On the green roof there were two different sections, One section of pods had been planted as succulent garden and the other section was filled with small brush and grass had been let loose for over a year and formed a “roof prairie”. Just about every plant survived, and this semester every plant was growing. There were even one or two blooms each in the garden, but the succulent garden also had quite a few weeds coming up. To try to get rid of the weeds permanently we mixed some of the roof prairie modules in with the succulent garden’s modules. This way the smaller prairie plants would cover all the open ground that the weeds were growing in.
The modules on the roof were a lot heavier than I expected, which made me think about the overall effects of a green roof. These modules were not just heavy with dirt, but they had continued to get heavier because of the amount of water absorbed by each one. Each module’s plants and dirt absorb and retain a pretty significant amount of water. The plant, dirt, and other materials were all measurably heavier than when the modules were first planted and just about all this additional weight comes from water. I have always thought that South Texas could really benefit from more green roofs because of this quality. A single green roof can absorb a large amount of water that would otherwise become runoff, which can significantly decrease an areas risk of flooding. I think that flood prone areas like Houston could use green roof implementation to help lower floodwaters. Obviously that is a big statement to make, but spending time on a green roof and getting familiar with what it is made of has made me really believe in the stated benefits of these roofs. The first time I heard that a green roof can reduce a building’s electrical consumption by 50% I thought it seemed a bit exaggerated. Now I can see from taking apart and carrying these modules that the dirt and plant material is a really substantial barrier, that I am sure provides excellent insulation.
Just the growth of the plants alone is extremely substantial. It was amazing to see how strong and thick the roots of some of the prairie grass became. When we took apart a module we saw that the roots had wrapped so tightly around the bottom of the module that the letters of the manufacturer were imprinted into the roots. These roots also tore multiple holes through a cloth that I couldn’t even cut with scissors. I always thought that grass was kind of puny, but this grass was nothing to mess with. Even though this grass was tough it was definitely struggling to survive on the roof, the grass was more grey looking than green, and the roots wouldn’t have been so concentrated on the bottom if they hadn’t been looking for more water. It is defiantly difficult to find plants that can thrive long term on the roof. Even though the amount of soil in each module is far from insignificant, the roof provides a limit that the ground just doesn’t have.
After all the experiences of merging the prairie and succulents together, the roof seems to be doing well, and it looks like for the first time that the weeds are outnumbered by the plants we planted.