The use of natural patterns in permaculture was brought to the front of my mind when recently I re-encountered the beautiful drawings of Ernst Haeckel after they had been released into the public domain. Haeckel’s drawings of diatoms, jellyfish and other facinating organisms are intended to provoke us to consider questions of order in nature by their astounding symmetries. I was struck by how many of them possess variations on the classic “keyhole” pattern suggested by Bill Mollison for garden access. One panel in particular could almost bear the title “Meditations on the ‘Keyhole Pattern’”. These drawings provoke the questions which must be asked of all patterns if they are to be useful in design — why are they like that? To what problem are they a solution? By what force have they been shaped?
The patterns of the natural world play a prominent part in the design practice of Permaculture. Too often though natural patterns and shapes (spirals, curves, waves, branches etc.) are used as if they were magical — as if “naturalness” was a sufficient condition for their use in design. This use of pattern can serve an aesthetic purpose but in what other ways are natural patterns useful to designers? I would like to briefly explore a different approach to patterns through looking at the keyhole path.
I would like to begin this exploration with a quote from Mollison on the application of patterns. He writes:
"There are two aspects to patterning: the perception of the pattern that already exists and how these function, and the imposition of pattern on sites in order to achieve some specific ends." — Bill Mollison, The Permaculture Designers’ Manual, p. 95
Haeckel’s drawings inspire thoughts of both these approaches — They remind me of the keyhole, a form of pattern imposition ‘to achieve some specific ends’. If you were to place a tree in their centre, some of Haeckel’s drawings would be a ready representation of a guild planting in a forest garden with ideal access. I am also provoked to think of what forces and conditions influenced the particular organisms to possess these shapes. For now though I will leave reflections on this latter approach for a slightly more geometrical approach to the question of what problem keyholes solve.
What is a keyhole path? A keyhole path is a solution to the design problem of access. It is perhaps best described by comparing it with another similar design solution to the problem of access — the linear path. Let’s assume that we need access for a person only, not a wheelbarrow, and so set path width at 60cm. Let’s also assume that an adult can reach about 70 into a garden bed while kneeling on the path and that the garden bed has a length of 2 m. Given these assumptions, a maximum garden bed with of 1.4 m (70cm reach from each side) can exist between two paths 60cm wide. This makes for a total area of 5.2 m2. The linear paths occupy 46% of this space. By contrast, a keyhole bed with a 1m diameter circle at is extremity takes up only 26% of the available space while still allowing full access to the garden bed.
Keyhole paths mimic the natural pattern which occurs, for example, in the human lung and many other places where folds or ‘crenelations’ are the solution to the need for increased surface area. An increase in surface area increases the capacity for exchange across a boundary. A keyhole allows for a high degree of edge between path and garden while keeping the space required for the path small. In our comparison, the edge between path and garden is approximately the same for the linear and the keyhole path but the keyhole occupies 20% less space.
In short, a keyhole provides access while minimising path space (ie. maximising garden space) and creating a large surface area between path and garden. A keyhole is also an end node for a branching pattern but that is a story for another day. In the mean time, have a look at Ernst Haekel’s pretty pictures on wikimedia and lift your hands the god of the public domain.
- The Encyclopedia of Life: Pediastrum
- Wikimedia: Beautiful Haeckel drawings from Kunstformen der Natur