The Wallflower or Cherianthus cheiri is so called because it will quite happily grow out of a wall and is often found thus.
Presumably it was around before walls were invented so its natural habitat would be cliff faces and mountain sides.
There are many other plants which have a similar pedigree and I find them particularly attractive. In this part of France there are many ancient buildings and as long as they have not been repointed too recently one can often see wall flowers of various types enhancing the stonework. Actually to be 100% correct I should say wall plants because quite often different types of ferns live in this situation and of course as we all know Ferns are not flowers they are Pteridophytes.
If you are unsure what a certain wild flower is then have a look at my pages on wild flowers of Poitou-Charentes, it may help.