On cement of calcareous walls in highly nitrophilous conditions (e.g. around farms), rarely at the base of natural sandstone rocks in forest.

Belgium: Mar.: AR, Fl.: AR, Camp.: AR, Brab.: AR, Mosan: AC, Ard.: R.

Luxembourg: Lorr.: RR.

France: Mar.: RRR, Boul.: RRR, Pic.: RRR, Lorr.: RRR.

Lit.: Ma: 216-218, NL84: 12, NL93: 42, VGH: 114, Hoffmann & Van Rompu (1995), Zwaenepoel et al. (1994: 37).