Green walls are "it" accessories in the sustainable design world. But a planted wall that doesn’t stay green is neither beautiful nor sustainable; reinstalling or swapping out such a feature wastes materials and money.
Making sure that the green-wall technology worked was especially important for Longwood Gardens, a former Quaker farm and DuPont estate in Kennett Square, Pa. A constant stream of visitors expects to be wowed by a variety of flora, and environmental stewardship is an important part of Longwood Gardens’ mission. The green wall in the institution’s new East Conservatory Plaza, designed by British landscape architect Kim Wilkie in association with Philadelphia’s Wells Appel, is the largest in North America, at more than 4,000 square feet.
Fortunately, the installers at interior landscaping firm Ambius have worked on green walls almost as long as the technology has existed—about three and a half years, long enough for senior project manager Denise Eichmann and her colleagues to learn a lot by trial, error, and close study. “You can’t just install these systems and walk away,” she says. “When you’ve lived through different cycles and seasons, you gain a lot of knowledge.”
The biggest challenges in a green-wall project are water and light, both essential to plants’ survival. Water can accumulate at the bottom of a system, says Ambius construction manager Mark Hawry, inundating some plants while leaving those in higher sections dry. Detailed light studies are needed early in the design phase, says Eichmann. The information ensures that appropriate plants are specified and that the irrigation system delivers the right amount of water to keep them thriving.
The Ambius team is sold on the approach developed by Vancouver, Canada–based GSky Plant Systems. Stainless steel panels, generally 1 foot square but customizable, are mounted on a stainless steel frame attached to the wall; they can be removed for inspection or adjustment. Prior to installation, bags made of landscaping fabric and filled with a proprietary non-soil growing medium are placed in the panels, and the plants are grown off-site, but horizontally, in conditions that mirror those of the green wall. The young plants acclimate as they grow and their roots intertwine with the fibrous medium, knitting the system together for vertical stability. When Longwood Gardens’ wall was installed in October, the 47,000 plants, mostly ferns, were securely established.
Eichmann and Hawry also like GSky’s irrigation technology. Some systems run a single drip line over the top of the wall, but GSky runs lines through every panel; irrigation zones are determined by site conditions and plant layout, says Eichmann, and flow rates can be adjusted from .5 to 3 gallons per hour, as needed. GSky also provides 24/7 monitoring via a network of sensors embedded within the growth medium, helping ensure that a green wall stays verdant.