On calcareous, naturals outcrops, also found on walls, concrete, etc.

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

Luxembourg: Ard.: RR, Lorr.: AR.

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

Lit.: Boul.: 69, L5: 23-24, NL84: 14, van den Boom (1992: 245-247).