In one of our recent articles I wrote about companion planting and the specific plants my husband and I have grown successfully together -or not- when growing our seasonal food crops.  This time I’d like to write about the function and use of plants grown in polyculture and how each plant species has inherent characteristics that benefit an entire plant community or plant guild (polyculture is growing many different types of plants together -as compared to monoculture).

SYNERGY

Similar to companion planting when you design a plant guild or forest garden you are grouping together plants which relate synergistically –benefiting each other by warding off pests or by supporting each other in some specific way.  YET within a plant guild or forest garden we are trying to do more than compliment the plants individual relationships we are trying to compliment the arrangement as a whole ecosystem –soil biota to unique microclimate, insects to animals, plants to people.  Creating plant specific polycultures which provide food for humans as a priority and either preserve or create an ecosystem is a step beyond companion planting and toward a more diverse and secure future -for food and natural resources.

A forest garden can be many things… in our trials and experimentation it is comprised of several plant guilds grown in a spatial pattern that becomes self sustaining over time.  A plant guild is simply a polyculture of plants -generally with a central plant species- when grown together make efficient use of space and resources requiring little input from humans.

GOALS

The ultimate goal for a forest garden should be clear from the onset of design. For example: when we designed our forest garden we wanted to grow fruit and nut trees, lots of different types of berries, edible flowers and fresh greens all year.  We also wanted the forest garden to achieve a balance in pest populations, be able to withstand drought, control pervasive weeds as well as build soil health.  Once the goals are set the spatial pattern of the garden can be determined.

PATTERNS

Identifying patterns found in nature, such as a spiral on snails and the curves in a natural swale or river allow us to mimic them within our gardens.  Pathways which bend and curve are not only more eye pleasing than straight lines but are also more efficient in their use of space. Creating nooks for trees and other plants along side a meandering path are perfect areas for placing plant guilds. Easily accessible pathways combined with several nooks of diverse plant guilds becomes your forest garden.

RESOURCE EFFICIENT

In consideration of water resources you can take this meandering pathway utilizing nooks concept one step further: if you build slightly elevated pathways some nooks along the way could be turned into depressions within the terrain and serve as mulch basins for a rainwater harvesting system.  Mulch basins (some planted with water tolerant species) would conserve water in the soil for nearby plants to utilize all year reducing the need for irrigation over time.  Designing a forest garden infrastructure like this when patterning, especially in an arid climate, is truly an effective use of water and other resources. One can begin to see just how forest gardening goes beyond companion planting by incorporating resource efficiency into the landscape.

STRUCTURE

Before going into the function and use of plants within a forest garden let me define the basic architecture or vertical structure of a forest garden –as conceptualized by Robert Hart and many other originators of this perennial gardening idea.

A forest garden has a vertical structure comprised of several layers of plants; ideally each layer provides a benefit to its neighboring layers (see my simple drawing for visual aid):

   1. Canopy plants (which can be fruit or nut trees, tall nurse or pioneer species or simply currents or berry shrubs)

   2. Subcanopy plants (lower plants utilizing some shade of the canopy plants)

   3. Shrub plants (wide often habitat forming plants provide shelter and shade in sunny aspects)

   4. Herbaceous plants (often edible and medicinal plants grown on either sun or shade side of trees)

   5. Vining or climbing plants (plants that climb their way up subcanopy and canopy plants)

   6. Groundcover plants (shade the soil conserving moisture and prevent soil loss)

   7. Deeply rooted plants (become nutrient pumps for the surrounding soil enhancing it’s fertility)

PLANT SPECIFICS

Forest garden structural layers (the canopy, subcanopy etc.) made up of diverse plants grown in polyculture all have specific characteristics which function for the forest garden as a whole.  Understanding what particular habits plants have, how plants can be used and how they function inherently is one of the most important considerations when designing a plant guild or forest garden.  

Listed below are plants with inherent characteristics -beneficial uses and functions- to begin to understand when designing plant guilds and forest gardens. Keep in mind this list is not exhaustive!

    * The central plant species (all plants around this plant are chosen to support it’s overall growth and health –usually an edible plant)

    * Edible and medicinal plants (roots, shoots, leaves, fruit, seed etc.)

    * Companion plants (plants that have an overall benefit to one another)

    * Insectary and nectary plants (insects depend on these plants for food, shelter, reproduction etc.)

