Green Roof Experiential Learning – Spring 2015 Blog 3 Hort Students Condensed

By Martha Todd:

In the past two weeks the plants have started to arrive and thus the dirty work begins! We began by categorizing the plants that had come in by which wall they were assigned to and then to the different types of holding containers. Wall 1 has containers that hold 6 plants each while wall 3 containers carry 16 plants. The next step was to create the soil mixture to put in the modules with the plants. The soil was a mixture of mulch, rocky and sandy dirt, and added nutrients in the form of beads.  After this was completed we planted everything that had come in and continued to do so as new plants came in on different days.

During the last class we weeded the plots that were located on the roof ground and planted tomatoes and bell peppers, typical summer crops. The plants that grow from these ground plots are typically very healthy and produce an abundance of fruit and vegetables so it will be interesting to see if the same pattern is repeated for the summer crops that were just planted.

My favorite part about this directed studies class was that I was outside of the traditional classroom engaged in a project that could become a common feature on buildings and houses everywhere in the country. Before I took this class I had no idea what a green or living wall looked like; however, this class has taught me about sustainability, urban issues, and basic research skills while the whole time never having to study for an exam or open a book. It’s all hands on. I wish more classes were like this one because after this class I want to focus on sustainability as a career and study more of the ways that green walls can impact energy levels, communities, and the world around us as resources become more scarce and we as students must find solutions to overcome these obstacles.


By Nicole Forbes:

The semester is coming to a close and so is this semester on the green roof! This semester flew by so quickly. I have not got to do much on the roof this end part due to finals and group projects but I still got some stuff done!

One of the things we did a lot of these past couple of weeks was mixing the old sandy, gravelly soil with fresh potting soil and Osmocote to give the new plants more sustenance and nutrition. We did two parts gravelly soil with one part fresh potting mix with sprinkles of Osmocote throughout the mixture. Hopefully this will allow the plants to grow better than the ones that were on the walls in the past.

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We also began to put the plants that we bought into the wall modules. We only did four per module even though there are eight spaces to give the plants room to grow into the rest of the module. We will be getting a few more plants in the next couple weeks and I plan to help with that also. That’s really all I’ve done in the past month on the roof. I’m looking forward to going up in a few weeks and seeing how the plants are fairing.

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By Ivan Mendoza:

The last couple of weeks we have been taking down the green walls in preparation for the new plant material coming in. Green wall 1 was taken down first. The modules were taken down individually. All the medium and old plant material was removed from each module. Once all the modules were taken down they were rinsed out and cleaned. Green wall 3 was the next one taken down. These modules were a little bit heavier and bigger than the modules in green wall 1. They were more tedious to remove due their size and structure. The medium and old plant material in these modules were removed just as well. All the old medium was placed in trash cans were fresh soil was mixed with it. Following osmocote (slow release fertilizer) was applied to the mixed soil. We used this soil for the modules removed from green wall 3.  The new plant material was inserted in each of these modules with the mixed soil.  Over the last couple of weeks we have also been harvesting any plant material that has needed to be harvested. The strawberries that have ripen over the last couple of weeks have continually been harvested. The rest of the edibles have continued to be harvested as well. We have also removed any weeds that have developed in the edible modules over the last couple of weeks. This is my last blog for the semester. I have really enjoyed taking this course. I’ve learned a lot over the course of the semester through researching and hands on application. I look forward to hearing how the new plant material does on the green walls in the summer.

Studying Abroad from China, by Zhilin Huang

I’m Zhilin Huang, a landscape architecture student studying abroad from China at Texas A&M University. My professor, Donghui Peng, back in China from the Fujian Agriculture and Forestry University (FAFU) is also in here at Texas A&M doing research in Horticulture. He has a green wall experiment program in FAFU. The goal of the program is to build a material company that uses a green wall technique for the exterior wall tiles. Dr. Peng joined a class and counted the survival rate and death rate of plants with us. After that, he gave us some suggestions about how to improve the green walls that we are working on. In my opinion there is a problem with the irrigation system in wall 2 and the shape of the modular is not suitable for adequate root growth.

