Over the years we've come to understand Living Walls to be one of the most significant challenges for the urban core landscape designer, and for many reasons.
Living walls, unlike horizontal ground level landscapes are subject to exponential more desiccating exposure from winds because they exist on a vertical plane without typical ground level wind-breaks. Additionally, the same holds true for sunlight exposure. Both sunlight and wind can rob the living wall plants of much needed water, thereby breaking the Calvin cycle of photosynthesis and denying the plants life sustaining nutrients.
Last year we posted an article on why we consider wind and light to be the two top design factors for green roofs and living walls.
Too much or not enough light dooms a living wall plant through impact on photosynthesis, yet even though there was concern raised about the quantity of available light under the store's front area, the southern facing living wall, with plenty of light exposure, was not growing either. Our model pointed to issues other than available daylighting.
Wind too, though usually a primary design variable, did not seem to be impacting the living wall as we first thought it may. Our hand held anemometer, though granted was used over a limited period of time, did not record any wind speeds of greater than one meter per second and in fact showed the building itself was acting as a sufficient windbreak.
However there are other factors to consider when analyzing the Whole Foods dead living wall. A secondary design variable we often look for is the presence of alleloism and adjacent allelopathic plants, such as cypress.
We did not find much to suggest allelopathic issues on the site, though allelopathism can sometimes be overlooked. Chemicals produced in the leaves of some plants can act just like herbicides, preventing other plants from growing. Sometimes allelopathic acting leaves may accumulate on a roof and act as a herbicidal drench during rain as water fills gutters and downspouts.
There was a more interesting issue presenting itself though. Though living walls have been grown successfully around limerock outcroppings and stone walls, the correct combination of soil amendments, plant selection, light, available water and wind breaks must be present for the growing successes a landscape designer seeks.
The Whole Foods living wall systems were constructed directly over an old, demolished commercial building foundation and though some organic matter has been added by the landscape installer, the urban soil composition on site is obviously full of concrete.
Concrete contributes to a high pH. High pH restricts available nutrients and itself has a negative impact on plant root's ability to absorb water. However some plants are very well adapted to growing in these higher pH conditions. Yet many are not.
|Living walls can successfully be created even in rock & concrete filled areas|
|Plants and concrete can exist side by side with the right design|
Understanding urban soils, concrete and how to amend these soils for the right plants comes with years of experience.
Though we are all aware of cost control, long term dead living walls installed without consideration to matching plants to all growing variables do not provide the cost benefit originally proposed during the architectural and landscape design.
Whole foods has many options available to produce magnificent living walls for the Jacksonville store.
In sync with cradle to cradle concepts, Whole Foods could, once the right plants were installed in the correctly amended soils for the light levels and wind exposures, use a compost barrel in back of their store - or as an educational part of their landscape - and use produce destined for the landfill to begin building wonderful planter soils. Solutions do not have to be messy or expensive. Living walls create habitat for Florida green tree frogs and Florida anoles. Biodiversity acts as integrated pest management for fly and bug control.
Why are Whole Foods living walls dying?
Wrong plants for the urban soils. Urban soils needing specific micronutrients and other factors.
Next post will discuss specific recommendations to create a lush living wall.