Posted: 16/06/2013 at 15:55
Geoff Hamilton used to make his cementitious products with something he called Hypertufa. Just type hypertufa into google and the search box should show various options as you type the name such as hypertufa recipe, hypertufa moulds (spelt the American way ) etc. [just had a look and there are 10 options].
I've also heard of mixing cow manure with a cement mix and throwing it rough cast in a haphazzard sort of way onto a concrete block wall as a sort of rendering. Plants such as wall flowers will then grow in the dried mix and make itv look completely natural. Must admit though, I've never tried it!
There is a you tube video you acn watch on making hypertufa as well