This couple is the author of the book ‘Green Roof Plants’ (ISBN 978-0-88192-787-0). It includes photographs and cultural information about more than 200 species and cultivars including data about heat tolerance, moisture needs, hardiness and so on.
This practical handbook is a valuable resource for anyone interested in the subject and covers it all; from roof construction and plant selection to soil medium and maintenance.
In combination with solar (photo-voltaïc) energy a roof garden with its insulating qualities can, especially with the South African power outages, contribute to significant less dependence of public electricity supply and less energy use for cooling (in Summer) and heating (in winter).
The book can be ordered in any ordinary bookshop or, online, via Amazon.
The blogsite of Urban Habitats is also a useful source for people who want to know more about roof gardens.