Martin Crawford of the UK’s Agroforestry Research Trust is one of the world’s best recognised practitioners of the art of "forest gardens".
[youtube=http://www.youtube.com/watch?v=GFbcn06h8w4]
Martin’s forest garden has an enormous diversity of plants. Most, but not all, are edible. Those that are not edible would be regarded as a waste of space to most farmers or gardeners, but these also serve valuable purposes and earn their keep in the garden — ultimately also being responsible for not only increased resiliency, and thus less labour input, but also increased productivity. Some attract beneficial insects, or insect-eating birds. Some may distract/confuse the more troublesome insects by their colour and scent. Some may provide sustenance and habitat for pollinators. Some are bio-accumulators (i.e., for example, they might bring minerals up into the soil profile layers where they can later be accessed by other food-producing plants), or some might provide protection from wind and extreme temperatures to their more fragile peers.