Q: There are so many different green roof systems. Are they all effective?

A: It’s easy for us plant enthusiasts to be seduced by the idea of verdant rooftops. Aesthetically, living roofs are a major improvement over typical asphalt or tar roofs, which are about as hospitable to humans and most other life forms as Death Valley on a mid-summer day. But before falling head over heels for green roofs it’s worth asking whether they really, as touted, help insulate buildings and thus save energy that would otherwise be consumed for heating or cooling, counteract the urban heat island effect, remove particulates from polluted air, detain and cleanse storm water, and more.

Green roofs certainly seemed too good to be true to Steve Windhager, director of landscape restoration at the Lady Bird Johnson Wildflower Center, and his colleagues, so they compared the performance of six extensive green roof systems from six different manufacturers to each other as well as to traditional non-reflective blacktop and somewhat cooler reflective white roofs. The study was conducted on hot tub-size mini roofs, each 30 square feet. Each of the test green roofs was planted with the same 18 native plants chosen for their wide tolerance of both drought periods and saturation after rainstorms, and the plants were provided with the same amount of irrigation when necessary.

Steve and his colleagues were surprised to find that there was a wide variation in performance among the different green roofs. They were much better at preventing the temperature of the air below from spiking on warm days, compared to both the conventional and reflective roofs. But while some of the roofs were able to capture a lot of storm water, others weren’t significantly better in this respect than the white or blacktop roofs. And while some of the roofs had nearly no adverse effect on water quality, others were worse than the typical suburban lawn—the more fertilizer in the planting medium, the worse the water quality, although after the first growing season, water quality dramatically improved. In short, no one system excelled at providing all the benefits conventional wisdom says green roofs are supposed to provide.

The Wildflower Center’s research is important in part because although a host of studies have been done on green roofs in temperate environments, Austin’s climate is significantly drier, hotter, and more prone to flash flooding than other study locations. To what extent does the Center’s research apply to other regions and climates? “I think that the storm water retention numbers will be pretty uniform no matter where you go,” says Steve. He adds that the study of green roof performance in Austin’s subtropical climate is useful “particularly if we are seeing a warming trend in our more temperate climates.”

When asked what advice he can give other public gardens considering green roofs, based on the Wildflower Center’s research, Steve pointed out that it’s important to determine why you want a green roof,  then make sure that a green roof is the most efficient way to achieve your goals. Once you have decided that you’re going to pursue a living roof, make sure the manufacturer you’re working with is aware of your goals. “Green roofs can certainly be designed to capture storm water, have clean runoff, provide energy savings, and provide valuable additional gardening space,” Steve says, “but these expectations need to be made explicit at the outset of the project or it will have an unfortunately high chance of not achieving all of these goals.”

Q: What is a green exhibit? How green does it have to be?

A: A green exhibit isn’t necessarily one that tells visitors how your garden is becoming more sustainable and how they can, too (though that’s a good idea!). Exhibits of all types and sizes can be beautiful expressions of sustainability. As for how green to go, you should make your exhibits as green as you can, and keep growing greener.

By now, most people in the public garden world are familiar with the LEED guidelines, performance benchmarks, and rating system for green buildings. The same basic guidelines can also be used for creating a green exhibit.

Like a green building, a green exhibit is one that is designed to minimize the use of resources and the generation of pollution, including the greenhouse gases that contribute to global warming.

A good source of information specifically on greening exhibits is the Green Design Wiki a publicly created and accessible resource modeled after Wikipedia. The website is divided into four sections. The first covers choosing materials and finishes, such as plywood and paints, when designing and constructing an exhibit. It includes good background information and tips, but an even simpler way to choose green materials is to look for those that have been certified by an independent organization, like Green Seal or the Forest Stewardship Council. And don’t forget to consider the ecological footprint of ancillary products, like the food you’ll be selling to the people who come to see your exhibit. It’s worth noting that a 2008 study in the journal Environmental Science & Technology found that red meat is 150 percent more greenhouse gas-intensive than chicken or fish. Cutting back on the red meat and dairy products you sell can make an even bigger difference than offering locally grown foods.

A second major consideration is how to minimize the use of energy over the exhibit’s entire life cycle, from fabrication and transport to operation and breakdown. I’d add that since the whole idea of an exhibit is to attract visitors, often as many as possible, a big part of reducing energy consumption should be encouraging them to walk, bike, or use mass transit to come see it.

