principle means I will never have to lie awake worrying about the fate of Fritillaria alfredae subsp. glaucoviridis. Which takes care of principle one, as well. Result!