West Linn Landscapers West Linn, OR

Northwestern homeowners go vertical with gardens

Living walls resemble a garden, in that the initial plant size and spacing is not necessarily indicative of how the wall will look a few months after the installation.
Photo courtesy of SolTerra Systems

by Pat Munts

The move to more "green" building practices is changing how we think about gardens. Traditionally, plants merely decorated the yard and little more. Now, green roofs and living retaining walls are a powerful ally in our sustainable efforts.

Green building advocates Donna and Riley Shirey incorporated living walls when designing their new house in the Seattle area. Constructed on a 65 percent slope, the living walls help to stabilize the ground. "Adding green walls to slow down the water running off the site just made sense," Donna says. The Shireys implement their green beliefs at their sustainable building and maintenance company, highly rated Shirey Handyman Service in Issaquah, Wash.

Living retaining walls are often long tubes of porous material filled with soil, stacked on top of each other across a slope and tied together with geotechnical fabric. The fabric is then run back into the bank to anchor the wall.

The Shireys planted their wall with wild strawberry and other vining and trailing plants that will fill in over time. The tubes can also be hydroseeded with grasses and other small plants. The plants then grow out, covering the tubes completely. The cost isn't much different than that of a traditional concrete wall, according to Shirey, running from a few hundred dollars to several thousand depending on the location, size and complexity.

Vertical green walls in a garden can manage runoff and, in addition, provide a sound barrier for ambient urban noise, cool the air on a hot day and provide a habitat for birds. Green walls on and in buildings can help reduce heating and cooling costs and clean particulates out of the air.

Vertical walls consist of porous, felted-fabric pockets hung on a frame and planted with plants suited for the wall's location. A pressure compensating drip irrigation system set on a timer waters and administers liquid fertilizer to the garden. "They are basically a hanging garden," says Matthew Thomas of SolTerra Systems, a design and build firm that specializes in innovative energy solutions with roofing, solar electricity, green roofs and living walls in Portland, Ore. "And as such, they're like any other garden bed."

Maintenance of a living wall isn't much different than maintaining an average garden bed. Plants need to be watered regularly, trimmed and pruned seasonally, vigorous growers trimmed back and a few replaced. Proper fertilization of plants in vertical green walls is probably the most crucial issue. "The wall turns into a somewhat hydroponic system after the original nutrients leach out of the soil and need to be replaced regularly," Thomas says.

The structures holding up vertical living walls need to be sturdy but typically don't need a lot of reinforcement to handle the weight. Thomas says the most important element of a vertical wall is to properly waterproof any structures behind them. "This can be done by applying waterproof wall material, paint or even pond lining to protect the surface," he says.

Pat Munts grew up in western Washington but has spent the last 30 years gardening on the dry east side of the state near Spokane. She freelances for the Spokesman-Review and has served as eastern Washington editor for Master Gardener Magazine. She's the small farms coordinator for both WSU Spokane County Extension and the Spokane County Conservation District.