Now the good news: it's turning out gloriously for Chelsea

After years in the doldrums, Britain's best known flower show is emphatically back in fashion. Victoria Summerley celebrates

The Chelsea Flower Show opens today, the signal that the British summer is here, that the London Season has begun (if one cares about such things) and that at least 2,000 bottles of champagne and 47,000 glasses of Pimms are about to be downed by 157,000 visitors.

Tickets for Chelsea sold out days ago – a record, despite one of the worst winters in living memory. So what is the allure?

Well, there's the timing for a start. Just before half-term and at the end of the spring, a sunny Chelsea puts everyone in a summery mood. Temperatures yesterday were 27.4C, though it is forecast to cool down a bit by the end of the week.

There's also the horticultural excellence. Other gardening shows may be bigger or open for longer, but Chelsea is a world-beater both in terms of the standard and variety of exhibits. (You can blame Britain's colonial past for some of that.)

There are displays at Chelsea this year from Sri Lanka, Thailand, Malaysia, Grenada, Barbados, South Africa, France, Taiwan, Australia, Holland and Japan, all of which will guarantee coverage back home. That's why it's a favourite place to launch new plants – nearly 600 in the past eight years.

The social side is pretty A-list too. Royalty of all varieties – rock, fashion, film, theatre, television and even those people who live in Buckingham Palace – turn out to admire the show gardens, indulge a passion for ride-on mowers or simply have their photographs taken and sign autographs.

Flower power is the phrase that comes to mind. There's definitely something a bit Sixties about Chelsea, especially on press day, when celebs turn out in their dozens. It's as if one of the botanists had put some mind-altering substance into the buck's fizz, thus engendering a series of incongruous visions.

The press day was typical. In one corner there was Jamie Oliver cooking pizza in the Children's Society teenage garden. Right across from him, to the sound of deafening classical music, a bronzed naked dancer (well, apart from a thong) was making her sinuous way across the Foreign and Colonial Investments Garden, designed by Thomas Hoblyn.

There was a flurry of excitement when word went round that punk poet John Cooper Clarke was about to make an appearance and in another corner, scientist Stephen Hawking was launching the Motor Neurone Disease Association garden.

In a strangely surreal moment of art imitating life imitating art, actress Pam Ferris, one of the stars of the gardening whodunnit Rosemary and Thyme could be seen gazing thoughtfully at a water garden display in the Pavilion.

Like all British institutions, Chelsea has its traditions, however. The judging features groups of men in panama hats (and some women, sometimes also in panama hats) called things like Woody Plants Committee, with a show of hands determining who gets a gold medal.

Between 7 and 8 this morning, RHS officials will have gone round all the show gardens and Pavilion exhibits with the medal certificates – gold, silver-gilt, silver and bronze. It's quite rare that no award is given; a notable exception was James May's Plasticine garden last year – but even he got a Plasticine medal.

It's all very polite, all very low-key. Britain may have gardening talent, but it doesn't do anything so vulgar as shout about it – although, since Piers Morgan was also at press day, that may be about to change.

On Saturday, the final day, a bell is rung at 4pm to signal the start of Break-Down, a cross between Harrods' sale and a rugby scrum, in which ladies in floral dresses elbow each other out of the way in order to buy the plants being sold off from the show gardens at knock-down prices.

As the exhibitors start to dismantle their stands, a veritable forest of people with their perilous cargoes of waving delphiniums, roses and foxgloves will make its way to Sloane Square Tube station and another Chelsea Flower Show will be over.