Forest gardening was made popular by the practice of the late Robert Hart in his book Forest Gardening. Hart worked out a system of forest edge productivity in a temperate climate, but he later recognised that peasant societies had been creating these plant combinations for thousands of years. These people - would have used them for producing food in home gardens (close to home) and representing a high degree of self-reliance. Even today, they can be found surrounding the simpler communities in Mexico, Central America, Benin in West Africa, Sri Lanka and Java.
We should really credit Mother Nature with the design. Pre-historic people, when not chasing animals for food, fed by grazing on fruit, nuts and berries in what they recognised as an edible landscape. For all we know, they may also have eaten nettle tops, willow herb shoots, and various weeds growing in streams. Above all, they were opportunistic foragers who had no intention of tilling soil or tending crops. They ate food from trees, shrubs and vines, and they picked-over the leaves of perennial plants or freely seeding annuals.
Design of forest gardens makes use of the advantages that the natural world provides. Nitrogen fixation through the symbiotic association between soil micro-organisms and plants is an obvious example. Most perennial nitrogen fixing plants (including the shrubs and trees) deliver nitrogen into the soil over and above the nitrogen they use themselves. In addition, fall of their leaves in autumn provides mulch to feed the soil with more nitrogen. Another symbiotic association - that between fungi and plant in mycorrhiza - is only available in perennials, but it is likely that these will form the majority of our plant choices anyway. While the absolute benefit of this second partnership is not fully known, it does aid the plant in resourcing soil minerals such as phosphorus and probably also in water uptake. We can also use plants that are dynamic accumulators of soil minerals. Comfrey is the classic example with its deep penetrating roots bringing up minerals from the subsoil, and making them available at the soil surface when their leaves fall as mulch. Yarrow, tansy and chicory are others.
Above ground there are a plant qualities that we can also exploit. Flowers and berries attract insects and birds, and these are our natural allies in pest predation. Annual companion plants are often used amongst vegetable growing to create a natural balance in pests and predators, but if perennial plants are used instead for pest predator attraction, the range of suitable plants that can be used is increased, and the benefits of permanent plantings can be exploited.
Permaculture Design encourages us look more at the purpose and arrangement of our systems so that they work for us in as sustainable way as possible. Least effort for maximum effect is a design principle in Permaculture, and it argues for using a perennial plant over an annual plant because of less work, but also because it allows a permanent plant community to develop with all the benefits that can bring. The forest garden at Manor heath and the embryonic forest gardens at Springfield re-create the feeding-by-grazing. They are an imitation of a natural forest, designed to achieve economy of space and labour.
A forest of multiple layers
Like a forest edge, the garden is arranged in storeys, tiers or layers, the taller trees forming the canopy, and the shrubs and clumps of perennials forming the lower storeys. Where space is limited, the shrub layer is planted closely to produce edges to the taller trees, and these edges face roughly south so that best use is made of the sun. Traditional tree and shrub foods are grown such as apples, pears, stone fruit and nuts, but there have also been planted less common native food trees such as rowan (Sorbus spp) and edible hawthorns (Crataegus spp) and the ornamentals brought in from N. America such as Oregon grape (Mahonia spp) and Service berry (Amelanchier spp.) all of which provide edible berries (probably best to cook them). A Siberian pea tree (Caragana spp) provides flowers to eat, while a roses give hips for teas and fruit drinks. Culinary herbs are planted as an understorey or groundcover, along with as many uncommon or wildflower salads, roots, shoot or leaf-providing plants as space permits (the tables show examples of plants in each layer).
Most people start off in forest gardening by choosing plants that only have food potential - the purely decorative or utilitarian does not find space. With more experience, particularly in the ways of creating a natural balance between pests and predators, we recognise that this rule is too restrictive. Some plants will earn their place because they are dynamic accumulators or nitrogen fixers, thus aiding in nutrient cycling in the soil, as do the trees as their leaves drop (such as comfrey, tansy, small-leaved lime and alder). It is an aspiration that each plant be perennial so that the amount of annual labour would be minimal. Space can be found, though, for free-seeding annuals (corn salad and landcress) that perennialise themselves by seeding each year. Similarly for tubers such as potatoes and jerusalem artichokes, where some can be left in the ground to grow the next year.
Forest gardening challenges us to learn more about the value and properties of plants and their culture for food. These gardens may make only a partial contribution to our food needs (there are few perennial vegetables in this country) but their productivity for so little work earns them a place in our overall landscape.
The plan shows a forest garden built in 1993 as a public demonstration garden in Halifax. The picture above shows the garden five years after building. The garden is 25' deep and 24' along its shortest width. The plantings are tabulated to the right. A hawthorn hedge is planted along the southern fenced border (right-hand side of paln) and paths through the garden are mulched with woodchip.
T (top layer) 1: pear 2: pear 3: plum 4: rowan 5: apple 6: cherry 7: crab apple 8: service berry 9: apple 10: apple 11: siberian pea tree
S (shrub layer) 1: hazel 2: hazel 3: blueberries 4: bamboo 5: sloe 6: gooseberry 7: hazel 8: barberry 9: rose 10: blackcurrant 11: worcesterberry 12: sea buckthorn 13: blackcurrant
C (cordons) 1: whitecurrant 2: redcurrant 3: whitecurrant 4: to 9: apples 10: gooseberry
c (climbers) 1: boysenberry 2: loganberry 3: wild bramble
SS (self seeders) 1: landcress 2: corn salad and nasturtiums
MB mulch basket with raspberries growing around it
Rh rhubarb, A alfalfa SB strawberries
Mark Fisher - Permaculture Design course handout notes