The EFG at JMU has a diverse assemblage of fruit trees and shrubs planted in a Trios design. The Trios design is modeled after Stefan Sobkowiak’s 5-acre permaculture orchard in Quebec, Canada. Originally called NAP after the intentional interspersing of Nitrogen fixers with Apples and Plums/Pears, it can more broadly include other crop trees. The Figure below demonstrates the Trios design, where each example fruit tree is proximal to a nitrogen fixer. One characteristic of this pattern is that no fruit tree is next to its own species in the row or in between the rows. If a tree gets infested with a pest(s), the Trios design reduces the likelihood that the pest will infest another tree of its kind. Rather, individual trees act as “islands” to isolate the deleterious insects. This design therefore reduces (or eliminates) the use of fertilizations and pest/disease control products.
Although 1/3 of the forest garden trees do not produce edible fruits, intermixing leguminous trees among fruit trees performs another essential service: it improves fertility. Under the Trios design, a circular, closed-loop system akin to natural forest ecosystems may be feasible. In Stefan Sobkowiak’s 5-acre permaculture orchard, for example, no fertilizers have been applied since 2007 and the fruit trees yield as much as conventionally grown fruit trees. The N-fixers in Stefan’s orchard are predominantly honey locusts. While honey locusts do not form root nodules, they are thought to release a large amount of nitrogen via pruning and subsequent root sloughing. The strong and straight trunk structure provides ideal trellising for vines, kiwi, and grapes. In the EFG, a thornless variety of honey locust (Gleditsia triacanthos) serves as the primary nitrogen-fixer. Honey locusts are ideal as their canopy is not as dense as other hardwoods (less shading), their wood is straight and narrow (good for trellising), they attract beneficial insects, and the leaflets and limbs provide great mulch (chop and drop).
