In a sense, the legendary Johnny Appleseed was a guerrilla gardener, planting apple trees as he traveled across Ohio, Indiana and Illinois in the late 1700s and early 1800s.

The term, though, is believed to have originated in 1973 when a group of people in New York City planted a vegetable garden in a derelict private lot.

In some countries, the practice is related to land rights and reform.

Some guerrilla gardeners carry out their actions at night, in relative secrecy, while others work more openly, seeking to engage their community.

In 2004, Richard Reynolds started a blog at www.guerrillagardening.org about his "illicit cultivation around London."

He says that while it technically is illegal, "you're also unlikely to go to jail for improving neglected crevices and crannies."

Reynolds also provides a 12-step guide for people who'd like to join in.

His first tip is to find "orphaned land - grubby patches of unloved public space" and to appoint yourself as its parent. Ongoing tending and watering become your responsibilities.

You also should select plants that are hardy, able to stand up to drought and cold and the sort that will make an impact through their beautiful color or productivity.