Although many difficulties lay in the way, we can still learn something from the failures and go through them. Despite the hardship we experienced in vertical gardens, there are some good results in the roof garden. The vegetables grew very well and I really enjoyed the time eating the crops we took care of and harvested. Next time we will remove the dead plants and plant some new ones in the green walls.

I’m looking forward to doing them.


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Living wall blog by Zhilin Huang

In the last few weeks of the LAND 485 Special Topics green roofs and green walls course, we removed the dead plants from the old modules, and then refilled the soil for those modules. After that, we transplanted the new arriving plants to the modules and then put the modules back to the wall.

In this semester, I learned a lot from this course, and I also learned the experiments could take a long time to be tested, applied, and retested. The ideal green roof technology has a large potential market in the future.

The green wall technology will be well placed to expand in the Chinese market. In China, there are millions of people living in apartments where the private outdoor gre  en space is limited. Those residents are also entitled to the right of enjoying the nature, but it is really hard in the skyscrapers, so most of them place some flowerpots or plantings on their balconies. However, the arrangement of the flowerpots is usually the same and very boring, some people don’t have time to walk into their balconies and cannot take enough care of them. It might because the flowerpots in the balcony are far away from people’s daily activities area and residents in China prefer to use balcony to dry their clothes. Although this may be the common problem, we can still use some simple equipment to build a green wall at home by ourselves. The reason why green walls are going to be popular in China is because green walls can utilize the vertical space instead of horizontal space in people’s homes. So they would like to have green walls in their balconies, either designed by themselves or by the real estate developer.


Plants arrive and are unpacked.


Plants are inserted into modules and hung on wall.


Plants inserted into large module.

Plant Identification for Green Walls by Zane Pace

One of our first tasks this semester was to identify potential plants for replanting two of the modular green wall systems in our experimental setup. Last year, we replanted wall 2, the one with the pockets I dislike so much, and now it is time to select plants for walls 1 & 3. I’ve found that I enjoy the process of researching and identifying potential plants for use in green roof and wall systems, so I wanted to use this space to enumerate some of the more crucial aspects of the process. These include characterizing the site, identifying required plant traits, and then searching for a match.

The first step in the process is identifying the microclimate that the wall system will inhabit. In our case, since we are working on walls installed on the exterior of a building, the regional climate plays a large role in this. Many living walls you may see on pinterest or wherever may be inside buildings, and for those, local exterior conditions may not be as important. In our case, however, it is important that the plants are hardy enough to survive in the climate of central Texas. That means USDA Hardiness Zone 8B.

Microclimate, of course, implies that there are smaller-scale climactic variables that affect the walls. These include things like sunlight and wind patterns that are affected by the built context of the site. All of our systems are mounted on the south facing walls of a rooftop enclosure on top of the Langford architecture complex here at TAMU. The other walls of the enclosure provide wind shelter for the site, but also affect levels of shade throughout the day.

All of these considerations are further refined by the differing designs of the systems themselves. These vary in terms of plant positioning, substrate depth & composition, and irrigation design. For example, Wall 1 uses modules with 8 compartments that project out from the wall at a slight upward angle, maybe 30 degrees. The slots in bottom dividers allow irrigation to trickle down from module to module, and the plants grow at an angle. This would seem optimized for plants that are commonly grown in pots and tend to produce foliage that cascades down. Unfortunately, the slots only go part of the way down the module divider, and the bottoms of the compartments often fail to drain and can get waterlogged. Therefore, moisture tolerant species may be necessary. Wall 3, on the other hand, uses large, boxy modules that each hold one large bag of substrate. There is no angle in this system, and also no dividers within the modules. This provides greater nutrient access for plants, but also allows greater competition among species, and requires they grow straight out from the wall.

Having characterized the unique concerns of each system’s microclimate and gained a sense for the constraints that plants will have to cope with, we can develop out some desired trait parameters and go research. I primarily did this using the database that allowed me to sort plants based on criteria. For example, Zone 8, full-sun, perennial, 0-18” tall, and moist-wet soil tolerant. Then one can sort through that entire list for plants that combine those characteristics with aesthetic appeal. Sounds a bit boring, right? It is.

