Overstory #242 - What is a forest garden?

Every forest garden is different because they are designed around the needs and requirements of their users. (Illustration: C. Sobel)

Introduction

A forest garden is a garden modelled on the structure of young natural woodland, utilising plants of direct and indirect benefit to people - often edible plants. It may contain large trees, small trees, shrubs, herbaceous perennials, herbs, annuals, root crops and climbers, all planted in such a way as to maximise positive interactions and minimise negative interactions, with fertility maintained largely or wholly by the plants themselves.

The plants in a forest garden are mainly perennial, which gives the system its long-term nature. Many of the plants used are multipurpose; they may have a main function or crop but will very often also have a number of other uses. Plants are also mixed to a large degree, so there are few large blocks or areas of a single species, and each species is grown close to many others in ways that are mutually beneficial.

A forest garden is in fact a carefully designed and maintained ecosystem of useful plants (and perhaps animals too). The self-fertilising nature comes from the use of nitrogen-fixing plants and other plants that are particularly good at raising nutrients from the subsoil, and from the very efficient nutrient cycling that develops in a forest-like system. The soil is maintained in peak condition by being covered by plants at most times, and garden health is boosted by the use of plants that attract predators of likely pests, and plants that reduce disease problems. Diversity is important too: high diversity almost always increases ecosystem health.

The term 'forest garden' may imply something large and extensive, which is not necessarily the case - forest gardens can be cultivated on any scale, from a small back garden to a field, or several fields. 'Woodland garden' can sometimes be the same thing. Unfortunately, in our culture, 'forest' or 'woodland ' implies a denser, darker collection of trees, which is not the case in a forest garden.

Although the history of forest gardens in the UK and North America is short - forest gardening in the UK has developed only in the last 25 years - there is a much longer history of two-storey systems of food production: for example, plum orchards with rows of soft fruit between; hazelnut orchards with alleys of vegetables between; and undergrazed orchards using large fruit trees.

In many parts of the world, forest gardens are called home gardens, for they adjoin or surround people's homes. Scientists call these gardens 'multistrata systems'. There are thousands of square miles of such gardens, particularly in tropical Asia and Africa, Central America and temperate and subtropical China.

In Chinese forest gardens, high timber trees such as poplar and elm are usually integrated with other crops - something that is less likely to be seen in the UK and North America, where the growing of timber has been 'professionalised' by foresters. Chickens and ducks are also often included in forest gardens in China, where these gardens have been found to have significant economic, social and ecological benefits.

The benefits of forest gardening

People grow forest gardens for different reasons, and, whereas most intensive annual vegetable plots are pretty similar, every forest garden is different because they are designed around the needs and requirements of their users. The following are some of the reasons why forest gardens are cultivated.

Working with the land instead of against it

In a moist temperate climate, the climax vegetation is woodland or forest - i.e. if you do nothing to a piece of land, it will eventually become a forest; the forces of nature are actively moving the land towards woodland. The further your agricultural or horticultural system is from woodland, the more energy it takes to maintain and the more disturbed and distant the system is from a long-term sustainable biological state. So arable fields or annually cultivated ground take the most energy; pasture less; orchard systems still less. Natural woodland takes no human energy to maintain - it looks after itself. Forest gardens lie between orchard systems and natural woodland, and form some of the lowest-energy-input systems for producing useful products.

Low maintenance and high, efficiency

A forest garden will contain a mixture of trees, shrubs, perennial and annual plants. It can certainly also contain annual vegetables, but mostly the ground tends to be covered with ground-covering herbaceous perennial plants of direct or indirect use. Trees and shrubs need little maintenance apart from occasional pruning.

An important part of forest gardening is to try to keep most of the soil covered with plant growth or plant matter at all times; this keeps the soil in good condition, which in turn benefits all the other plants. In annual plant gardens, a large part of the maintenance is spent on weeding, whereas in a forest garden there is little space or opportunity for weeds to establish, and weeding is minimal. In a forest garden there tends to be masses of plant growth, with few gaps between plants, and sometimes one plant has to be cut back to give others room, whereas in 'traditional' gardening, plants are spaced with bare ground beneath - ideal for weed infestations and guaranteed to increase maintenance time.

The biological efficiency of any agricultural system is defined as the ratio of energy outputs over energy inputs; it is not the same as output or yield. Because forest gardens are low-input systems this makes them highly efficient. In terms of outputs, they range from low to high, depending on the design. Tree-based systems can certainly yield as much as arable fields - just look at an apple orchard.

