Dec. 15 2015 07:50 PM

Anyone who’s seen a stage illusionist knows the feeling—that tingle of surprise as something which you know can’t exist in nature appears right before your eyes.

We hunt for the trick, the hidden mechanism that allows the impossible to happen, often to little avail.

This is because the men and women behind these illusions put a truly enormous amount of work into accomplishing something that’s merely improbable. They work until the improbable becomes certain— and the reveal is then certain, every time.

Believe it or not, some landscape installers have a trick of their own, a novelty to the eye. These contractors are installing living walls, and showing their clients what plants can be grown on a steep—or even completely vertical—slope. With a little forethought, a contractor can amaze their customer, and the guests they entertain.

The most important thing to remember about living walls is that they are, first and foremost, walls. While there are some non-structural applications, like living fences, a kind of steel grid embedded with ivy, the most common application is a retaining wall with plant material embedded in it. The primary job of a retaining wall is to hold back earth, and so the design must be structurally sound, and have a plan for drainage or succumb to hydrostatic force.

The first benefit of a living wall is that it has a use for extra water built right in. The plant material has to be irrigated, and using the water that builds up behind retaining walls for that purpose kills two birds with one stone. Of course, that’s easier said than done, and in some instances, it may be simpler to set up a French drain for the wall and sprinklers for the plants, but porous retaining walls, or ones that feed into a catchment, can provide plenty of water for irrigation.

Living walls aren’t just impressive looking, they’re downright amazing. A traditional retaining wall, constructed of concrete or stone, can be a heat island. In hot climates, the infrared glow of a well-baked wall can make the surrounding area unpleasant or flat-out inhospitable. A sloped wall of plants, however, eliminates this effect, and instead brings all the improvements to a landscape that green and growing things usually bring.

“It’s green space; it’s habitat,” said Mark Woolbright, founder of the Living Wall Company in St. Louis, Missouri. “A living wall has the environmental benefits of noise reduction, and reduction of pollution from particles in the air. You’ve also got a thermal buffer, and it’s actually a tool for remediating urban heat island effects.”

That particular blend of benefits isn’t attractive to just the residential and commercial markets. Landscape contractors bidding on public sector design/build jobs can present living walls as a good option for environmentally-sensitive areas and eco-minded municipalities. A living wall was chosen as a substitute for riprap and Earth Images, Inc. was tasked with building it.

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