Chelsea Fringe 2012: Tom Turner's journey People don't know about our garden heritage but it's a really important part of London's status as a cultural capital. I moved here in 1973 and it's taken me years to find out everything. I've written books and websites; the map is another way of telling the story. I want to give an overview, to show people what's been done before and what's possible in the future. My favourite section of the walk is the first part. It's the most historically interesting. So that, of course, is the part we will do. Victoria Tower Gardens seems a good place to start a London landscape walk, framed as it is by the Houses of Parliament and the River Thames. The big old plane trees are just coming into leaf and are slick with rain. We cross Millbank and head down some steps to the Jewel Tower and a scrap of sunken lawn in the shadow of Westminster Abbey. Tom hands me a garden style spotters" guide, which is a bit like a bird ID chart but for landscape design (you can find it at gardenvisit.com). It turns out we're standing in an example of a castle garden dating back to the 1300s. He explains that in medieval times this would have been home to flowers and food plants rather than mown grass. We walk on, past queues of tourists waiting to get into Westminster Abbey, and head around the back. It's possible to get in free if you're just looking at the cloisters. This is point three on the map, according to the display on my phone. The Small Cloister is a well-kept secret. It's beautifully planted with delicate pale silvers and greens. Close by is the College Garden, a bigger space with trees heavy with pink blossom. The wind has whipped up the blooms and the paths are painted with slippery petals. A medieval-style herb garden has appeared here since his last visit and Tom is delighted. It's not quite right but much better than it was. I start to learn that Tom, a stickler for historical accuracy, is quite hard to please. We pass the plain lawn of the Great Cloister on the way out. "How boring," he declares. It should be a meadow. Next stop on the map is Whitehall and another dull patch of lawn with a fascinating past. This stretch of road was once the site of Whitehall Palace and the grass outside the Ministry of Defence is a faint hint at a privy garden that belonged to Henry VIII. We race ahead through history to Duck Island Cottage on the edge of St James's Park. It's a storybook building surrounded by flower beds like brush strokes in the Arts and Crafts style. Looking at the online map, I discover that Duck Island dates from the 17th century, when St James's was the deer park for Whitehall Palace. The cottage was built in the 19th century in the style of a cottage ornée, and was given an Arts and Crafts cottage garden in the 20th - a symbol of England's peasant culture in the heart of the government quarter. "My grandfather used to buy fresh milk from a cow stationed in St James's Park," says Tom, which sets him dreaming aloud of a day when the cows return - perhaps to celebrate a future Chelsea Fringe. I asked him why he thinks London needs a new garden festival? The things that are outside the mainstream often become the most interesting and memorable. I'm originally from Edinburgh - I find the official festival rather dull but the Fringe is wonderful and far more fun. All sorts of surprises are possible. I love the Chelsea Flower Show. It's a bit like a reunion, as lots of my students from the University of Greenwich have shown there. But it's always been a regret of mine that the gardens are destroyed. There could be a longer-lasting, urban regeneration element to the Chelsea Fringe. It's a way of showing what London's future could be. The Fringe should be many things, but part of it should be political and an argument for change - instead of creating pamphlets, we'll create gardens. We talk about urban greening and Tom's excitement about possibilities for the future, such as living roofs and walls. He believes the new landscape style to add to his spotters" guide will be called the "sustainable style," and that gardens should help shape urban design. The conversation then turns to park management. Tom believes that standards of care have improved massively since the Nineties, but that there's a long way to go. Gardens are works of art, artefacts. In the Fifties there were very few garden historians, now there are quite a lot. But park management hasn't caught up. There's an avenue of sweet chestnuts in Greenwich Park that's the oldest of its kind in Britain, but the Royal Parks have built a bin store that blocks it. It displays an extraordinary level of artistic and historical ignorance putting it there. Defeated by time and weather, we fast-forward to the final dot on the 20‑mile garden route, Trafalgar Square. According to the map, is conceptually a terrace with the layout of a 19th-century landscape garden. The map explains that it was designed by Charles Barry, who also designed Italianate terraces for several Victorian gardens. Tom leaves me soggy but satiated with new knowledge, looking out over one of London's biggest tourist traps. It's a place decidedly devoid of green that has been given new life by the map. For Tom, understanding the past is an important way of coming up with ideas for the future, and that's what he hopes his walk through history will encourage people to do. How it works The London Gardens Walk is a free interactive online map, which you can access on a computer or on a smart phone via gardenvisit.com. It plots out the route from A to B, with information attached to each point on the map that you can read as you wander. There are 40 points of interest, and the walk follows a long loop that finishes almost where it begins in central London. A more comprehensive e-book guide will be on offer as a free download on May 19 and 20, the first weekend of the Chelsea Fringe. Chelsea Fringe highlights The Oranges and Lemons Garden by Daniel Shea will see the Spitalfields church St Leonard's of nursery rhyme fame, all hung about with citrus fruit. An old slaughter house in Clerkenwell is to be transformed into a Garden of Disorientation by Deborah Nagan. Three vertical garden towers planted with perennials are set to spring up in the grounds of the Garden Museum in Lambeth, London SE1. Angela Newman is designing an odoriferous medieval herb garden for the Idler Academy on Westbourne Park Road. Visitors are invited to help build a greenhouse out of plastic bottles at the Fern Street Community Garden in Mile End. Dalston will be getting its first flower show, with launch events at the Eastern Curve Garden. The Hogarth Roundabout in Chiswick will be transformed into a meadow. An Aromatic Herbs Mobile will appear in the grounds of the Geffrye Museum on Kingsland Road. The Dock Garden Festival in Ladbroke Grove promises an eclectic mix of happenings, including growing and cooking workshops. You can find more events listed at chelseafringe.com.