Green Roof and Living Wall Soil Media - Vertical Green Begins Below Ground

Vines provide great vertical screening and greening capabilities, especially here in Florida where strong desiccating winds can quickly overwhelm and dessicate a planted exterior living wall,

Coral honeysuckle, Lonicera sempervirens offers interesting color and texture as a living wall

 (unless one uses a non-native invasive species like Boston Fern, Nephrolepis cordifolia, which is never recommended).

One of the most important aspects of creating a beautiful, thick and lush living wall is sometimes never even considered, that being the quality and characteristics of the soil in which the vines are planted.

Unfortunately, many designers only consider the flowers or foliage, forgetting the roots though not seen, are so critical to leaf and flower development.

Native Carolina jessamine, Gelsemium sempervirens should be nice and thick but is planted in bad soil

In urban development projects the soil can be concrete rubble with a high pH.  In situations like these a beautiful stainless and expensive trellis and nice, hot house grown plants can end up looking terrible in a matter or weeks.

Coral honeysuckle planted in poor soils looks terrible

I've written about the Jacksonville Whole Foods living wall trellis system before - an expensive living wall system that looks pitiful, all due to high pH and other soil problems.  Soil pH is a measure of acidity or alkalinity in the dirt.

Living wall vines can become woody without proper soil, loosing their leaves

The health food grocer has a high-quality stainless trellis system installed near the front entrance and on the south side of the store building.  Yet the plants have not successfully established themselves and grown well.  The store has been open now for several years, allowing plenty of time for the plants to send down roots and add  upper biomass.

The present store facility was originally constructed where another building had been demolished.  It appears some of the original slab was reused, and significant amounts of concrete, crushed block and other previous building material was integrated into the soil during site preparation.

Most plants prefer a soil pH of between 5.6 up to 7.0.  Many native and adapted Florida Friendly plants vines require an even lower pH to thrive.

Soils with a high pH, such as the urban soils in the Whole Foods living wall planters, restrict nutrient availability (specifically iron, zinc and manganese), stunting planted vine growth and causing yellowing of leaves.

Although some soil amendments appear to have been added during final landscaping, the type and quantity were not adequate to encourage strong plant growth.

There are several simple remedies available to the Whole Foods site.  The living wall was installed in 2010-2011 and could have easily be supporting massive amounts of flowering, fruiting and beautiful vines by mid summer 2012.  Today it is 2014 and the vines still struggle to maintain a tiny about of leaf cover.

But a remedy is possible.  First there needs to be a minor excavation of existing planter soil, both around the front columns and then within the southern wall planter box.  This soil does not need to be discarded.

Second, an appropriate amount of ammonium based fertilizer should be mixed into the soil.  Ammonium based fertilizers typically contain ammonium sulfate or sulfur coated urea.  Ammonium and oxygen react to form nitrite/nitrate, water and hydrogen ions.  The hydrogen ions then work to acidify the soil.

One advantage urban soils usually have is the variety of soil particle sizes and if not over-compacted, can provide for adequate oxygenation of the soil.  Oxygen and ammonium provide nutrients for the plants and help counteract the higher pH of the urban soils.

A quick field test of the Whole Foods planter soils reveals significantly higher than normal  pH.

Amending with organic matter is another possible approach.  Composted pine bark, pine needles, oak leaves, properly composted food scraps can also release both needed nutrients and hydrogen ions into the soil.  Another benefit of the organic mulch route is that earth worms and other soil life will quickly create extensive micro-communities, contributing additional nutrients and providing for nature based soil aeration.

Once the Whole Foods planter soils are amended with the proper amount of ammonium based fertilizers, the soil can be replaced and plants installed.

Of course, care should be taken not to over-fertilize.  Excess amounts of ammonium based fertilizers can burn the roots of installed plants, creating a whole new set of problems.

Native and landscape vines alike can add vertical interest, privacy, screening, color and texture to a landscape project under almost any atmospheric conditions if they are growing in adequate soils.

Remembering that vertical green begins far below the ground is the first step to living wall design and construction success.