"Permaculture is a movement that is coming into its own, and the concept of creating plant guilds in permaculture is at the forefront of every farmer's and gardener's practice. One of the essential practices of permaculture is to develop perennial agricultural systems that thrive over several decades without expensive and harmful inputs: perennial plant guilds, food forests, agroforestry, and mixed animal and woody species polycultures" -- from publisher's web site.