Permaculture plant guilds combine three or more plants to mirror an ecosystem — producing food, building soil health, and providing food for pollinators. To learn more permaculture principles, check out out Tierra: Online course.
Permaculture Principles for Practical Gardeners and Farmers -
Finally, a permaculture article that doesn't read like a religion. These 9 permaculture principles are based on the concept of mimicking Nature. Suggestions and examples are given, so you can implement them in your own garden or farm. Just the science; no politics.