A third goal for green exhibit developers is “closing the loop.” Many special and changing exhibits at public gardens and other museums are one-shot affairs. No matter how important the message, interpretation as currently practiced often is basically a throwaway business. But in the words of Kathy McLean in “Environmental Considerations: Some Guidelines for Exhibit Developers,” “what if the furniture and crates could be reused for another exhibition? Museums can design for reuse by creating an exhibition furniture vocabulary—a modular standard for exhibit components—that can accommodate a variety of configurations and arrangements. Furniture could be designed in such a way that surface treatments and detailing could change with each exhibition.” It’s certainly possible right now to at least create exhibits with materials like paperboard and glass that can be recycled. Some standard exhibition materials, such as plastic laminates and acrylics, are not yet made of recycled materials.

A final section of the Green Design Wiki, on sustainable graphics and signage, includes links to a few green vendors, such as a printer certified by several groups, including the Forest Stewardship Council, and a company that prints banners and other products on material woven from recycled soda bottles using water-based inks.

Green exhibits often cost more initially. But in the longer run, conserving energy and reusing the components can offset the cost and may even save money!

Q: What is the Sustainable Sites Initiative, and how can public gardens use it?

A: In the past several years, the LEED^R program of the U.S. Green Building Council has become synonymous with sustainable design. The USGBC awards four levels of LEED certification for the design, construction, and operation of high-performance green buildings: Certified, Silver, Gold, and Platinum. This rating system has provided targets for public gardens and other institutions striving to go green.

One limitation of LEED, especially for public gardens, is that it currently is concerned primarily with buildings. It’s not surprising, then, that two public gardens, the Lady Bird Johnson Wildflower Center and the United States Botanic Garden, have teamed up with the American Society of Landscape Architects to produce the Sustainable Sites Initiative, the first program to develop guidelines and standards for sustainable landscapes.

“The Sustainable Sites Initiative will clearly communicate the social, economic, and environmental benefits of sustainable landscape practices,” says Heather Venhaus, the Wildflower Center’s SSI program manager. It will not only provide specific sustainability benchmarks and targets for public gardens but also, in Venhaus’s words, serve “as an educational tool for visitors illustrating the positive impact they can have in their own landscapes.”

The Wildflower Center, USBG, and ASLA have partnered with a variety of stakeholder groups and a voluntary group of professionals who provide technical expertise on five subcommittees that cover the SSI’s major areas of focus: Hydrology, Soil, Vegetation, Materials (which includes maintenance issues like green waste and the use of chemicals), and Human Well-Being. The U.S. Green Building Council, one of the stakeholder groups, anticipates that once the SSI standards and guidelines have been developed, they will be incorporated into LEED.

 The SSI will consist of three “products.” A draft Standards and Guidelines report consisting of best practices for sustainable landscapes, divided into the five major categories listed above, is now available on the SSI website.

The next step is producing a Rating System, as in LEED, in which sustainable landscape benchmarks are assigned weighted credits, and an award or other recognition system with various levels of sustainability achieved is defined. This will be followed by a phase in which the Standards and Guidelines and the Rating System are tested in a number of pilot projects. The knowledge gained in these real-life examples will be incorporated in a Reference Guide to demonstrate how the credit system works and to aid creative problem solving.

One of the most innovative features of the SSI is that its standards and guidelines are based on the “ecosystem services” that landscapes provide — natural processes such as crop pollination by bees, birds, and other animals. Flood protection, air and water filtration, and greenhouse gas regulation by the soil and vegetation are among the other natural landscape functions that the SSI aims to protect or restore. These processes are essential for both healthy ecosystems and healthy human communities.

Sounds good, but what will this really mean in practice? In the future, the SSI is likely to guide public garden collections and landscape displays in a number of intriguing ways. 

The collections of most public gardens have long reflected traditional garden aesthetics and plant systematics. This has resulted in features such as formal herb gardens and herbaceous flower borders, as well as collections that focus on taxonomic groups, like cycads or orchids. Taxonomic collections often serve a scientific purpose, and traditional design elements are an important part of our cultural heritage, so these are highly unlikely to disappear, although the SSI will no doubt result in ornamental plantings that are more regionally appropriate — less reliant on irrigation and fertilizer, for example. Ray Mims, the U.S. Botanic Garden’s SSI representative, likens these traditional landscapes to the Old Masters at art museums. An art museum upgrading to a more energy-efficient HVAC system wouldn’t get rid of its Old Masters, he says, but rather “adapt the system to the appropriate humidity and temperature.”