What’s more fun is to go out into the community and identify plants already growing in sites with similar microclimates to the roof. This is the ‘go out in nature and find plants growing I those conditions’ method, and I did it constantly on a recent trip to Spain. In Valencia, I encountered several plants in environments that made me think. Valencia sits astride the former riverbed of the Turia river, which was diverted mid-century because it kept flooding. The entire riverbed was converted into a park that basically runs the length of the city. It’s cool.

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When the entire park is probably 15-20 feet below street level in the city, and as such, the former riverbanks are now large walls that simulate the environment on the roof quite well. The park and street level are connected by long ramps, the sides of which are more intentionally vegetated, but also steep and providing a natural comparison to our site. I found numerous plants growing in a crack in the wall or tumbling down the side of an embankment that I thought resembled our wall environments.

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The first one is growing out of the side of the embankment, the first is just popping out of the side of a bridge.

These discoveries not only gave me plant ideas, they also helped me identify useful characteristics I had not considered, and helped refine my search process. Seeing plants growing in nature also sheds light on how people relate to the species, on the subjective experience of interacting with that plant. This is an important consideration, as the human impact of green roofs/walls is just as important as any environmental or resource efficiency benefits they impart.

Green Roof Food Productivity by Variety by Zane Pace

Our focus this month has been on harvesting the winter crops we planted last semester, and identifying our top performers. Plants were harvested continuously over several week period, sorted into marketable and non-market categories, and weighed for biomass. We generated data on establishment, survival, productivity, and marketability % for each crop. I was fortunate enough to be allowed to analyze the data myself, and to present our findings with Nicole Forbes at Texas A&M’s Student Research Week this year. Unfortunately, it turns out that I get maybe a little too into data analysis, and SRW posters only allow for the presentation of so much data, so a lot of the graphs and comparisons I churned out wound up not getting included. Fortunately, I know just where to present the bits I had to omit from the poster. Here.

First, I’ll give you a quick and dirty posterview (portmanteau of poster and overview, duh) to relate the general results. From a survival perspective, everything was pretty positive, with the exception of root crops like turnips and beets. Leafy greens and herbs are definitely viable for green roof production. Of those we were able to harvest for this data, Kale, Lettuce, and Parsley were the most productive. What I didn’t get to include, however, was the variation among different strains of these crops, which was considerable.

While we looked at the overall crops for their productivity, each of those includes several varieties, each of which produced at different levels and fared differently on the green roof. I can’t be sure why this was the case, but the intracrop productivity splits were apparent enough that I wanted to investigate them. I did so by charting the relative contributions to a crop’s total marketable biomass by each variety, or varietal market share.

Lettuce provides a nice starting point, because it displayed a very even varietal split. With only two varieties, it is also the most basic case. We planted the same number of both Butterhead and Romaine lettuce, and establishment was identical for each. They each produced about the same amount of marketable biomass too, so the split is almost 50/50. This is expected.


Parsley getting a little less even

Parsley exhibited a slightly different share split. 3 parsley varieties were planted, including Italian Plain, Curly Leaf, and Italian Giant. Of these, the Italian plain produced 50% of the marketable biomass, while curly leaf and Italian giant generated 28 and 22 percent, respectively. I don’t have an explanation for this difference, but it is a significant split relative to that seen in lettuce.

What is Red Russian Kale doing with its life?

The Kale is the one I really want to discuss, however, because it has an extreme varietal split. We planted Beira, Toscano, and Red Russian kale varieties. All of them grew and survived at high rates. However, beira kale produced a full 73% of the marketable kale biomass from the roof, while red Russian accounted for only 5. Toscano was 22%. Part of this split is due to differences in leaf size and shape among the varieties. Beira grows wide, large leaves more similar to those of lettuce, while red Russian and toscano produce the long, slender leave you might typically associate with kale. Hence, Beira leaves just account for more biomass. However, the splits were further driven by flaws in the other varieties. Only 28% of the red Russian was marketable, compared to 73% for beira and 98 for toscano. The reason for most of this was bugs. Red Russian kale leaves that were otherwise perfectly fine had to be rejected due to the loads of aphids they attracted. Aphids that didn’t appear on any other plants on the roof. I have no idea why these bugs seem to love red russian kale alone, but they seriously compromised large proportions of an otherwise fine harvest, and should be accounted for in any future green roof farming projects.

