Avant gardening: Discovers the beauty of glass shards and broken plant pots

Emma Townshend meets the author of a new book celebrating the contentious work of the avant gardeners

Living wall: Emma and Tim Richardson in London's New Street Square © Teena Taylor

"This building is so interesting, with the dark green of the plants against the silver," says Tim Richardson, pointing up.

I'm at the City of London's first "green wall" development, in New Street Square, with Richardson, who is gardens editor of Country Life. He is a passionate enthusiast of the 18th century – "Alexander Pope and so on", he laughs – and has made a 20-year study of the landscape garden, published last year as Arcadian Friends (out now in Bantam Press paperback at £14.99).

It raises the question of why we are in New Street Square, which is hardly Arcadian. The answer is that Richardson is one of the few garden historians who combines a passion for the old with delight in the new: four years as landscape editor for the trend-spotting glossy Wallpaper saw him develop a love for the kind of gardens that make some little old ladies feel sick.

"In fact, it's amazing quite how angry people get at these modern gardens – as if you're trying to destroy innocence itself," he says. So what exactly is turning garden reactionaries blue in the face? You can see for yourself in Richardson's new book, Avant Gardeners (Thames and Hudson, £24.95), which is devoted to what he calls "conceptualist" garden design. A garden of glass shards in San Francisco; broken plant pots in a tribute to illegal Mexican agricultural workers; even gardens, dare I say it, with no plants at all.

The trouble started with Martha Schwartz, who in 1979 spent weeks up in her attic varnishing pastries to make her Bagel Garden – a front garden which is planted with bagels. It sounds like a joke, but it was serious enough that the editor of Landscape Architecture, who dared to feature the work on the cover, ended up getting the sack. Think of the Bagel Garden as the horticultural world's shark in formaldehyde and you are along the right lines. Today, Schwartz is world-famous: her work is the centrepiece of Dublin's new Grand Canal Square scheme.

Yet, almost 30 years after Schwartz's bready beginnings, conceptual gardening still manages to shock. When Hampton Court Flower Show introduced a special show-garden category for conceptual gardens, there was uproar.

For those of us who actually like this stuff, Richardson's book is a godsend. Inspiring, playful and serious by turns, these gardens challenge our thinking in the same way as high art. Whether documenting massive earthworks influenced by land artists such as Robert Smithson, or Tony Heywood's inner-city, council-estate fantasias, Avant Gardeners is the future's essential gazetteer. n

Broaden your horizons: Conceptual landmarks

Swiss Cottage Open Space, London (2006)

Gustafson Porter is more famous for the Diana Fountain on Hyde Park, but this square, tucked away behind a thoroughfare, is simple and peaceful

Birmingham Bullring (2003)

GrossMax created a landscape to match the flagship Selfridges store, with coloured-water sculpture and "lightwands", as well as gentle terracing

Face of Liverpool (2005)

The sculptor Stephen Broadbent has created a garden loosely based around the theme of immigration to Liverpool. The Face of Liverpool, on the site of St Paul's Eye Hospital, was created to evoke the spirit of travel and adventure

Read Emma Townshend's new column at blogs.independent.co.uk/independent/a_nice_green_leaf