Green Roof Technology
So-called “Green Roofs ” are being built more and more throughout the world, especially in Germany and increasingly in the United States.
And contrary to popular opinion or conventional wisdom, they don’t have to be complicated or expensive.
Jennifer Appel is a landscape architect in Houston, Texas who had to solve a problem: how to retrofit ” an intensive green roof on a1921 historical structure.” Needless to say , the job required “knowledge of structural loading, wet weight loading, drainage, soil media selection, plant selection, irrigation fertigation and long term maintenance, while creating the design of the client’s dream requests.”
After researching different possibilities on the internet and talking with representatives of The Schundler Company, Jennifer decided on a rather new and unique soil mix: Perlite and packing peanuts.
As Jennifer wrote in an email:
“I am the Landscape Architect and Licensed Irrigator of record for this project as well as the person in charge of maintenance.
When I was researching different media sources I talked to someone at Schundler who said it would not be possible to grow trees in the mix. (FYI – it works better than soil.) Next time I have an opportunity to repeat the process, I will go more to a 50/50 and blend it during installation.
When we were installing this – the biggest problem was wind. So, we pulled (2) all nights, because the winds are almost null after dark.
Another factor to consider: the Perlite and peanuts have a tendency to float – but with about 2″ of shredded hardwood mulch – the media stays put. Do NOT use pine bark mulch – this will exacerbate the problem.
The mix is: 70% Perlite horticultural grade and 30% peanuts. The peanuts are at the bottom with the Perlite on top. The depth of the planters is 3’6 -(as a force protection barrier).
I use 1-2 minutes of water per day in the fall, winter, and spring. I use 2 minutes (2 times a day) in the summer (we are in Houston and it gets really, really hot here at mid day).
I have gone to the all organic program, feeding once a week. What we learned: All the one gallon plants exceeded 5 gallon size within 4 months. This is huge… it normally takes one whole year to get
11 of the crepe myrtle trees flowered for 11 months and 1 tree has flowered continuously and is setting new flowers right now. I have done some plant pull tests to see how well the root systems are forming on some of the plants. These plants have some of the largest and well formed root systems that I have ever seen. (I have been in the landscaping industry for over 10 years.) Hyphae, usually not visible, are extensive and the root masses are very strong. Even replacing the plants – they had no noticeable transplant shock.
I sent the same package to a hot house grower in Dallas. She had the same type of results indoors with Broccoli and all of her vegetables using the same mix and the same fertilizer.”