As the shrub or plants get bigger they can be cut down or pruned and the prunings mulched back on the soil to help build up organic matter. At the same time some of the roots will die back and add more nutrients to the soil. This process helps keep the level of fertility very high. Another means of keeping the fertility high is by using deep rooted plants such as daikon, or horseradish, which bring up nutrients from the subsoil to the surface. Another example is the compositae family, such as the daisy.
Many herbs also have useful purposes in the garden or orchard.
The forest garden concept originated with Robert Hart, who wrote Forest Gardening in 1991. Both models, forest gardening and forest farming, preceded permaculture and permaculture has evolved from them. The concept of forest gardening is to design a system that uses a diversity of plants to produce food, fuel, fibres, timber, medicines and other products in a sustainable way. Such a system is resilient in the face of climate irregularities, pests and diseases, utilizes growing space to a maximum, benefits the environment by reducing atmospheric carbon dioxide, and provides other less tangible, moral and spiritual benefits. Like the forest, the garden can integrate some clearings with many edges where there is enough light for growing most vegetable crops.