Establishing a Forest Garden

The following article was kindly contributed by Kip of Victoria Farm. Kip is currently establishing a Certified Stockfree-Organic forest garden in Geneva, Florida, and has recently taken a forest gardening course given by Martin Crawford, director of the Agroforestry Research Trust at the Schumacher Forest Garden site in South Devon, England.

Establishing a Forest Garden

Forest gardening involves participation in an ecosystem as opposed to trying to impose and sustain an unnatural and unstable monoculture over the successional forces of nature. They can be created by selecting all the plants to build an ecosystem, or by adding plants to an existing ecosystem. Smaller forest gardens can be planted all at once for an ‘instant’ ecosystem but larger gardens are usually planted one step at a time.

As Martin Crawford wrote in the Agroforestry News, there are 4 different stages leading to a mature system. The first (optional) stage is for windy sites and involves putting in a windbreak hedge system.

If wind is not a factor, or after suitable protection is achieved, the next stage is the planting of the canopy and other sun-loving shrubs, including nitrogen fixers. When proper plant spacing has been used, there will be lots of sunny space between trees and shrubs for several years. Plants that need partial shade may have a difficult time during this time. These areas could be used for annual vegetable cropping or for short-lived perennials until shade begins to prevail. Clearings could be designed in for sun loving species, or edges could be utilized for the same purpose.

When the canopy and shrub layers begin to provide increasing shade, the shade-tolerant understory can be planted.

Finally, after a few more years the forest garden will near the mature stage. Deep shade-tolerant species can be added, as can climbers, which at this point will not threaten to overwhelm their hosts.

Acquire or select a site

Whether planting all at once, adding to an existing ecosystem or working in stages, the process cannot begin without a site. In many cases, land choice options are limited. The question ’what would be the ideal site?’ often becomes ’could this work here?’ Forest gardens can range in size from a thousand square feet or even less to as large as a few acres. Robert Hart’s very productive garden in Shropshire, England, measured 85 by 45 feet. In the classic permaculture book Tree Crops: A Permanent Agriculture, author Russell Smith describes establishing tree systems successfully in areas considered unsuitable for conventional agriculture. Hilly land, irregular pieces of unused property, urban lots, rooftops, residential back yards and many others; forest gardens have been planted in more places than one might imagine.

Once a site has been located, some assessment and research will soon determine its suitability. A person does not always have to own the land, as forest gardening makes a great community or school project (given permission from the landholder). Something to consider is that forest gardening is a long term project; it does require some commitment.

Assessment

Because a forest garden will mimic a complex ecosystem involving synergies in both space and time, it is best to be equipped with as much accurate information beforehand as possible.

Become intimately familiar with the land of interest. Have soil testing done, find where the frost pockets are, approximate the earliest and latest frost dates, check into average cooling hours if in southern areas, get a feel for the direction and velocity of the strongest winds, determine the length and severity of dry and wet periods throughout the year, take a look at the types of plants already growing on site and nearby, consider protection from foraging herbivores and gather any other relevant information that is available.

Planning and research

Planning and research can be done concurrent with the initial site assessment. The internet is a powerful research tool and can deliver information directly or lead towards people who have valuable knowledge and experience in the desired area of interest.

It is relatively easy to draw up a wish list of useful crops and it is not difficult to determine which are likely to be most successful. Seek out the most vigorous varieties with the best disease resistance for your area. Consider selecting groups of crops that fruit over the longest time frame possible for your climate.

Canopy tree spacing may be a little wider than that found in orchard crops to allow more light to understory plants. Pay attention to the light requirements or shade tolerance of each plant and consider where and when to establish it.

Pollination needs are important, as is separating species for pest deterrence. Pollinators placed within 50 feet of each other but not next to each other are an example. Try to find out something about the root structure of plants that will be close together; for example, a shallow rooted species like a mulberry tree surrounded by tap rooted species such as comfrey might be better than two shallow rooted mulberries adjacent to each other due to reduced root competition.

Next make sure ecosystem needs are met. Intensely planted heavily fruiting forest gardens will probably need more nitrogen and potassium than usually is available through the nutrient cycle. These needs can be addressed with fertility plants.

Take a look at the multitude of different nitrogen fixing trees, shrubs and ground covers available, paying attention to their needs and the additional goods and services that they have to offer. Give extra criteria points for multi-function plants, such as a nitrogen fixer that is also a mineral accumulator, and/or offers insect habitat or edible fruit, etc. Living plant sources of potassium are few in comparison. Comfrey is a good one for most temperate areas, and is also one of the best mineral accumulators. Consider a few other nutrient accumulating trees, shrubs or plants, again along with their needs and benefits. Plan how you might concentrate a variety of fertility plants around heavy feeders.