    * Aromatic Pest Confusers (plants that confuse pest insects with strong odors e.g. onions, garlic)

    * Wildlife plants (birds and other animals rely on food and habitat these plants provide)

    * Nitrogen fixing plants (association between N fixing bacteria and plant roots creates free N)

    * Dynamic accumulator plants (mineral miners collect nutrients = free nutrients)

    * Bulbs and large rooted plants (soil structure diversity, ability to absorb/mine minerals)

    * Coppice, espalier, hedge or thicket plants (diverse ways of growing plants)

    * Ground cover plants (protects the soil, conserve water and create healthy soil level habitat)

    * Fertility and mulch plants (free nutrients and green mulch for seasonal chop and drop practices)

    * Animal forage and fodder plants (reduce outsourcing of food for livestock such as chickens)

MULTIPLE USE

Most plant species will have more than one of the characteristics listed above.  Using our permaculture principles try to remember to stack as many elements and functions as you can.  For example, when choosing a plant guild’s central species one could pick a Pear and use it as a canopy or subcanopy tree.  Pear trees have at least 7 essential uses and functions:

   1. an edible fruit to humans

   2. a companion to chives, carrots, bulbs, borage, strawberries, nasturtiums, comfrey and more -in our experience

   3. provides wildlife shelter for birds as a place to rest or nest in the branches

   4. a nectary plant for honey bees while in bloom

   5. can be grown in diverse ways like espaliered on fences or walls, in thickets or as a standard tree

   6. can be coppiced for wood material

   7. provides some (hopefully not much!) fallen fruit/insects for animals/chickens to feed on

GUILD BUILD

Creating a site specific species matrix chart is the best way to pick out the right plants or ‘guild build’ your forest garden. Edible Forest Gardens Volume Two: Design & Practice has a comprehensive species matrix chart in the appendix for the East Coast but it is limited for my needs on the West Coast so I’ve created several charts over the years for myself and Clients.  These on-going reference charts are easy to follow and describe as much information as one can find about a specific plant, its habits, uses and functions overall. And they are dynamic charts, ever growing and evolving themselves.

I wrote a long time ago about the Pear Tree Guild (pictured above) but always wanted to go into more detail. Take a peek at the charts I created for the same Pear Tree Guild (below).  I’ve divided them up into sections for easier viewing in this article. The first chart references the plants genus, species and common names. Next is the family name –diversity of plant families is important to guild diversity.  Next in this chart is the basic information on the plants light, water and soil tolerances. Note for the Pear Guild they all have just about the same tolerance levels. The light differs because of sun aspect -sun and shade sides of the tree. Those with mixed sun/shade are best suited for the shade side of the tree.

Next in the chart (pictured below) is the form of the plant. Is it a small herb or tall shrub? We note the habit -mat forming as in mints- and the root habit -if known- is also important.  The maximum height and width of the plant is extremely important when considering space. Where it is native to, the preferred habitat and successional stage of the plant are also things we like to note about the plants when guild building.

Following that chart is where it gets really interesting. Is the plant edible or medicinal? Is it a nitrogen fixer or a dynamic accumulator? Does it attract or support wildlife? Can it function as invertebrate shelter –meaning can it shelter insects we find to be beneficial to the plant community and us? And finally is it a nectary plant -a plant that feeds bees and other nectar loving creatures- and if so when does it flower?

Last the chart questions if the plant is a ground cover -a living mulch to retain moisture. What other kinds of functions or uses the plant may have -does it coppice well? Can it spread –and if so is it dispersive or expansive? Dispersive means it spreads by seed and expansive is generally by runners. The mint is expansive as we use it to control Bermuda grass which it successfully out-competes. Also this chart asks if the plant is poisonous to humans or livestock. And finally any other notes of information we have gathered that is not yet listed. Here is where we will discern whether a plant is an aromatic pest confuser or APC, as all Alliums are. APC plants confuse pests with their strong smells.

While it may seem like quite a task to generate charts such as these it is truly fun to do and will help you understand the many different characteristics plants have and how they will benefit you and your gardens now and in the long term.

By and large we have found ‘guild building’ our forest gardens a type of perennial gardening system that is truly beneficial to all involved -as well as low maintenance if following the concepts given above. There are many people involved with forest gardening around the world and it is worth trying out new plants together to see what can be achieved in your garden.  For more information on community forest gardening check out what the city of Seattle is doing…  Happy Guild Building!

References:

Forest Gardening: Cultivating an Edible Landscape Robert A de J. Hart Original publication 1991 Green Books, Ltd. ISBN: 0930031849

Edible Forest Gardens Volume 1 and 2 Ecological Design and Practice for Temperate-Climate Permaculture by David Jacke and Eric Toensmeier 2005 Chelsea Green Publishing Company ISBN: 1-931498-80-6