Opening Statement:

Green walls are not new. French botanist Patrick Blanc has been popularizing green walls by building awe inspiring, hydroponically fed, wall structures since the late 1980s. But are they really sustainable? Do the benefits outweigh the costs? And has the technology evolved to a point where homeowners can reasonably install a useful vertical garden in their homes?

The Prosecution’s Case:

Large-scale green wall systems are expensive, but without them structural damage can be incurred to the building, and plants can easily suffer from drying out too fast and limited growth due to size restrictions on the roots. The hydroponic systems that are commonplace are often not sustainable as they tend to support plants that would not be able to grow with just natural rainfall, and they require substantial additional resources.

The Defense’s Case:

Green walls are the subject of fast moving technology developments with the goal of increasing transpiration and the
cooling effect of large walls, as well as reducing resources and expense. These systems are additionally being evolved
to use grey water and the condensation of HVAC systems, which will make them substantially more sustainable. For small-scale wall builders, green walls can provide planting space for homeowners who simply have none. Though requiring significant maintenance, they can be very effective for balconies, fences and railings; any garden area is always better than no garden area.

The Evidence and Facts:

• Vertical gardens dry out fast due to a lot of evaporation and are often fed through hydroponic systems.
• Just as with a regular garden, siting a green wall and planning for appropriate plants is imperative to success.
• Wall gardens get less sun than in-ground gardens.
• Long-term success of wall gardens must account for maintenance. Maintenance might include dealing with calcification that comes from irrigation scale, replacing plants, replacing soil, installing and repairing irrigation systems and repairing walls that suffer damage or grow mold due to overflow or poorly controlled water.
• Vertical gardens have fewer weeds than in-ground gardens.
• Vertical gardens provide options for planting where no ground square footage is available.

Witness Testimony

Shawna Coronado, Author of Grow a Living Wall, Create Vertical Gardens with Purpose:

“If vegetable gardening a living wall, the return on investment is calculated by the level of plants each living wall enables the gardener to plant and harvest. For less than 2 square feet of floor space it is possible to plant between 40 and 50 plants in the average six-foot-tall unit. Therefore, when calculating rates of plant return based on square footage, there is a huge return for a very small amount of space.”

“They require no weeding and are easier to water, particularly for members of the family who might have a more challenging time walking, bending, and lifting hoses through larger inground gardens.”

The Verdict:

A beautifully planted and maintained green wall garden is, without question, a gardening feat that deserves attention for its remarkable impact on it surroundings. They do offer cooling, particularly in urban areas where the heat island effect is strong. They are also artistic and they beautifully soften the architecture that they live on. But to consider them
as more than art and rather as a truly sustainable solution for greener cities would require further advances in technology, research, and design. The question of true sustainability remains somewhat elusive. It is estimated that a green wall that is 215 square feet in size offers the same environmental advantages as a medium sized tree. A medium sized tree is, however, much less expensive, easier to manage, and needs less water. As an option for creating a small-scale garden where a homeowner would not otherwise have the opportunity to grow plants or food, it seems that wall gardens open the door to new gardeners. They are not ideal, and they come at a fair price for installation and maintenance but they can still make a lot of sense. This mixed review leaves the jury hung.