Gardens on Tour 2007: Stratus green-roof garden
I’d never seen a green roof before, and as this is the first one in Austin I didn’t want to miss my chance. So mom and I drove down to southwest Austin’s Circle C neighborhood, which is near the Wildflower Center, the sponsor of this tour and a member of the project team that installed the green roof.
Built on the second-story roof of a Starbucks located in a strip mall in the neighborhood, the garden is designed to be seen from the inside of the coffee shop. I should have looked at it from that vantage point too, but I didn’t think to, and anyway, it was fun to see it from the roof itself, which is ordinarily closed to visitors.
Since I know zip about green roofs, I’ll share the information from a handout I received:
The 8,000-square-foot planted roof fulfills a function that goes beyond novelty. This extensive green roof is the first in Texas and one of the first in the U.S. to feature an entirely native plant selection. Flowing masses of native grasses, sedges and perennial wildflowers direct the eye to a sea of prairie.
The 2′ x 4′ x 8″ modular green roof tray system was chosen to provide flexibility in the roof configuration of the commercial retail center. Run-off from the roof is collected in rainwater harvesting cisterns and used to irrigate the surrounding landscape. The green roof was installed in October 2005 and is a part of a City of Austin research project investigating green roof technology and application in urban stormwater management scenarios.
Pretty nifty.
The garden receives 3/4 of an inch of irrigated water weekly, a docent told me. Mexican feathergrass dominated the scene on this day, undulating across the roof in the breeze. I saw tiny pavonia coming up in some of the other trays, and other plants listed include skeleton-leaf goldeneye, agarita, damianita, crossvine, Virginia creeper, nolina, and various muhlies and sedges. I’ll have to go back and view it from inside the shop at other times of the year.
The view from the exterior stairs. As you can see, these plants have to be super tough to make it under Texas’s blazing summer sky with no shade, shallow soil, and strong winds.
Also today, tune in for a tour of the Skyline Drive garden. Tune in tomorrow for a tour of the Bridle Path garden—the best of the bunch.
If you would like to see another impressive green roof there is one in Salt Lake City on the roof of the LDS Convention Center. At the same time a visit to Red Butte Gardens on the University campus is a fabulous native garden.
Thanks for the tip. I need to make a list of these places to visit in different cities in case I ever find myself traveling through. —Pam
Pam, thanks for linking to this. Question: I thought “extensive” meant without irrigation, so am surprised they use that term for this Starbucks roof. I visited greenroofplants.com in Maryland and they gave me a poster called “Extensive Green Roof Plants,” and it’s all sedums except for one Jovabarda. The poster’s now displayed on my office wall and is SO handy to refer to as I type this.
That’s a good question, Susan. I didn’t even know that definition of “extensive.” I’d thought it meant, simply, “large.” However, a quick web search turned up a looser definition of “extensive”: “Extensive green roofs require only periodic maintenance. Plants may need to be irrigated during the establishment period, usually for 6 months, and only if natural precipitation is insufficient. On a large roof, it may be economical to lay drip irrigation tubing during installation to allow for uniform watering during establishment and in occasional periods of extreme drought.”
It’s hard for me to imaging anything living through a summer on an exposed, shallow-soiled Austin rooftop without a little supplemental water, but maybe it can be done. —Pam
Only sedums can take that kind of neglect, according to the greenroofplant guy – Ed Snodgrass – and are sold for roofs without irrigation.
Thanks Pam. That Mexican feather grass is pretty by itself but with a few flowers and tough vines it would be great to view.
If I’m ever in Austin that sounds like a destination.
Yes, it would be worth a look. So would Austin City Hall, which has a green roof over a lower section that you can see, as well as a pretty native-plant landscape and stonework. —Pam
Red Flag Warning for Green Roof Designers.
With serious drought often in place in central Texas, prairies can burn wildly, causing losses to human and animal life as well as property. The green roof installed at Stratus Properties’ Escarpment Village is comprised of ever so flammable native prairie vegetation.
While green roofs certainly deserve a place in modern Austin construction, they do their important job of cooling and purifying the city precisely by being green. Native prairie selected by the wildflower center environmental designers naturally turns brown in winter and is designed by nature to burn periodically. I hope customers at Starbucks won’t mind scalded milk in their lattes.
A restored native prairie might make a nice landscape feature in Austin, but it’s a poor choice to do the job of a green roof. A few evergreen central Texas native plants might be employed for this task (i.e sedges, cacti, beargrass, yuccas, or sotols), but given that the rooftop is a highly unnatural environment in the first place, why not drop the whole environmental restoration model? This challenging manmade environment is more like a hot, rocky mountainside in the Sierras of Mexico than like central Texas. A number of Mexican succulent plants like agaves, opuntias, sedums, hen and chicks, or purple heart (Setcreasea sp.) would be workable plants for Austin green roofs, as would South African bulbines or iceplants and Argentine Puya. All of these plants are attractive, evergreen, drought- (and deluge-) tolerant plants that naturally resist burning. I love native plants, prairies, and green roofs, but don’t think it’s always a good idea to put them together.
Scott, thanks for commenting. You make an excellent point. They say Austin will have even more wildfires in the future, so that should be a concern regarding green-roof plantings. Do you know whether Southern California has an established green-roof movement and whether they’ve adapted to the fire danger with appropriate plantings? —Pam