How designers and botanists are putting a colourful flourish on drab urban landscapes

Mike Weinmaster and Patrick Poiraud have their own interpretation of “going green.” They mean it literally. The founders of Vancouver-based Green Over Grey Living Walls and Design plant herbs, flowers and even trees vertically on city buildings. “We wanted to integrate gardens in the middle of a concrete jungle,” says Poiraud, who has degrees in botany and ecology. His company just completed one of the largest vertical gardens in North America, a 2,680-sq.-foot green feast of more than 120 plant species covering the once dreary facade of the Semiahmoo Library in Surrey, B.C.

The wall does not contain an inch of dirt. The plants are inserted between layers of porous, synthetic fibre material that acts as a growing medium for the roots. The irrigation system ensures water, filled with minerals and other nutrients, circulates vertically, trickling down from top to bottom, where it’s collected and recycled.

Similar systems have been in development for decades—but for very different purposes than greening cities. As a researcher at the University of Guelph in the mid-1990s, Alan Darlington studied using vertical gardens as an air filter for Mars-bound spaceships. Growing plants vertically, he discovered, could provide astronauts on an 18-month round trip in outer space with a constant, space-saving supply of fresh air. Darlington, the founder of Nedlaw Living Walls, soon realized the system had applications here on Earth, too. His green walls include metal perforated pipes that draw air toward the plants’ roots, where bacteria break down pollutant particles more efficiently, acting as a indoor biological purifier, he says.

These systems, however, can be pricey, ranging from $110 to $400 per sq. foot. A much cheaper way to build green walls is with modular boxes, or pre-planted plastic and metal trays filled with dirt, hung on the wall. Making green walls available to the common gardener is the philosophy behind ELT Easy Green, a Brantford, Ont.-based company that marketed a do-it-yourself vertical garden kit for as little as $79. The system, says founder Greg Garner, is not only economical, but “fairly foolproof,” as potted plants are better able to withstand things like glitches in the irrigation system that could rapidly kill a no-soil garden (although critics of the modular technique say that hydroponic gardens, if properly cared for, last much longer).

With or without soil, living walls are energy efficient. They’re eligible for LEED points (a certification program for green buildings that’s tied to a variety of government incentives in Canada). Like green roofs, they can keep buildings warmer in the winter and cooler in the summer, reducing energy costs by as much as 20 per cent. Interior green walls also dampen echoes, reducing acoustic pollution. And many advocates say they’re a great antidote for the winter blues, providing relief from the greyest months of year.

In an increasingly urban world—the UN says 69 per cent of the Earth’s population will live in cities by 2050—growing plants up the walls may well become the only way to make the planet a truly greener place.