On hard calcareous rocks in highly nitrophilous conditions, common on artificial substrata like concrete, mortar, etc.

Belgium: Mar.: AR, Fl.: AR, Camp.: AR, Brab.: AR, Mosan: C, Ard.: AC (only on walls and asbestos in nitrophilous situations, especially in farms), Ard.: RR, Lorr.: AC.

Luxembourg: Ard.: RR, Lorr.: R.

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

Lit.: Boul.: 67, Ertz: 19, Ma: 167-170, NL92: 150, NL93: 42, VGH: 114, Zwaenepoel et al. (1994: 37).