Wide range of products

Forest gardens are designed around the requirements of their users, and can yield a wide variety of products, including fruits, nuts, seeds, vegetables, salad crops, herbs, spices, firewood, mushrooms grown on logs, poles and canes, tying materials, basketry materials, medicinal herbs, dye plants, soap plants, honey from bees, sap products, etc.

High nutritional value

There is plenty of evidence to show that crops from perennial plants tend to be more nutritious than similar crops from annual plants. The more extensive and perennial nature of the root system of perennial plants must account for much of the benefit, for these plants can exploit the soil space more efficiently than annual plants and thus accumulate higher quantities of minerals.

Resilience to climate extremes

Forest-based systems are the most resilient in the face of weather extremes. The structure and diversity of a forest garden ensures good resilience, for example to the impacts of climate change - some of which will be more extreme weather conditions.

Biologically sustainable

The sustainability of forest gardens comes from their diversity and the complex web of below- and aboveground interactions between species. Forest gardens in the tropics have been in existence for over twelve thousand years. Agricultural scientists rarely study them because of their complexity - it is difficult enough to model two species growing together; to model the 100 or 200 species that most forest gardens contain is quite beyond reductionist science methods.

Aesthetically beautiful

Forest gardens are very beautiful places, irrespective of whether aesthetic objectives were part of the design process. When you are in a forest garden it does not feel like a 'normal' cultivated garden - it feels somehow wilder, more jungle-like in places, less managed, less interfered with. In an age where so many people do not perceive themselves as living close to nature, forest gardens can reconnect them to an abundant nature in a way that visits to nature reserves cannot - for we are all participants in nature and consumers of the food and other materials that nature provides.

Although most plants used in forest gardens have direct or indirect uses for people, they can often be ornamental too; and, of course, plants can be included purely for ornament if desired.

Environmentally beneficial

Forest gardens have lots of environmental benefits. They sequester carbon dioxide in the soil and in the woody biomass of the trees and shrubs. Greenhouse gas emissions are negligible. By keeping the soil covered and the soil structure in good condition, forest gardens are excellent at storing water after heavy rains and preventing flooding and erosion. They can shelter buildings, reducing energy use for heating. They are also excellent for wildlife (some of which may become pests of course!); the complex three-dimensional structure and the diversity of plants (whether native or non-native) provide many niches for insects and small animals. A recent invertebrate study in our own forest garden found a higher diversity of species in the forest garden than in a planted native woodland of the same age - perhaps indicating that diversity of plant species is more important than their origin.

Commercial potential

Most forest gardens in the world have a commercial element to them, even if it is just one or two crops from fruit trees - for example a bumper crop of apples or mangoes. To exploit a forest garden on a more serious commercial scale than that, certain features should be introduced during the design stage (see Chapter 9, page 92) - particularly a limit to the diversity (for example, 300 species would be too complex to manage efficiently) and changes to the positioning of species to make harvesting more efficient.

Original Source

This article was excerpted with permission of the author and publisher from:

Crawford, Martin. 2010. Creating a Forest Garden: Working with nature to grow edible crops. Green Books, Devon, UK.

For further information about this book:

Green Books
Foxhole, Dartingon
Totnes, Devon TQ9 6EB

Chelsea Green Publishing
85 North Main Street, Suite 120
White River Jct., Vermont 05001

About the Author

Martin Crawford has spent over 20 years in organic agriculture and horticulture, and is director of the Agroforestry Research Trust, a non-profit charity that researches temperate forestry and all aspects of plant cropping and uses, with a focus on tree, shrub and perennial crops. The Trust produces several publications and quarterly journal, and sells plants and seeds.

Related Editions of The Overstory

• The Overstory #239: The Benefits of Tropical Homegardens
• The Overstory #229: Urban Tree benefits
• The Overstory #222: Forests and human health in the tropics
• The Overstory #216--Introduction to temperate edible forest gardens
• The Overstory #213--Urban Forestry for Multifunctional Urban Land Use
• The Overstory #186--Introduction to tropical homegardens
• The Overstory #147--Major Themes of Tropical Homegardens
• The Overstory #142--Urban Trees and Forests The Overstory #109--Cultural Landscapes
• The Overstory #99--Grey Water for Trees and Landscape
• The Overstory #87--Urban Forestry