Give some thought to providing habitat, pollen and nectar to beneficial insects. Try to arrange for many different shapes, sizes and colors of flowers to be in bloom continuously throughout the growing season, or all year long in warmer climates.

Aromatic plants such as lemon balm, mints and others have been said to confuse pests. Many useful culinary and medicinal herbs can be scattered around for this additional purpose.

It is also worth noting which plants have running or suckering characteristics as they may require rhizome barriers or other management techniques.

Do all of this before reaching for the shovel!

How can so much information be condensed into a workable plan? Site, soil, zone, microclimate and other conditions will help narrow the candidate plant list considerably. Light, moisture, space, fertility, pollination and other plant needs will crop it down some more. Aesthetics can and should be applied, as should practicalities of access, proximity to house, water, compost area and other concerns. If the list is still too long, then it is time to pick favorites!

Some may wish to plan to every last detail and others might focus on a more general canopy, windbreak and fertility emphasis, leaving much of the understory to be designed years later. Drawing a scale map and cutting some circles the size of mature trees will allow you to visualize many different scenarios.

Windbreak

If needed, design and plant a dense hedge system. Tree crowns should touch, even interlace, and shrubs should grow up into the lower branches of the trees for a good buffer. Wind protection will be provided for up to a horizontal distance of 8 times the height of the windbreak. Consider shade areas created by southern breaks. There are many wind resistant species that are also nitrogen fixing, mineral mining or are edible (however, yields of edibles will be lower due to root competition). Insect or wildlife habitat would be additional secondary functions. Thorned varieties in dense plantings make nice living fences as well.

Site prep and fertility

Some may choose or need to prepare the site before any planting. Building the soil through legume and/or mineral accumulating cover crops during the assessment year might be appealing. Compacted soils may need to be dealt with, smother mulches may be needed for ’instant’ applications.

Canopy establishment

Trees in the canopy level should be planted such that crowns do not touch at maturity. If the crowns were allowed to close in, the ecosystem would lose some productivity from loss of available light to the understory. Some thought should be given to shade areas produced by different heights and densities of canopy trees and how the understory will be affected. For smaller sites, dwarf variety trees or large shrubs might be chosen for the canopy to allow more diversity for given space. Once establishment has begun, assessment and replanning will be ongoing to some extent.

Shrub level

Many shrubs can be planted with the canopy or shortly thereafter. It is good to establish nitrogen fixers as soon as possible. Give the same planning considerations to the shrub layer as the canopy received. Care should be taken to allow access to fruiting canopy trees for ease of harvest. Continue to think a step ahead and visualize future shade conditions for the herb and ground cover level, particularly if sun lovers are desired down low.

Herb, root and ground cover understory

When the canopy and shrub layers have created partial shade conditions on the ground, it is a favorable time to put in the final layer of the forest garden. Often this involves surface preparation using light excluding or other smother-type mulches. These can be made of cardboard, old carpet, agricultural fabric or similar left in place for up to a year to sufficiently suppress grasses or other undesired plants without damaging the roots of existing trees and shrubs. When the ground cover dies, the soil food web will be fed instead of being damaged as it can be from tilling.

Plant spacing at this level is complicated slightly by the clumping, running or other habits of the species of interest. As in previous stages of establishment, this should be well thought out and there is much written in forest garden literature to draw from. Another good rule of thumb from Martin Crawford on this is to try to keep different species of plants limited to 2 or 3 per area or ’patch’. The forest gardener is always looking for mutually beneficial combinations, but ecosystems are quite complex already. It is easier to build synergistic associations with fewer variables in the equation.

This is also the stage with the highest number of individual plants required. For larger sites, a polytunnel or greenhouse is very useful for propagation and can sometimes pay for itself from money saved at the nursery.

Fungi

Fungi cultivation requires no light and is ideal for the shadiest areas of the forest garden. Many good books and commercial spore sources are available and should be consulted. Fungi crops, like forest gardens, can be quite productive. A single hardwood log inoculated with shiitake spore can produce mushrooms for years. There are also many edible secondary decomposing fungi that feed on wood chips or sawdust. Due to the existence of many look-alike poisonous fungi, exact identification and/or commercial spore sourcing is a must.

Maintenance stage

A well designed forest garden will require very little maintenance. The main tasks will include removing any unwanted ‘tree weeds’ that might try to take the garden towards a climax forest condition if allowed to remain, trimming back climbers or other plants overtaking their neighbors, maintaining access paths, harvest and food preservation. Prunings can be left on the forest floor to decompose and feed the soil. Fruit that is not eaten can also be allowed to fall back to the earth to reenter the nutrient cycle. The forest garden should take good care of itself, and of those who participate in it.


7 May 2011
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