Photo: Al Pasternak

They work under the cover of night, armed with seed bombs, chemical weapons and pitchforks.

Their tactics are anarchistic, their attitude revolutionary. Their aim: to beautify.

An army of self-styled "guerrilla gardeners" is growing across the world, fighting to transform urban wastelands into horticultural havens from London and Tokyo to Montreal and Vancouver — where global group number 56, the Vancouver Guerrilla Gardening Meetup Group, boasts nearly 200 members.

"We will be planting derelict sites, and developing ideas about provoking ecological/cultural insights through plant art," reads the opening comments on the group’s web-based bulletin board.

"Guerrilla Gardening is a lot like good grafitti on a bland wall, only our mediums are seeds, soil and nature!"

To document and encourage their victories, one of the international movement’s top generals has written a handbook.

On Guerrilla Gardening by Richard Reynolds, defines the activity as "the illicit cultivation of someone else’s land."

"Our main enemies are neglect and scarcity of land," said Reynolds, a 30-year-old former advertising employee.

He wrote the book after his website guerrillagardening.org became a global focal point for would-be green-fingered activists.

"Land is a finite resource — and yet areas like this are not being used. That seems crazy to me.

"And if the authorities want to get in the way of that logic, then we will fight them — but peacefully — through showing them what we can achieve with plants."

As he spoke, Reynolds and several London-based troops were enthusiastically digging over soil in a rough patch of grass outside a tower block in the south east of the capital.

Defying darkness — and risking arrest for criminal damage — they continued their "attack" on the otherwise grim, grey surroundings, forking in a hefty load of compost and planting lavender and Paris daisies for a splash of colour and scent.

Thousands of "troops" worldwide have signed up to Reynolds’ website — each has his or her own troop number — where they post reports and pictures of their battles, or "troop digs."

For those inspired to follow suit, Reynolds’ book outlines tips and advice on everything from the most suitable clothing and what kind of lighting and communication equipment to use, to how to carry out a "seed bombing" raid.

"Scattering seeds is the easiest way to guerrilla gardening," he writes.

"You do not even have to stop moving to do it — GG (Guerrilla Gardener) 830 Tony releases handfuls of Welsh poppy seeds while driving along the M60 motorway."

Reynolds says he was inspired to write the book after his first nocturnal gardening experience outside his own 1970s concrete tower block in London, when he discovered he was part of a largely secret but worldwide movement.

"I began because I moved to a tower block and had no garden, and yet all around me there were bits of land that nobody was looking after — so I have made it into my own garden. But it’s that one everyone shares and can get involved in," he said.

"I stepped out into the world to cultivate land wherever I liked.

"The mission was to fight the miserable public flowerbeds around my neighbourhood."

The book charts what it says is a "revolutionary history" of a movement which has its roots in 1970s New York and has since inspired urban dwellers across the world to defy authorities and adopt and cherish neglected public spaces.

GG 3516 Greg, in Zurich, Switzerland, tells of Saturday-night sorties to beautify a traffic island in the city, while GG 158 Luc, in Montreal, documents a "pavement garden" he has been cultivating for four years.

GG 013 Julia, one of the movement’s leading lights, posts pictures and descriptions of significant victories in Berlin, where the Rosa Rose garden in the east of the city has grown out of a vacant lot once covered in rubble and rubbish.

GG 1168 David, and GG Michael 1169, graphic designers in Tokyo, say their motivation was a passion for growing food.

According to Reynolds’ book, the pair began in 2005 by "chucking pumpkin seeds into a vacant lot near David’s home" in the city, and, encouraged by the pumpkins’ progress, continued with a small guerrilla farm on waste ground in the Kamiyacho district.

"It’s about living in an edible jungle," David, who now grows broccoli and radishes land owned by Tokyo city authorities, says in the book.

"Vegetables are best fresh, so I thought they should be grown locally."

Guerrilla Gardening is a crime in Britain — digging land you do not own is classed as committing criminal damage — but Reynolds insists it is a victimless one and is clearly unfazed by encounters with police.

"Yes, by law this is criminal damage . . . but common sense would suggest it is quite the opposite," he said.

"This a win-win war," Reynolds writes in his book.

"Take a public place of wasted opportunity and turn it into a garden. In time victory should be clear to everyone, and probably fragrant too."