Guidelines for Perennial Polyculture Design
Polycultures (or “guilds” as we sometimes call them) are an essential element of agroforestry and permaculture design. Here I’ll define them this way:
• Plantings containing at least two plant species;
• Designed to minimize competition between the plants;
• Designed to maximize competition between the plants;
• Designed to optimize management and ease of harvest;
• May also include livestock, cultivated fungi, and other elements.
Polyculture design can be bewildering and even intimidating. I’ve been planting and thinking about polycultures for over two decades. During that time I’ve planted a lot of failed polycultures that didn’t work for one reason or another, as well as some successful ones. I’ve also visited many sites in many climates and seen polycultures functioning very well – especially in the tropics, where agroforestry systems are much farther along than my cold temperate home.
I’ve assembled a set of guidelines for designing polycultures, that I’d like to share with you. They are a work in progress and far from perfect, but, in concert with the design process shown below, they have helped hundreds of people in my courses and workshops to feel ready to go home and design and install their own polycultures.
These guidelines, drawn in part from Edible Forest Gardens as well as from experience, can help us tap successfully into the way nature functions. On several occasions I have been visiting a faraway climate to teach. As I investigate the local species, I begin to play with polyculture design. More than once I’ve then headed out for a hike and seen those same plant combinations growing in the wild.
Polyculture Design Process
Polyculture design is a phase that comes rather late in the permaculture design process that Dave Jacke and I lay out in Edible Forest Gardens. The following steps should already have taken place to some degree:
1. Goal setting
2. Site analysis and assessment
3. Design concept
4. Schematic design (and perhaps some detailed design)
As a result, you should have a particular area (a “patch”) in mind for your polyculture. Characterize your patch as follows:
• Name or title
• Key products or functions that you want it to fill (e.g., fruit production, beneficial insect area, livestock fodder, etc.)
• Review the conditions in the patch (e.g., sun, soil, moisture, slope, etc.)
• Determine the desired “architecture”
o Layers (which are present – will there be tall trees, only shrubs and lower, etc.)
o Habitat type and feel (e.g., orchard vs. wild and woolly; thicket, forest edge, meadow, etc.)
o Size and form of plants (e.g., not taller than 2 meters, etc.)
• Intensity and forms of management (e.g., how intensive; how diverse; how much care; will it be irrigated; will poultry be rotated through; will you use special techniques like coppicing, chop and drop, or fire management, etc.)
• Soil fertility plan (nutrient budget: will you provide compost, urine, etc. I’ll address this more in an upcoming article)
• Infrastructure to be installed (e.g., pathways, irrigation, fencing, etc.)
At this point, you should develop a species palette for this polyculture. From the longer list of species you are considering for the whole site, select those that are a) suited your site conditions and b) meet your goals as far as size, uses, and functions. When I’m teaching this exercise, I prepare a list ahead that looks something like this:
I then add more categories, like: plants 4-15, 2-4, 1-2. 0.5-1, and 0-0.5 meters tall, as well as one for vines. Here’s an example for my cold humid climate of the northeastern USA, with a few columns merged to make it fit more easily here.
Each region already develops its own list of useful species, including the often-overlooked native ones. One might also add or replace columns – for example, in arid regions, moisture is more the variable than light, or your could add many columns for complex sites. For teaching purposes I find a single site variable (light, moisture, etc.) keep things simple and teaches the process. People can always add complexity later once they’ve got the basics down.
When teaching I provide 3-6 sample species in each height category for people to work. In each height category I also try to provide species for sun and shade, some edibles, some nitrogen fixers, and some native and some non-native species. Of course if you are designing for your own use, only include the species you want – though it may help you identify some gaps that need filling, like a nitrogen fixing groundcover for shade, for example. Add columns like chop and drop mulch, firewood species, honey source, or whatever else you like.
These are broken up by theme. They are not the only ones for certain, and there are surely important exceptions to all of them. Nonetheless I quite like them and they have been useful to many of my students over the years.
• Select species that:
o Meet your goals for the patch
o Are tolerant of the conditions there
• Use 2-7 species per polyculture (keep it simple)
• Fill key uses and functions first (start with your most important goals, like fruit production or livestock fodder)
• Select species with similar management needs (like the same level of irrigation or number of visits per week; this is in line with the permaculture zone system)
• Start with the tallest species and work down
Spacing and Patterning Guidelines
• Determine the mature height and weight of each species (how big will they get when they grow up under your planned pruning and/or coppicing regime, if any)
• Set spacing between clumping species (those that will not spread vegetatively)
o Usually such that the edges of their crowns are just touching, or ideally quite a bit wider
o This varies quite a bit with climate – in areas with intense sun (lowland tropics, high deserts) spacing can be much closer. On the other hand spacing should generally be wider in more arid environments.
