A food forest is a perennial food garden that incorporates several different permaculture principles.
Perennial food sources are planted alongside other plants that serve various purposes like providing food, attracting beneficial insects, providing wildlife habitat, serving as medicine, etc. The earth is shaped in such a way as to harvest and preserve rainwater. The forest is planted in a way that respects the natural pattern of having several different layers at various heights.
A food forest can produce an amazing amount of food with minimal care compared to a traditional vegetable garden or orchard. If you're interested in this subject, one excellent resource is Toby Hemenway's online training.
The uppermost layer of a food forest is the canopy. It is composed of the tops of various fruit- and nut-producing trees. Unlike a traditional orchard, the canopy is not the only layer in a well-planned food forest.
Below the canopy is the understory. This layer is composed shrubs that thrive underneath the canopy of trees overhead. Understory trees can produce food in the form of fruits, nuts, and berries. Or they can serve some other purpose such as wildlife habitat or pollinator attraction.
Finally there is an herbaceous layer of low-growing plants which cover the ground. The herbaceous layer is often composed of reseeding annual herbs and vegetables, but it can include pretty much any useful plant you'd like to grow. Keep in mind that your plant selection will be somewhat limited by the amount of sunlight that penetrates the canopy and understory overhead.
By interplanting a wide diversity of species in a small area, food forests create a thriving ecosystem with a rich diversity of life above and below the ground. Each species brings its own unique community of soil organisms, insects, and wildlife - and the result is a thriving ecosystem which is resistant to the spread of pests and disease.
Because of the rich diversity of life, there is a greatly reduced need for pesticides, herbicides, fertilizers, or any other supplemental synthetic chemical treatments.
Food forests generate a massive amount of food. With appropriate species selection they can be sustainably grown in any climate from the tropics to the desert. The use of nitrogen-fixing plants serves to preserve the balance of nutrients in the soil. The use of prolific herbaceous plants serves to provide a constant flow of green manure for mulching - protecting the soil from harsh sunlight and preserving moisture below the ground.
Some common choices for the canopy are fruit and nut trees. Species must be selected in accordance with the regional climate, and your nearest permaculture institution likely maintains a list of fruit and nut trees that are likely to thrive in your area.
For the understory, a wide variety of plants can be used. Some popular choices are shrubs that produce berries for consumption by humans or the local wildlife. Other shrubs can be chosen for medicinal uses, for fixing nitrogen, and for their abiltiy to attract pollinators and other beneficial insects.
Food forests are an ideal location to practice the permaculture principle of stacking functions. Many plants are available that serve multiple functions, and these plants can help you to maximize the output and usefulness of your food forest. A few examples follow:
The plants we’ve chosen will collect and cycle Earth’s minerals, water, and air; shade the soil and renew it with leafy mulch; and yield fruits and greens for people and wildlife.
– Toby Hemenway, Gaia’s Garden
Mesquite trees provide a source of pleasant dappled shade to all plants that grow underneath them. They fix nitrogen in the soil and their small leaves thoroughly mulch the soil below during the cold season. Pollinators love mesquite flowers. Their beans are a popular food source with local wildlife, and they can be harvested by humans to make flour for cooking and baking or for fermentation. Their wood is famous a cooking fuel and is also useful as a material for tools and structures. One plant, many functions - this is stacking functions.
Roses are a good example for the understory. Their flowers provide food for bees and other pollinators. They blanket the ground below with rose petals. Their hips can be used to make nutritious and medicinal teas and jellies for human consumption.
In the herbaceous layer, consider comfrey and mullein. Both of these plants provide services to the soil, pollinators, wildlife, and people. These are only a few examples of plants that can help you to stack functions in a food forest. The world is full of plants like these, and learning about them is one of the most rewarding aspects of practicing permaculture.