Sectors in permaculture

What sectors are for

No garden exists on its own. Every day energies cross its boundary that nobody planted: sunlight, wind, rain running off the neighbour's field, cold air sliding down at night, the sound of a road, and in a dry summer perhaps the smoke of a fire. Sectors are the tool for drawing these forces on the plan. Each one gets a wedge that opens from the centre of the site towards the direction from which it arrives.

Bill Mollison set out sectors in Permaculture: A Designers' Manual (1988), and in Introduction to Permaculture (1991) he grouped them with zones and slope under efficient energy planning. The division of labour is clear. Zones order the energy that comes from inside a system, above all human attention and walking. Sectors record what comes from outside and cannot be switched off. Zones say how far away an element may be; sectors say on which side it belongs.

Permaculture teaching often names three possible answers to each sector. An energy can be blocked, as a hedge breaks a cold wind or a screen hides an ugly view. It can be channelled, as a swale leads runoff into the soil. Or it can be welcomed, as when a tree is thinned to let winter sun into the kitchen garden. Which answer fits depends on the season, because the same sun is welcome in January and a burden in July.

How to draw a sector map

1. Start with a plan. Any simple sketch with a north arrow will do, better still a base map with contour lines. Mark the centre: the house, or the part of the site used most.
2. The sun. Note where the sun rises and sets at midsummer and midwinter and how high it stands at noon. At about 40 degrees north, the latitude of eastern Sardinia, the noon sun climbs to roughly 74 degrees above the horizon in late June and reaches only about 27 degrees in late December. A stick in the ground and its shadow, noted on a few dates, already show a lot; sun path charts and apps do the rest. Shade cast by buildings and large trees is drawn in as well.
3. The wind. Distinguish the prevailing wind from the rare storm wind and the hot wind of summer from the cold one of winter. Trees bent or shorn on one side, a strip of cloth on a pole and the experience of neighbours tell more than regional averages.
4. Water. Walk the land during heavy rain. Where does water enter, where does it collect, where does it cut rills? This line connects directly to keyline design and to rainwater harvesting.
5. Fire. Ask where a wildfire would most likely come from: usually the side of hot, dry winds and unbroken dry vegetation, and above all from downhill, because fire runs faster up a slope. Local fire services and older neighbours know the history.
6. Cold air and frost. On calm, clear nights cold air flows downhill like water and pools in hollows and in front of obstacles. Mist and frost at dawn show its paths.
7. Views, noise, neighbours. Mark what is worth seeing and what should be screened: a road, a floodlight, a neighbour's spray drift.

Each force goes onto its own transparent sheet or digital layer, so that it can be corrected when a second year of observation says something different. Andrew Millison of Oregon State University recommends internalising the path of the sun so well that, on arriving at a place and finding the cardinal directions, one knows at once where the sun will rise and set.

An example from the world: Melliodora

David Holmgren, co-originator of permaculture, lives on Melliodora, a property of about one hectare on the edge of Hepburn Springs in Victoria, Australia. Fire there is not a theory. According to Holmgren, the site has had a plan to stay and actively defend against bushfire since 1988, and his earlier work on building against bushfire, published as The Flywire House, also informed the design of Melliodora. In February 2019 Melliodora faced its first direct bushfire threat in thirty years. After the Black Saturday fires of 2009 he wrote a 52-page report on bushfire-resilient landscapes for his community and the Hepburn Shire Council. By his own account, his focus on bushfire intensified after the Ash Wednesday fires of 1983. Melliodora shows what the fire sector means in practice: a direction on the plan that shapes the house, the plantings and the water.

Common mistakes

• Mapping from a single visit. A sector map drawn on one sunny afternoon in May knows nothing of the winter storm or the August fire wind. Sectors need at least a full cycle of seasons.
• Designing for the average. The average wind breaks no branches. What a design has to withstand is the rare event: the storm, the cloudburst, the fire.
• A windbreak that dams cold air. A dense hedge across the bottom of a slope can hold back the cold air flowing down at night and create a frost pocket just above it. Windbreaks on slopes should let cold air drain away.
• Blocking the welcome sun. Evergreen trees on the sunny side of a house shade it in winter as well. Deciduous trees there give shade in summer and let the low winter sun through.
• Forgetting that sectors change. A neighbour's trees grow, a new road is built, a forest is cleared. A sector map is a working document, not a picture for the wall.

Further in the TerraWiki

• Zones are the inner partner of sectors; the strongest positions are found where both are drawn on the same plan.
• Microclimate looks at what sectors do on a small scale, behind a stone, beside a pond or in a hollow.
• Base map and overlays explains how sector sheets are laid over the plan, and the design process shows where sector analysis fits in the sequence of a design.
• Element analysis asks what each element needs and gives; sectors tell it where those needs are met by the place itself.
• Swales and keyline design answer the water sector; the macchia is part of the fire question on dry Mediterranean slopes.
• Behind the tool: Mollison's design principles and observe and interact.

Sectors at Sa Medada

Sa Medada is a slope in Jerzu, in Ogliastra on the east side of Sardinia, with mild winters and a dry season from about May to September. A few lines of a sector map can be drawn from what is known. The first tree planted on the land, a service tree, went into the ground in 2024 on the very hot southern flank: that is where the sun sector bears down hardest. The LiDAR wetness map shows a comparatively dry main area with moister channels along the edges, a first outline of where water moves. In a landscape that dries out every summer, with macchia on the steeper slopes, fire is a sector that no plan can leave out.

Project Eden begins with pioneer plants, ground cover and holding water. Swales are planned; none has been built yet. Where they will run is a question the water sector helps to answer.