High soil pH and urban soil composition is the reason the Jacksonville Whole Foods living walls are not flourishing. Soil pH is a measure of acidity or alkalinity in the dirt.
As we mentioned, 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 site could easily be supporting massive amounts of flowering, fruiting and beautiful vines by mid summer 2012.
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.
With amended soils in place, plants can now be chosen to highlight the wonderful health food selections available within the Whole Foods store.
Selecting beautiful, sometimes unusual and otherwise ethnobotanically important plants is the fun part of site living wall design.
Our next post will describe what plants we'd suggest for the Whole Foods living walls.