How to sneak a peek over the garden fence

The National Gardens Scheme, 85 years old this year, offers the chance to be nosey in a good cause, reports Victoria Summerley

Picture the scene. The sun is shining and the fragrance of roses, lavender and new-mown grass hangs in the air. In the distance you can hear the clink of tea cups and the sound of chatter as visitors try to choose between lemon drizzle and coffee and walnut cake.

Click HERE to to sneak a peek

Some sit in solitary silence, drinking in the scents and sounds of an English garden in summer. Others compare notes ("My wisteria's got loads more flowers than that!") or scribble down the names of choice varieties that have caught their eye. Small children inspect ponds for fish or investigate the water feature under the watchful eye of their parents. It's a typical National Gardens Scheme (NGS) open day.

I open my London garden for the NGS in August, for the fifth year running, so I can say from personal experience that this picture is no fantasy. Generally, the weather has been reasonably good. Visitors are, on the whole, charming. And the coffee cake always goes down well.

Easter traditionally marks the start of the gardening season and the NGS , which celebrates its 85th anniversary this year, offers a fantastic way to see gardens that – short of climbing over the wall – you would never normally be able to enter. Indeed, a friend says that where she lives, just outside Oxford, an NGS opening is known as Nosy Neighbour Day, because it's such a good opportunity to have a gander at a property you've always wanted to see.

If you've just moved into an area, and want the lowdown on the local allotments, or the best garden centre, or you need to find someone to put up a shed, make a beeline for your nearest NGS garden. Owners are usually happy to share information and gossip about local life – and they'll offer practical advice about the local soil conditions and what will do well in your garden.

You can find an NGS garden open somewhere in England and Wales (Scotland has its own scheme) from February (snowdrops) through to Christmas. There are famous gardens, such as Sissinghurst, created by Vita Sackville-West, and Great Dixter, the home of Christopher Lloyd. There are grand gardens – Hatfield House, and Highclere, the location for Downton Abbey. Even the Queen and the Archbishop of Canterbury get in on the act, opening the Frogmore House gardens at Windsor, and the gardens at Lambeth Palace.

There are allotments, and bluebell woods, and rhododendron walks, and sub-tropical gardens like mine, which take advantage of London's urban heat island effect. Best of all for the domestic gardener, there are smaller gardens full of ideas that might suit your own.

Garden visiting is not a modern phenomenon, as a new exhibition opening later this month at the Garden Museum in Lambeth, south London, will tell you. Timed to coincide with the NGS 85th anniversary, it looks at how artists recorded the great gardens of their day and laid the foundations for tourism.

But what is it for, the NGS, apart from allowing people to have a nice afternoon. The National Gardens Scheme was funded in 1927, to raise money for the Queen's Nursing Institute. More than 600 garden owners opened their gates in the first year, including Sandringham, and Arundel, Scotney and Sudeley Castles. By 1931, the number of gardens in the scheme had grown to more than 1,000. This year, more than 3,800 gardens will open, including 120 of what are now known as the "1927 gardens". The NGS expects to raise more than £2.5m in 2012.

The money is donated primarily to charities offering nursing and palliative care, such as Macmillan Cancer Support and Marie Curie. Indeed, the NGS is Macmillan's largest single donor.

There is a fairly rigorous selection procedure for the Yellow Book. The NGS wants to ensure the public gets value for money, and also wants to know there are no hazards – so slippery steps and bridges without handrails are a no-no.

Most garden owners will tell you that their inspection ranks as one of the most terrifying experiences of their life. It goes without saying the garden has to be of a certain standard, and it must provide – in the infamous NGS phrase – "45 minutes of interest".

So if you are garden visiting over the next few weeks, spare a thought for the owner, who has been alternately weeding and baking for the past few frantic days. More coffee cake, anyone?

Sowing the seeds: How it all began

Eighty-five years ago, Miss Elsie Wagg, the sister of a successful financier, came up with the idea of opening private gardens to the public to raise funds for the Queen's Nursing Institute. Miss Wagg, whose portrait was painted by John Singer Sargent, realised her wealthy friends might enjoy showing off their manicured lawns and herbaceous borders to an admiring public. Her idea had far-reaching repercussions: as well as raising money, it democratised garden visiting. For the first time, ordinary people could stroll through the gates of some of the grandest houses in the land on payment of just one shilling (5p). They didn't have to wait to be invited – and they didn't have to tug their forelocks.