By Anncr
United Kingdom 
i have a stone retaining wall in my garden which has a supporting concrete buttress running its full length which means the soil above the wall for the first 12" is only about 2" deep. I would like something that would tumble over the wall - is there anything that would tolerate such a poor layer of soil or must I plant things further back and just encourage them over the edge!?
10 Jul, 2011
Answers
Dalmation bellflower (Campanula Portenschlagiana) could look beautiful - they tolerate poor moisture and love walls.
10 Jul, 2011
Thanks for those suggestions - the wall faces north/west and is only about 36 inches tall, there is a good sized pear tree growing on the ground it is supporting.
I will try to sort out a photo!
11 Jul, 2011
Try fuchsia Lena for one section, a beautiful hardy plant and a lax grower that would hang down over the wall a little way even if planted 12" back. (Only from midsummer until the frosts though) It would leave you with a bare patch for the other half of the year but you could plant bulbs up close to it.
11 Jul, 2011
Previous question
You could try very shallow rooting things such as Sempervivum, althoughthey don't trail very far! Try things such as climbing Nasturtiums in the deeper areas and train them in the right direction. You don't mention whether the site is in sun or shade, this would help with suggestions. Add it as an 'answer' underneath this comment and we can continue.
10 Jul, 2011