Food Forest

A food forest is a planting of trees, shrubs and smaller plants grown together in layers instead of separate blocks. Tall trees form a canopy overhead, fruiting shrubs sit beneath, and herbs, ground covers and climbers fill the space between - as many as eight layers in all. Plants of different heights do not draw on the same light in the same way, so one piece of ground carries several crops at once, and its flowering layers feed pollinators and other useful insects. It starts slowly: the shrub and herb layers give a first real harvest around four years in, and nut-bearing canopy trees take five to ten.

What decides whether it keeps working is light. A closed canopy intercepts most of the sunlight falling on it, and the layers underneath then stop producing while still looking healthy - the commonest way a food forest fails. The aim is a canopy covering only part of the ground, around 5 to 40 percent, kept open by thinning and pruning every year rather than set once at planting. What is cut is left where it falls to rot down and feed the soil; taking it away as firewood takes that fertility with it.

The first three years decide the rest. In dry weather each young plant wants roughly 8 to 19 litres (2 to 5 gallons) every two to three weeks, which across a whole planting outruns hand-watering, so it is usually sited where water already arrives. Browsing animals kill more young stock than drought, so guards, stakes or fencing belong in the plan, and because losses concentrate early, raising replacement plants on site costs less than buying them. The choice that cannot be undone is species: a perennial planting cannot be rotated the way an annual bed can. Black walnut, a common canopy tree, releases a compound that suppresses tomatoes, peppers, potatoes and some trees within 15 to 18 m (50 to 60 ft) of it, and decaying roots keep releasing it for years afterwards.