The secret  gardens: Every year thousands of green-fingered amateurs throw open their private gardens and invite the public in for a glimpse of their handiwork. Emma Townshend grabs a copy of 'The Yellow Book' and takes a peek

There are all sorts of beliefs about how to garden: when to prune, what to plant, what's tasteful woodland gardening and what's just a big old mess. But there are a few points upon which all gardeners agree - one of them being the value of The Yellow Book. If you've never bought one, it's the canary-coloured volume you see by the till in garden centres and small-town bookshops. In fact, once you notice it, you begin to realise it's sold all over the place.

The real value of the book is for snooping, because it's a giant list of mostly private gardens, thrown open to whoever can pay the admission (around £3). There's no other way to see most of these gardens, and the owners tend to participate on just one or two days of the year, when they think their greenery is at its best. There are two main good points to the National Gardens Scheme (NGS), as it's called. One is that all the money goes to charity - it's already funded an astonishing 127 Macmillan nurses. The other, more selfish, plus-point is the famous homemade teas. Not every garden offers one, but when you do find one that does, make sure you get there early, because they are generally very nice indeed.

My grandma always had a battered copy of The Yellow Book in her kitchen; I remember the smeary print used to come off all over your hands. But things have changed since then and the book of the 21st century is an altogether slicker affair. But even those prone to nostalgia will be impressed by the way it now allows you to search for gardens open on the actual day you fancy visiting. And this year, for the first time, gardens new to the scheme are given extra emphasis with a handy highlight box.

Another plus is the list at the back of the book detailing national collections. For the uninitiated, this means that you can go and look at the collection of someone who has tried to get as many different specimens growing as possible from one single genus. For those with other priorities, there's another list covering gardens that also do bed and breakfast. And a quick look at the website reveals that it has the ability to do sophisticated searches for specific garden features or designers.

Sophisticated it may be, but the earthy reality is that someone still has to get on with the actual gardening, and, with 3,500 gardens due to open at least one day this year, there's a lot of frantic preparation currently underway.

I spoke to Kathy Brown, who opens her Bedfordshire garden for one day on 24 June. She is a typical NGS gardener. The four-and-a-half-acre plot is gardened solely by Brown and her husband, although she gets help from fellow villagers for the teas, and for the organisation of the car park. And she still clearly gets a thrill from the delighted comments she gets from visitors.

But Brown is an old hand at the scheme, having received her ceremonial trowel for long service just this year. 'We had it on display in the conservatory last time we opened the garden,' she says, with a smile, 'but I'm not sure anyone really noticed.'

These days, the merits of Brown's garden are enough to gain her a place in the esteemed Good Gardens Guide (with a star), but she still has a special place in her heart for the NGS. 'It all started because we were trying to open the garden of an old people's home to the public to raise funds. And the inspector said no to that, but they wanted to look at my garden. They came round and immediately wanted us in the book. It gave us such a huge boost, because having people come and appreciate what you are doing just gives you such pleasure. I owe The Yellow Book a great debt, because it all goes back to that first visit.'

But The Yellow Book is not restricted to grandly perfect gardens. Last year, for example, the Short Lots allotments in Kew, Surrey, made their debut, opening for inspection under the scheme, with home-made teas served at the local church. And, in Bristol's Kensington Road, Grenville Johnson and Alan Elms open their garden, which may only be 20ft by 16ft but is filled with sculptural folly and stylish gesture. They typify a new breed of Yellow Book gardener, aiming for small-scale perfection in an urban setting and possibly giving many of us more relevant inspiration to take home. The Bristol garden only fits five people at a time, so it's essential to book an appointment.

Even when dragged to Yellow Book gardens as a child, I enjoyed the sense of occasion, as well as the iced cupcakes. Today, I just marvel at the sheer courage and energy of the gardeners. 'Of course I still get worried,' says Brown. 'On our February opening, it snowed, and I got up, and there was nowhere to park any cars, and you couldn't see any snowdrops or aconites.' I don't think I could stand the stress, I tell her. 'But then it rained, and melted the snow, and it worked out,' she laughs.

Well, I think it takes a special kind of person.

If you do one thing... admire your daffodils

Award yourself time in the garden without any jobs to do - wrap up warm, pull a chair out of the kitchen, take a book and a cup of tea, and spend 10 minutes with the sun on your face, in the company of the daffodils. Wordsworth was right, you know - the memory will return to you when you are feeling vacant or stressed, and fill you with pleasure.

For information on Kathy Brown's garden, go to www.kathybrownsgarden.homestead.com. The garden at Kensington Road is open by appointment only on 10 and 24 June, and 15 and 29 July; 'The Yellow Book' is available from www.ngs.org.uk, priced £7.99