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.

Green Roof Experiential Learning – Spring 2015 Blog 2 by Nicole Forbes

Spring is here (well as close as you can get to spring here in Texas) and with it has come a revival of plant and crop life! The mint has come back with a vengeance and some of the other plants that were looking dreary are greener than ever!

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Zane and I presented our green roof crop research at Student Research Week the week after Spring Break. It was an awesome and rewarding experience. It gave me experience both in poster making and presenting research to a group of judges, I hope this experience will help me in future research presentations.

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Other than Student Research Week, we have continued harvesting and have begun to take down the living walls. There is not too much to report this time, but we will be redesigning the living walls and planting new crops and plants. I will also be looking after the crops over the summer after I get back from a month trip to Costa Rica! I’m looking forward to finishing the semester out!

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Green Roof Experiential Learning – Spring 2015 Blog 2 by Martha Todd

Three weeks ago we harvested some of the crops that had grown on the plots of dirt on the roof of the building. Many of the spinach and parsley plants had a bountiful harvest and much of what we measured was marketable with little defect or holes in the leaves from insects. After the measurements were recorded the team and I began to record the number of plant species that were still living on the three walls. Most of everything was dead as we think the plants may have received too little irrigation. However, all of the succulent plants on the first wall were surviving, not thriving, but indeed were all alive.

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On April 10th the team and I learned what species of plants we were receiving for the living walls such as Mexican Petuna and Japanese sedge. Depending on the cost of the plant, the availability, and the predicition that certain plant species may thrive better than others, we ordered more of certain plants than others. After deciding the quantity of each plant, our next business was to decide how they would be arranged on the wall. For wall 1, we decided to go in an organized pattern for 5 plant species making sure that one of each plant species was placed on each horizontal and vertical row. The resulting pattern was one of diagonal stripes by the time we had completed the placement. For wall 3 we decided to follow the same pattern with a different set of 5 plant species, however, we then randomized by switching the order of the rows and columns to make sure there was a degree of randomness in plant order. Wall 2 has not been decided on yet. In the next month as the plants begin to arrive we will begin planting them based on the diagram constructed and see how they flourish. Questions we will be looking to answer are: Does placement on the living wall correlate to the ability to thrive? How do some species respond to the irrigation system verses others?

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Wall 1 in the background and showing the height parsley has reached.

Green Roof Experiential Learning – Spring 2015 Blog 2 by Ivan Mendoza

The last month we have seen a lot of our edibles bloom out and flower as well as produce edible fruit/foilage. All the wildflowers and bluebonnets around Texas A&M University campus have blossomed as well during this time period. We have recorded the marketable biomass data of our edibles over the last several weeks. Our colleagues within the greenroof course have presented this data during Student Research Week to judges, students, among anyone who was interested. We have collected the most marketable biomass from Lettuce (Butterhead) the past month. The following is the rank for the amount of marketable biomass collected from the edibles: Lettuce (Butterhead): 2458g, Kale (Beira): 973g, Parsley (Italian Giant): 779g, Parsley (Curley Leaf): 309g,  Arugula:  300g, Kale (Tuscano): 300g, Broccoli (Arcadia): 242g, Spinach (Emperor):  168g, Radish (Easter Egg): 122g, Kale (Red Russian): 60g, Cilantro (Chinese): 56g. The last week or so we have continued to keep the modules free from ants and weeds to encourage maximum growth for the edibles.  We also have started bringing down the plant material on living wall 1. We will bring down the rest of the plant material on living walls 2 and 3 except for the succulents, strawberries, and any other material that looks alive.

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Once the new plant material comes in, we will plant them in the modules and bring down the old plant material. We will be planting warm season edibles.

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Indian Blanket has bloomed along with the succulents the last couple of weeks.

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