However, the SSI’s focus on achieving ecological goals is likely to lead to new types of plantings and collections based on natural models in the regional landscape. One important ecological goal, for example, is protecting or restoring the area’s natural hydrological cycle. In a natural landscape, plants, along with the soil, absorb rainfall, so there is generally little runoff. By contrast, in our built environment we have radically altered the natural hydrologic cycle, destroying wetlands and replacing natural vegetative cover with roofs, paved paths, parking lots, and other impermeable surfaces. As a result, huge volumes of storm-water runoff flow in to storm sewers, carrying pesticides, motor oil, and other pollutants to nearby streams and rivers, fouling surface waters and destroying aquatic life through sheer physical force.

What kinds of landscape designs and plantings aimed at restoring natural hydrologic function can we expect as SSI increasingly exerts an influence on public gardens? Rain gardens, green roofs, and green walls, modeled after local plant communities that survive in similar conditions, are among the features likely to become prominent elements of the 21^st century public garden. At the moment, many of these sustainable design features are still being created by engineers, restoration ecologists, and others concerned more with functionality than beauty. Public gardens have the opportunity to transform ecological functionality into a new art form, creating spectacular green roofs, wetland gardens, and other sustainable plantings that wow their visitors and inspire them to grow these new ecological gardens in their own homes and communities.

Now a new movement called Meatless Monday is gaining traction. The goal of the campaign, which is being promoted in association with Johns Hopkins’ Bloomberg School of Public Health, is to reduce meat consumption by 15 percent to improve personal health, reduce our carbon footprint, and conserve resources like fresh water and fossil fuel. Last month Ghent, Belgium became the first city in the western world to go meatless once a week, although they’re doing it on Thursdays instead of Mondays.

On the Meatless Monday website, you can find information on seasonal fruits and vegetables, including recipes, check on who’s going meatless, and take the Meatless Monday pledge yourself.

Baraboo is a small city in south central Wisconsin with a population of less than 12,000. The surrounding Baraboo Ranges are all that remain of one of the most ancient rock outcrops in North America, composed of Baraboo Quartzite, a metamorphosed form of sandstone that originated about 1.85 billion years ago in what geologists call the Early Proterozoic Eon. The Baraboo area is also the terminal moraine of the Wisconsinan, the place where this final glacier of the last Ice Age dumped its debris, creating impressive sights like Devil’s Lake Gorge, where quartzite blocks crunched up by the ice sheet cling tenuously to steep slopes.

It was in Baraboo in 1884 that the Ringling Brothers began their circus, a band of oddballs if there ever was one. Over six seasons, the circus expanded from a wagon show to a railroad show with 225 employees, touring cities across the United States each summer. Baraboo remained the circus’s headquarters and wintering grounds until 1918.

A few years later, in 1924, Aldo Leopold arrived in nearby Madison, and in the early 1930s he purchased a dilapidated chicken coop and a few hundred acres of Dust Bowl-ravaged land near Baraboo as a weekend retreat for his family. At the shack, as it was called, Leopold was inspired to write conservation classics like A Sand County Almanac, launching the fields of restoration ecology and land ethics. 

The Baraboo Ranges continue to work their magic. A couple of years ago, about a mile down the road from the shack, the Aldo Leopold Foundation built the Aldo Leopold Legacy Center. The second highest-rated LEED Platinum facility to date, the Legacy Center also meets the 2030 Challenge, which aims to rapidly transform the U.S. and global building sectors from the biggest single contributor of greenhouse gas emissions to a central part of the solution to the climate crisis by changing the way buildings and developments are planned, designed, and constructed. 

The Legacy Center also happens to be the first carbon-neutral building certified by LEED. The initial carbon budget for the facility was based on projected emissions from combustion (including stationary sources such as wood-burning stoves and fireplaces, vehicles driven by employees to and from and at work, and estimated visitor vehicle use); on-site electricity generation from photovoltaic cells; wind-generated electricity purchased at night and on days when the solar array does not meet building demand; and carbon sequestered by the Foundation’s 500 acres of forested land. You can find out more about how the Center reduces and offsets its carbon emissions here.

The beautiful facility is located on the land where Leopold perished in 1948 while fighting a brush fire on what was then a neighbor’s property.