On mortar and concrete, sometimes on bricks or other artificial substrates, also on sandstone rocks, always in ruderal and nitrophilous conditions.

Belgium: Mar.: RR, Fl.: R, Camp.: R, Brab.: RR, Mosan: RR, Ard.: RRR.

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

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

Lit.: Boul.: 69, NL84: 14, NL92: 170, NL93: 44, van den Boom (1992: 238-240), Zwaenepoel et al. (1994: 37).