The edge is always an exciting topic amongst permaculturalists, but it’s also one that can sometimes feel a little abstract. Look on the permaculture forum and there will be a lot of folks waxing poetic about life at the edge, but like poetry (and life), it’s very difficult to decipher what it all means.
In broad terms, the edge is the interface where two biological mediums meet, and an ecotone—a less used bit of jargon—is the area defined as the transition space where those two mediums converge into something different from either one of them individually. (Well, that clears it up, doesn’t it?) This interface and transition space are often represented by things like the perimeter of bodies of water, where the ebb and flow of the shallows mix with a surrounding forest or grassland.
In these spaces, we can find more life. There is a higher population of animals, both aquatic and land, as well as thriving, thick plant-life. And, there is also an entire collection of flora and fauna specially adapted to live specifically on the edge, as seen with amphibians or rushes. The “edge effect” takes advantage of both mediums, as well as creates third in the ecotone, and that makes a space very inviting for a lot of living things and often a settling spot for moving, inanimate objects, such as wind-strewn leaves or silt.
But, the edge isn’t just the meeting spot of water and land. It can be where rocks emerge from the earth. Ever notice how the area immediately around that rock has thicker vegetation and is more likely to have animals nesting or resting. Or, it could the opening in a forest, say where a large tree has fallen and cleared space in the canopy, so suddenly birds can flitter around the edge of the forest, new seeds can find sunshine, predators can stalk along the shadowy edge of the jungle as prey enjoys the open spaces for foraging.
Extending the Edge
Now, as permaculture designers, the goal then would be to take advantage of this natural phenomenon when we can. In this sense, we are not fighting with nature, removing that boulder from our field, but rather taking advantage of the edge effect it creates. The boulder becomes an opportunity, a starting point from which we can extend a garden, creating more edge.
Additionally, we can use this with regards to man-made spaces, like the verge along a pathway or road or the side of a barn. Here we can find ecological niches, small microclimates to be taken advantage of. The wall makes a great surface upon which vines can climb, and it will also stop wind-swept nutrients or rain so that they congregate right at the edge where the wall meets ground. Birds will perch along the roofline, fertilizing, in between hunting out insects. All things converge there at the edge.
When we recognize edges, both those occurring naturally (as in the banks of stream or the adjoining of a forest and a prairie) and those put there by us, we can create beneficial systems around them, which is great. But, knowing this opportunity lies in these interfaces, we can also design to create more of them, say putting that boulder in our garden so that we can utilize the edge effect. We can also see similar ideas in urban gardens, such as planters along window ledges, trees espaliered against fences, or vines crawling up posts.
We also have the ability to extend the edge. By making our designs more amoeba-like in shape rather than straight lines or perfect geographical patterns, we can greatly increase the amount of edge. Classically, we have seen instructors take a circular pond and shape it into something more akin to a paint splat. This extends the banks of the pond, the edge, immensely, maintaining the same area but increasing the perimeter. Similar, we can shape our beds, patios, pathways, and food forests this way, with undulating borders.
Defining the Edge
Lastly, in our designs, by defining the edges, we can established what benefits we’d like and/or available to us.
Firstly, within our garden beds, where we have created edges, such as our purposefully placed boulder or perhaps a tree stump, we should be working to take full advantage. Planting near them, where water and nutrients and warmth and beneficial animals congregate, will help our seedlings and sapling spring up successfully. Creating plenty of internal edges within our beds can signify the most fertile spots to plant. We can also get vertical with trellises, creating different types of edges with edges.
On the outsides of beds, we should also make the effort to establish clear and extended edges. Logs along the downside of swale on contour can help provide habitat for beneficial animals, capture nutrients in our growing space, keep mulch in place, and make it easier to hold weeds at bay. Or, this could be done with bunching plants, like lemongrass or perennial bunching onions, or dynamic accumulators, like comfrey and borage, which can be chopped periodically and applied as nutrient-rich mulch. Rocks work, too. Once the edge is defined, we can begin cultivating and maintaining our gardens more appropriately.
Then, it’s a matter of appreciating the diverse microclimatic and structurally stabilizing effects created by all these extended edges. Has a raised spot given shade to a particular side? Does organic material accumulate in one of the inlets of that amoeba shape? Has a frost pocket formed somewhere? Can a productive hedge of berries be planted along the outer reaches of a food forest, a collection of herbaceous groundcover along the bottom edge of the hedge? Will a corner formed by two walls be a perfect little alcove, protected from the wind, for a tree? Or, is that corner dank and moist and yearning for something like banana or bamboo? Is the edge of the patio, where rainwater runs off, an ideal spot of water-hungry plants?
Once, we can define the edge clearly, see just how it is working and how we can work with it, options abound.
Feature Photo: Raised Terrace Edge (Emma Gallagher)