Working with green walls, variation among systems by Zane Pace

The tail end of the semester has seen the arrival of plants we ordered to replace the walls and winter food crops, and more hands-on work with the systems themselves than we had previously undertaken. That means taking down the systems to install new plants, which has afforded us wonderful insight into the design of the systems and the amount of work that goes in to plant establishment and preparation for a green wall. This experience could prove invaluable as we look to design more efficient systems or expand them in scale, as it provides a look into the technologies and structures that facilitate flows of energy and nutrients in artificial ecosystems.

One useful aspect of the experience is the chance to work with multiple wall systems. There are three living walls included in our experimental setup, each with its own unique design and microclimate. I’ve written about these before, but I’ll review anyways. Wall 1 consists of modules angled upwards, out from the wall, that are divided into 8 plant compartments each. These provide a not exactly horizontal growth environment for the plants. The modules for wall 2 consist of 3 rows of 4 felt pockets, each holding one plant. These units are larger, and would be difficult to remove, but allow plant care can be carried out on an individual pocket basis. The soil reserve is vertical, allowing plants to grow more-or-less vertically. Wall 3’s modules are large, rectangular plastic skeletons that hold bags full of growth medium and plants. They are definitely the heaviest module to interact with, and also more difficult to replace the plants for. They also require that plants grow basically horizontally out from the wall.

Wall 1, Modules on the ground

Wall 2. The problem with pockets.

Wall 3: modules establishing

Working on three unique green wall designs side-by-side reveals the relative strengths and weaknesses of each design. Opening them up and pulling them apart allows us to infer the strategies that informed each design decision, and presents a collection of alternatives. The walls have been in use, “functioning” to various degrees, for something like a year or more prior to this replanting, meaning we know which aspects of a given system aren’t performing optimally. Through the replanting process, we’ve been able to see behind the green wall and appreciate the design of the various irrigation systems to a degree not possible when those systems are embedded behind a bunch of plants. We can start to trace the causes of any deficiencies in these systems, and have several alternatives on-hand to compare.

Since we took the modules down to replant them, they have largely been left to establish off the walls. This is in part because some systems recommend an establishment period of several weeks prior to hanging the modules on the walls, and in part because plants arrivals are staggered and we need to hang all the modules at once to implement our design. Comparing the systems during establishment sheds light on their effectiveness and how they could be improved, but more than that it highlights an important consideration for sustainable and biophilic design. That is time.

It takes considerable time for any natural system to establish and develop. It is important to remember these time-scales when we think about sustainability, whether in terms of projects or in terms of developing sustainability at a social level. The establishment of a green roof or wall is an evolutionary process, and so is the establishment of a green society. We have to let the strong root structures that can support such a society develop and then spread throughout the substrate of our culture before we proclaim it ready to hang up and call done. The diffusion of the ideas and technologies that will drive a sustainable, global human civilization takes time, and we must be understanding of those who lag behind. It is easy to grow discouraged about humanity’s prospects when we see parents and role models ignoring the signs that we must move towards sustainability, carrying on with ecologically profligate lifestyles. But that disappointment stems from the same desire for instant gratification that got us into this mess in the first place. We must start playing the long game ourselves, if we want society to follow us and do the same.

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