Growing a green roof at the Pittsburgh Zoo & PPG Aquarium: part two

June 10, 10:25 PMPittsburgh Gardening Scene ExaminerRose Field

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The green roof atop the Zoo's Water's Edge Building photographed by Susan Pierce

In the last Pittsburgh Gardening Scene Examiner article, we spoke with Susan Pierce, gardener at the Pittsburgh Zoo and PPG Aquarium about the benefits and challenges of creating the innovative green roof atop the Zoo's Water's Edge Building.

Sue described how one side of the green roof installation is referred to as an intensive green roof with a soil depth ranging from 4” to 3' deep, while the other side is an extensive green roof with a soil depth of 3”- 4” and different mineral and organic soil components.

Q.: What particular objectives did you have in choosing the plants, such as tolerance to wind, sun exposure, etc.?
A.: For the extensive side, I chose a lot of “prairie plants” native to the western part of the country that can withstand harsh conditions like the ones mentioned. Also I included some native western PA plants that are acclimated to our area. On the intensive side, I chose many traditional perennial plants but took care to choose the ones more tolerant to dry, sunny, windy and cold conditions.

Q.: What successes or failures have there been among the plants chosen?
A.: Almost everything survived the first year as well as the second. Of special mention, the Knockout Roses, Agastache, Penstemon, Rudbeckia, Ornamental grasses, Sedums, Microbiota, Rudbeckia, Caryopteris, Coreopsis, Asters, Aurinia, Stokesia, Cerastium, Origanum, Thyme, Cornus Kousa , Heptacodium, Salvia, Lavenders, and Armeria performed beautifully. We’ve lost 4 of the 14 research plots, namely, Hymenoxis scaposa, Campanula cochlearifolia ‘Bavaria Blue’, Stachys coccinea ‘Chinook’ and Lewisia longipetala ‘Little Plum’. We also lost a Caragana pygmaea, which being on the intensive side, probably needed less irrigation then the other plants it was planted near. Everything else seems to have endured, if not flourished.

Q.: Tell me a little about the roses you used.
A.: I’ve planted the rose variety ‘Pink Knockout’. It has performed beautifully. It is highly disease and insect resistant. It can withstand the harsh conditions of the heat, wind and cold on the roof.

Q.: Has the Zoo realized savings on heating or cooling since the green roof was installed?
A.: I'm sure we have, but there was no data collected on the building before the green roof was installed. We have nothing to use for comparison.

Q.: Do you plan to implement a green roof on any other buildings?
A.: I'm sure it's in the planning stages, but nothing is definite.

Q.: Sue, you have an extensive background as a horticulturist, having worked at Pittsburgh's Phipps' Conservatory. Would you list your experience?
A.: I was at Phipps about 5 ½ years, and then worked as an estate gardener for three more. I've been at the Zoo thirteen years.

Q.: A modern facility of the quality of the Pittsburgh Zoo and PPG Aquarium obviously has extensive plantings providing the animals with the best possible habitats. I noted from the Zoo's website that it covers 77 acres. How many gardeners work here?
A.: There are 3 gardeners. I take care of the 2 interior rainforests at the zoo - one in the Tropical Forest Complex and the Amazon Rainforest Exhibit in the aquarium, the exterior of the Tropical Forest complex, the gorilla yard, an off-exhibit greenhouse and the green roof on top of the Water's Edge/polar bear exhibit. My 2 colleagues take care of various outdoor areas.

Q.: Phipps' Conservatory is now renown for innovative green building practices. How does the Zoo compare and do they plan on becoming even more green?
A.: The zoo constantly strives to be ‘green’. Conservation is one of the zoo’s main missions. I’ m sure all future buildings and exhibits will be built with ‘green practices’ and green materials in mind. We have a ‘Green Team’ comprised of employees from various departments. They meet regularly and constantly look for ways the zoo can conserve energy and recycle the products it uses. An example of this is we have switched all of our cleaning products to green seal certified products. Also the Horticulture Dept uses environmentally friendly pesticides like isopropyl alcohol, soap, soybean oil and beneficial insects to control pest problems.

Q.: While I realize that the green roof was installed for all the ecological and cost savings benefits we talked about and for research, and is not open to the public, is there a chance that visitors can catch a glimpse of it? With the Zoo being laid out on a hillside, I would think people could look down on it from above at some point.
A.: About the only place the general public can see the roof is from the public path where the Spectacle Bear is located. If you look through a gap in the privet hedge, you can look across and see the green roof. I hope to have a sign in the next year or so to call attention to it.

Take a peek at this amazing green roof on your next visit to the Pittsburgh Zoo and PPG Aquarium. For more information about the Zoo, along with directions and hours, visit the Zoo's website.