INDIGENOUS VEGETATION FOR CRB WALLING – THE ROUTE TO GO ADVISES THE CMA :

However, the Concrete Retaining Block Division of Concrete Manufacturers Association (CMA) cautions that unless indigenous plants are cultivated the amount of maintenance required to keep CRB vegetation alive is likely to be expensive and time-consuming.

“Exotics require far more attention than indigenous plants which are largely self-supporting once established,” says Silvio Ferraris, CMA president and vice president of its CRB Division.

“We often field calls from professionals and property owners who voice disappointment that the wall vegetation planted by them is not performing as they had hoped. Invariably the reason is that they have opted for exotics, which are not suited to local climatic conditions.

“South Africa has a rich botanical heritage and there are numerous plant varieties which are suited to CRB walling. Indigenous plants adapt easily to prevailing climatic conditions and generally require less watering. Moreover, many are deep-rooted and offer the added benefit of enhancing the strength and durability of the wall itself.

“Although genetically programmed to withstand the vagaries of local conditions, indigenous plants still need careful selection in a country as large and diverse as South Africa. Factors that need to be taken into account before choosing what to plant include climate, coastal conditions such as salt-laden winds, as well as exposure to sunlight and shade.  Others, such as soil fertility, irrigation, and maintenance requirements such as pruning, are also important considerations. A good rule of thumb is that herbaceous deep-rooting plants tend to require minimal maintenance, whereas the converse applies to attractive flowers.

“The retaining wall itself should be designed for maximum structural mass with no air voids and should provide optimal rooting conditions. This will help bind the retaining wall and the embankment,” advises Ferraris.

CMA director, Hamish Laing, comments that the establishment of wall gardens is an important element in the creation of sustainable environments.

“Sustainable, eco-friendly structures should be the concern of every architect, landscape designer, civil engineer and property developer. Wherever possible they should pursue the eco-friendly route, whether in the establishment of indigenous CRB wall gardens, the building of attenuation ponds or the laying of permeable paving,” says Laing.

There are essentially four planting regions in South Africa,  Coastal, South Western Cape, Highveld and Lowveld, each with its own set of climatic conditions. Most indigenous plants are suited to all regions, however, roughly half are ill-suited to the Lowveld. Rainfall patterns are also important as water requirements differ from plant to plant.

These and other facts related to CRB wall gardens are covered in a booklet, Terraflora™, published by CMA member, Terraforce.  Besides covering the information already discussed above the booklet provides tabulated information on each climatic region, including plant types (giving both the Latin and common names), as well as sun and water requirements.

Copies of the booklet are available from Silvio Ferraris (Teraforce Gauteng licensee) on 011 393-5504 or 082 8519512 or from Karin Johnson at Terraforce on 021 465-1907 082 5567997.

An example of indigenous plan growth on a retaining wall at The Island, an exclusive residential development situated at Hartebeespoort Dam.

A profusion of indigenous plant growth thrives on this retaining wall situated in Bankhoek near Stellenbosch.

DATE : July 2010
ISSUED BY : David Beer Communication Consultants
FOR : Concrete Manufacturers Association 
ENQUIRIES : Hamish Laing (011) 805 6742
Silvio Ferraris (011 011 393-5504 or 082 851 9512
David Beer (011) 478 0239 or 082 880 6726.  Email: bigsky@ibi.co.za