Starting an Edible Forest Garden
Are you feeling adventurous? Curious? Want to enhance your relationship with the natural world more fully than simply growing some tomatoes and green beans in the back yard? Most especially, are you thinking of planting an orchard? If so, consider starting a forest garden.
Imitating the Productive Natural Forest
Fundamental to the success of any agricultural (food-producing) enterprise is imitation of natural systems. Enhanced soil fertility, for example, is best achieved by imitating the way natural soil ecologies tend to increase fertility spontaneously over time. Limiting insect damage starts not with the latest magic bullet techno-wizardry from Monsanto, Cargill, et al., but with an attempt to increase insect diversity as much as possible, and grow our crops in the midst of the balancing act that ensues.
In the same way, we should look to the capacity of a natural forest, with no input from humans, to produce an abundance of harvestable food on its own. Indigenous peoples the world over have harvested important parts of their sustenance from forests, reaping where they did not sow. Is it possible for us to imitate such food producing forests, while enhancing their potential diversity and yield through planning and management?
The typical gardener works with annual crop plants, so perhaps a consideration of the role of annuals will reveal key differences if we attempt to “garden” a forest instead. The role of annual plants is typically to colonize and help heal disturbed places. Theirs is a high-energy, in-a-hurry lifestyle. In a single season, the plant sprouts from seed, grows to maturity, ripens seeds, then gives itself up to death, secure in the knowledge that the seeds it has scattered into the world will ensure the survival of its kind. Because of the speed and fecundity of the annuals’ lifestyle, they are able to quickly cover a raw place on the earth (Nature hates bare ground) and protect it from loss of fertility or erosion. This energy intensive lifestyle is only possible in full sun—most annuals will not receive sufficient power for their high-energy task if shaded much from the full force of the sun.
Over time, however, as the annuals protect and build the soil of the disturbed area, they give way to several groups of plants with a different way of doing things. The largest of these, the trees, like the annuals, need the full light of the sun to thrive and support their massive growth. They grow high and wide, forming a canopy of solar collectors (leaves) to harvest the energy of sunlight. Their little brothers and sisters, the shrubs, meanwhile, have learned how to thrive with much less light, in the shade of the canopy, and still ripen edible yield as a part of their reproductive imperative (fruits, nuts, and berries). (Intermediate between these two classes of plants are the vines, growing in the shade but reaching for the full light of the canopy.)
Finally, at ground level are plants that cover the forest floor. They take over from the annuals the duty of preserving and boosting soil fertility, but are a good deal more conservative in their lifestyle. Thus their rate of growth—given the extensive shade—is not as fast as the annuals’; they store food energy in plant parts such as roots to avoid having to start anew from seed in the spring; and they may shift more toward vegetative rather than sexual reproduction. (Seeds are “expensive” in terms of available resource.)
There are of course natural forests that do not fit the pattern, but many—at least at some points in their natural sucession—are perennial polycultures in three layers: canopy, shrub, and herbaceous (ground). Some members of the community produce edible food for animals in the form of nuts and fruits, while the herbaceous plants often have edible stems, leaves, or shoots. With judicious selection, we can assemble a compatible, mutually supportive community of food-bearing plants in all three layers. That is the forest garden.
Note, however, that not all the plants we might choose to plant in our forest garden are intended to produce food for us. Some might be chosen to feed the forest garden itself—that is, to conserve or enhance soil fertility. There are two main types of fertility-boosting plants. Dynamic accumulators have roots that grow into the deep subsoil, “mining” it of minerals that otherwise would never be tapped, and making them available to more shallow-rooted plants. (The minerals are released following leaf fall or die-back of foliage in the late fall or early winter, or may even be washed off the living leaves by rain.) The roots of nitrogen fixers associate with rhizobial bacteria, which have mastered the trick of converting atmospheric nitrogen into nodules of nitrate compounds on the roots of their associated hosts (in a partnership that benefits both the bacteria and the host plant). When those nodules are shed, they provide a nitrogen boost for other plants in the community as well.
The mineral and nitrogen contribution of plants is not limited to the ground-cover plants: Plants in all three layers of the forest can serve as dynamic accumulators or nitrogen fixers. For example, excellent dynamic accumulators in the canopy layer include black locust, black walnut, and shagbark hickory; in the shrub layer, flowering dogwood; and at ground level, German chamomile, Rumex spp. (sorrels and docks), comfreys, and dandelion. Nitrogen fixers (not all of them leguminous) in the canopy layer include alders and black locust; in the shrub layer, Siberian and Russian pea shrub, bayberry, and acacias; and in the herbaceous layer, vetches and milkvetches, wild indigo, lupines, alfalfa, and perennial clovers. Nitrogen-fixing vines include wisteria and groundnut (Apios americana, which produces excellent edible tubers).
Another benefit of a diverse perennial polyculture, in addition to the capture and retention of fertility, is that many of its members provide food and shelter to multiple insect species, amphibians, birds, etc., thus ensuring balances between predator and prey species and preventing excess herbaceous predation of the plants in the polyculture.
Gardeners are used to a fair amount of disturbance and change in their gardens—tillage, digging root crops such as potatoes, crop rotations, etc. In contrast, a natural forest tends to maintain its character over time, and to resist rapid change. (There is of course a natural pattern of succession to a mature state, but such changes take place slowly.) The goal of the forest gardener is to establish a perennial polyculture from which food is harvested with minimal disturbance.