Gardening Methods

I have a flat stone rock wall which requires weeding from time to time throughout the summer. I want to plant?

flowers in the spaces the weeds grow. I know there is minimal soil there because grasses and weeds sprout from time to time. I was thinking to blue lobelia flowers (http://images.google.com/imgres?imgurl=http://image60.webshots.com/460/0/74/67/2406074670079267387QhPJnx_ph.jpg&imgrefurl=http://home-and-garden.webshots.com/photo/2406074670079267387QhPJnx&usg=__IFMj6haCnO5R1Q7CmehpHfCon14=&h=600&w=800&sz=241&hl=en&start=4&um=1&tbnid=4JnhCgDzx1vHOM:&tbnh=107&tbnw=143&prev=/images%3Fq%3Dlobelia%2Bflowers%26hl%3Den%26sa%3DN%26um%3D1) and white alyssum (http://www.flowers.vg/flowers/alyssum01.htm).
Do you think the flowers could be grown in a rock wall? Is there anything special I would need to do other thsan water them?
I don’t want to cover the wall, just accent it. My husband built the wall and we love it.

Allysum is a good choice but not so sure lobelia would like the dry conditions. Why not try alpines in the holes. They love these sort of conditions and will thrive. Groundcover sedums would be my first choice but there are many more. Check these links.
http://www.alpinesandgrasses.co.uk/AlpinesSRWchoice2.jpg
http://www.pottertons.co.uk/pott/browse.php?folder=246

Rock Climbing Eldorado 1 of 5 Route T2 Red Garden Wall