Starting today, and for the rest of the week, the sound of tramping feet shod in sensible shoes will reverberate through the streets around Sloane Square as 157,000 of Britain's keenest gardeners make their way to the grounds of the Royal Hospital for the Royal Horticultural Society's Chelsea Flower Show.
Fortunately, the weather forecast is good, but even if it wasn't, they'd still come, because for gardeners, Chelsea is the Cup Final, the Grand National, the Last Night of the Proms, Wimbledon and the Lord's Test match all rolled into one. Other flower shows may claim to be bigger, but Chelsea has a truly international prestige of which British gardeners are secretly rather proud.
This dimension is rather appropriate, of course, because although we British like to think we have a monopoly on horticultural expertise, we've been nicking our inspiration and ideas - not to mention plants - from around the world since the Romans built the first examples of patios and hot tubs on British soil back in 55BC. (They didn't do decking: Julius Caesar may have crossed the Rubicon, but he obviously knew where to draw the line when it came to garden design.)
The idea of a walled enclosure filled with flowers and perhaps a fountain or murmuring rill, which we think of as quintessentially English, is central to the Moghul tradition, brought to the West via the Crusades and the Moorish invasion of Spain.
From Scheherazade's sumptuous descriptions of gardens planted with lilies, and vines laden with grapes like rubies in the Arabian Nights to, say, Frances Hodgson Burnett's account of the healing power of horticulture in The Secret Garden, may seem a long way, in terms of geography and literary tradition, but on the heartstrings of any gardener, they will both strike exactly the same chord.
You probably won't find Scheherazade's couches of silver and sandalwood or pots of inlaid gold at Chelsea this year. But you will find that sense of stepping into something that is magical. The show gardens, created in only four weeks, spring up like mushrooms, crammed with plants that flower at just the right moment, as if orchestrated by some sort of sorcery. In the Great Pavilion, the nurserymen and women have been employing their dark arts, too; coaxing agapanthus into bloom two months early, cosseting iris with wads of strategically placed cotton wool or touching up the farinaceous, fan-shaped fronds of a Bismarck palm with face powder. Instant impact? Well, yes and no.
The phrase "instant impact" has become a little tarnished in recent years. Traditionalists mutter darkly about neighbours who fling down some hard landscaping (or the dreaded decking), chuck a couple of (expensive) tubs of (even more expensive) bamboo on top of it and sit back and admire the view from the comfort of their (extremely expensive) sunloungers.
I've nothing against instant impact. Any impact is better than none at all, and if spending £100 on some vast palm is going to get Mr and Mrs Johnny Come-Lately into gardening, then I'm all for it. These days we all move around a lot more, we all work harder and fewer of us are lucky enough to be able to sit and watch a garden mature for 20 years.
However, Chelsea wouldn't be Chelsea unless it was firmly underpinned by extraordinary levels of skill. And in the same way, I think that if we lost the habit of growing our own plants or putting our hands anywhere near the soil altogether, we would also lose that emotional connection that binds us to the land and makes us care about how it looks and what will happen to it in the future.
The gardening writer Ursula Buchan told me at the Chelsea press launch yesterday that this year's show - the 32nd that she has attended - has been the most exciting of all because she had been working on the Transit of Venus show garden, built by her old college, New Hall, Cambridge. Exhausted by having worked until dusk the previous evening, she was nonetheless exhilarated by being part of the process of creation, rather than a mere observer.
It was a feeling Vita Sackville-West, one of the greatest British gardeners, would have recognised. She once took one of her readers to task for suggesting that she was an armchair gardener who lacked any practical skills. "For the last 40 years of my life," she blazed, "I have broken my back, my fingernails, and sometimes my heart, in the practical pursuit of my favourite occupation."
Scratch the surface of the newly planted borders at Chelsea and you'll find quite a few back problems and broken finger-nails and the odd little piece of broken heart. They're part of the mulch that makes those seemingly effortless gardens and glorious flowers look so good.