• Plant runners (aggressively spreading species) that are shorter than adjacent clumpers (to make sure runners will not smother clumpers)
• Plant shade lovers under taller plants
• Keep pollination needs in mind
• Plant the tallest plants to the north in the northern hemisphere, to the south in the southern hemisphere.
Functional Species Patterning
• Plant soil builders like nitrogen fixers and mulch plants in every polyculture or patch where they will be needed (so as not to have to cut and carry the material to another area)
• If all nitrogen is to come from nitrogen-fixing plants, remember they need 25-40% of the overstory or 50-80% of the understory
• Nitrogen fixers and beneficial insect plants don’t need to be in harvest reach of pathways
• Provide complete ground cover
• Evergreen, shade-tolerant groundcovers are excellent
• Running groundcovers help fill in empty spaces
• Try to include some beneficial insect species in each polyculture (though the insects can fly 15-30 meters, so they don’t need to be right next to the crops they are planting, and could be clustered in islands or strips)
• Is there a niche for sun-loving, short-term crops in the early years (annual vegetables, strawberries, papayas, pigeon peas, nitrogen-fixing cover crops, etc.)
• Wait to plant shade lovers until there is enough shade (you’d be surprised how many shade plants I’ve killed through impatience)
• For living trellises, wait to plant climbers until the trellis tree is well established (again, I’ve killed a lot of plants this way even though I know better)
• Consider livestock integration requirements if necessary (see my article on livestock in the food forest for more)
• Choose species of similar vigor (so they don’t smother each other)
• Match species to patch management style
• Choose species with similar irrigation and fertility requirements
• Will any aggressive species require control (e.g., rhizome barrier?)
• Make sure to have access for harvest
• Will there be a need to pick up fruits and nuts from the understory? (If so, stinging or spiny understory species are undesirable; understory could be harvest-season mow or chop compatible; understory could be tarp-compatible)
• Don’t mix toxic species with similar-looking edible, especially in the same layer (we did this with daffodils and garlic chives, oops!)
• Consider adding more shade-loving edibles (mushrooms, shade fruits and vegetables, coffee, cacao, vanilla, etc.)
• Make sure root crop harvest does not damage roots of any sensitive species
• Does the polyculture meet your goals? (products, functions, architecture, management style)
• Are conditions ideal for the “keystone” (most critical) species from your goals?
• Is each species adapted to its niche?
• How will conditions change when the polyculture is mature? What changes will this produce?
• What steps must be taken in preparation for planting?
An Exercise for Classes and Workshops
Here’s the outline I use when teaching these ideas – feel free to use and adapt it as you see fit.
1) View some sample polycultures (could be some slides from the Apios Institute website, or even better tours of real perennial polycultures right there on the teaching site)
a. Discuss what is and isn’t working
2) Review the polyculture design guidelines
a. I usually have the participants go around and each read two guidelines out loud
3) Break participants into groups of 3-6
4) Pass out and review the species palette (the list shown above shown above) created for the region and site
5) Set up the goals and constraints of the exercise
a. They can only use the species from the handout
i. They have the rest of their lives to create polycultures
ii. This keeps them from getting overwhelmed by a long list
b. 2-7 species
c. At least one nitrogen fixer, and one groundcover
d. Don’t tie it to a specific site
i. It’s enough to learn how to plug the pieces together for this exercise, they can connect it to real sites next time (e.g. in final design exercise for class)
e. “Bonus points” for a beneficial insect attracting species
f. Remind them not to stress too much
i. There is no risk of these actually being planted!
g. Remind them to be a polyculture
i. Be nice to each other!
ii. Whatever guidance you usually provide to keep things creative and cooperative and avoid stress and arguments so people can learn
6) Provide each team with its own goal and conditions
a. Could just be simple like: “full sun”
i. Usually I just say groups as follows:
1. Full sun no restrictions
2. Part shade no restrictions
3. Full shade no restrictions
4. Full sun native species only
5. Part shade native species only
6. Full shade native species only
a. This one always finishes first because they have so few options!
b. Or more complex: “nectary planting for part shade”, “living trellis for perennial beans”, “elderberry companions”, “productive thicket” etc.
c. Prepare presentation
i. Who will present? Polyculture name, goal and conditions, species, drawing or map welcome
7) First step: make a revised species list by crossing out species that won’t work (too tall, not shade tolerant, otherwise don’t fit them goals and conditions), or highlighting those that do
8) Start at the highest layer and work down
9) Next step: follow the guidelines on the handout.
10) I circulate and check in every once in a while, make sure they are on right track (usually takes 20-40 minutes to complete a polyculture)
11) Presentations (3-5 minutes per group)
Almost 100% of my students have had success in this exercise, and they tend to feel it makes a somewhat intimidating process much more approachable. Please try it out, I hope it will be of use to you as well!