This is an interesting and very practical idea developed by Gösta Nilsson, the Director of Sanitas in Botswana. He has developed a container gardening system based on walls with built-in growing boxes, made of hollow concrete blocks. The blocks are made using a simple, hand-operated block-making machine. With such a machine, two persons can make 100 blocks a day from a mix of 1 part cement and 4 parts sand. This is the size block which is used at Sanitas, but blocks of similar size would be fine...
millimetres
When building the wall, some of the blocks are turned sideways. The hollow part which is exposed, is given a floor and a hole for drainage. You may find it easier to add this floor and drainage hole when casting the block. (Some block makers produce blocks with slightly tapering sides and a thin base.) The core of the wall is filled with a very weak concrete mixture (for example 6-10 parts sand or gravel to 1 part cement). The exposed containers are filled with sand on top of a thick layer of manure. The containers are then ready for planting.
The containers can be arranged in various patterns and the wall can be provided with containers on one or both sides. Experiment with small blocks of wood to work out a suitable design. In one interesting variation, just a quarter of the container block is projecting on each side of the wall. These overhanging blocks require floors (but no drainage holes).
The whole wall is then filled with growing medium (sand and manure). This means the roots have access to a larger area as they can grow into the unturned row of blocks as well. Water can trickle down inside the wall from top to bottom.
Watering can be done either by hand or by laying a hosepipe with small holes made about every 20 centimetres along the top layer of the wall, and connecting to a tap (drip irrigation). Regular watering is essential, as walls will dry out more quickly than garden soil.
These growing walls would be ideal around compounds, or along the edges of balconies in cities. In dry areas, it might even be possible to use this idea for the building of outer walls of houses or workshops (care would be needed to prevent damp inside the building). They would make it possible to grow vegetables in a very small space.
Details of how to make a simple block-making machine and lists of manufacturers are available from...
BASIN GATE, c/o Mrs H Schreckenbach, Section 402, Postfach 5180, D-6236 Eschborn 1, Germany
or from...
Otto Ruskulis, ITDG, Myson House,Railway Terrace, Rugby, CV21 3HT, UK.
With many thanks to Gösta Nilsson and SIDA for permission to include this article.