Posted: 07/11/2013 at 12:16
Things you'll have to factor: How you will get to your plants. How to water your plants and keep them irrigated (could you use rainwater from the gutters, or pump it?). How to avoid damaging the property with water ingress, or heavy loads. And the aspect of the wall will play a part in your planting.
Note that vertical training of plants/trees such as espaliers has been around for a long time. And some people grow in hanging baskets, and some people plant their tomatoes upside down.
I'd be interesting in hearing planting choices? What are you thinking of planting: salads?
Vertical planting is becoming more popular, I've mostly seen succulents. Search for 'vertical planting succulents'. Even growing somethnig like ivy can act as an insulator for a building. Also note that walls can provide some heat retention.
Succulents don't need much in the way of a growing medium. I think the greatest challenge is getting around the load issues. You can use less soil, and more fertiliser (hydroponics), but then you might end up fighting water loss. Some might not like the idea of using artificial fertilisers.