Green Roof Experiential Learning Blog 2

And we also added new nine modules for growing proposed crops. In making the substrate and filling soils in the module, firstly we put a layer of substrate to fill the holes in the modules, and a square blanket was used to cover each modules on the top of substrates. And soils for growing vegetation are put on the top of blankets. The texture of substrate soils is coarse which can contribute to positive drainage within the modules and the texture of topsoil is finer than substrate soil and it is opulent with organic matter and water content.

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Then the most interesting part came! The transplanted and seed crops arrived, which included Arugula, Chives, Cilantro, Mint, Shallots and so on. Prof. Merrill helped us arrange the layout of different crop species and we took off the outside plastic packings of transplanted crops, burying the roots under the topsoil. Talking about the most difficult part, I think it is to install the irrigation system. I didn’t participate in that part, but I saw my teammates tried to connect the pipe with water source, cut the pipe according to the dimensions of modules, used nodes to connect pipes with chemical glues. Finally, four irrigation nozzles were set up around the crop modules. The nozzle radius is suitable for the site, but one full-nozzle should be replaced with half-nozzle.

Another type of plants we want to grow is succulent plant. So we also had a discussion about the appropriate species for roof planting and before that we each people had a suggestion list. I proposed 6 succulent plants, and I feel so honored that 4 of them had been chosen for growing on the roof, which include Sedum palmeri, Graptopetalum paraguayense, Opuntia cacanapa ‘Ellisiana’, and Euphorbia resinifera. Many other succulent plants are also proposed, such as Nolina macrocarpa, Hesperaloe parviflora, Sempervivum ‘Carmen’, and Agave colorata x parryi and so on. We spent much time on arranging and distributing them in a well-organized and good visual-effect way. We made the short plants as ground cover distributed around the tall plant in the center. The same species are arranged together forming a group.

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Green Roof Experiential Learning Blog 1

My name is Chenni Zhu, a third-year MLA student. On the first day we went up to the roof garden, what we were required to do is to remove invasive weeds and pick up mature fruits of some crops such as tomatoes, shallots in the nine modules on the ground. Then we need to weigh the fruits from crops and record the numbers. And I feel what a pity that most of crops grown on the roof in summer are dead for these one or two months. It may be due to the harsh weather which is too hot and dry without frequent precipitation in Texas.

So on the first day, we almost removed all of the weeds in the nine modules. However, what we saw in the next week surprised us that many weeds had grown up again in the modules due to a rain in that week. Thus, we had to weed them again to ensure there is no chance that these weeds would come up again. I have to say that the invasive weeds are really strong and capable of establishing themselves in prevailing conditions without manual intervention, while we should take more care to crops.

After weeding, we were required to discuss what kinds of crops are capable of living on the roof top and surviving well. A study about “Assessing Crop Viability for Agricultural Production on Extensive Green Roofs” provided us with some statistics about which crops are suitable for growing on the roof in Texas. The evidences showed that the strong survivors (80 %+) include Chives, Cilantro, Parsley, Thyme and Mint among transplants. Moreover, among direct seeded crops, strong survivors include Arugula, Garlic, Kale, and Shallots. On the other hand, every team member was required to provide a list of suitable crops for growing on roof. So based on the study and the information I collected, I think the Arugula, Chives, Cilantro, Mint, Shallots and Thyme are ideal crops surviving on the roof. After that, we discussed the final crop species and basic layout of them according to the visual effect of combination of crops, the different demands on water amount of different crops, and numbers of crops.

Below shows the later situation of some crops we grew on the roof. Most of them are in a good condition.

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Vegetables, Cable Ties, and Hose

November’s goals could not be pursued without Succulent Garden weed control.  A typical rooftop day sees the class split between weeding, collecting inventory/harvest data, or adjusting the irrigation system.  The Vegetable Garden’s rapid growth and lush color presented an image … Continue reading

Then and Now


By Nancy Luong

We have made lots of progress ever since we first started the project. The rooftop was barren when we first arrived on the roof in September, and now it is a thriving work in progress.


Looking at the same area side by side in two month’s time really shows you our progress, and how much work there is left to do. But I am hopeful that these plants will flourish come spring and fall next year alongside the green walls.

In the very, very beginning back in September we propagated plants and did so every so often throughout the months. As an environmental studies major, I do not know much about plants, so this was a new experience for me. I didn’t know that root hormones were used to make new plants. I thought that the plants bred on their own with seeds. A week later we installed the membrane, and the following two weeks were spent on installing the roof tiles. They are tough ones to push together and install properly! We had to use hammers, planks of wood, and brute kicking force to get the tiles as close as possible together.

Starting on the second week of October, we started working on our modules. These modules are plastic and have gravel as the drainage medium. On top of the gravel is a filter layer, and roof media sits on top of that. The filter layer is to keep the roof media from leeching out into the gravel layer where it can escape through the holes in the module. The team divided up into three lines. One worked on assembling the modules with gravel and the filter later, another worked on filling the module with the roof media outside because there was lots of dust, and the last group loaded the trays onto the roof. Often times, we were short handed and had to do all three parts, but it was not a big deal.

We assembled all of the modules on top of the roof by the first week of November and started planting then. The installation of the irrigation system took place when I was not present. Now is the end of November and the beginning of December, and the current state of our roof is still a work in progress. On November 30th, my group went up to the top of Langford and made our contribution. This day of planting was no different than the previous ones because we were working with the same species. The only difference is that we were planting bluebonnets! I heard from two separate students, Greg and Tess, that these flowers do well in poor soil so we should see the beautiful blossoms soon enough. I also heard from professor Dvorak that one of the species is aimed towards bringing butterflies to the rooftop. In fact, while we were planting, a nice white butterfly paid us a visit.


I have gained experience in the amount of effort it takes to create a green roof and about plants during my time in this directed study. There are no other classes I could take that would come close to this type of hands-on experience, so I do envy the students who will take the course next semester and build upon what we started. One day I hope to come back and visit the green roof in hopes of seeing a luscious garden!