On mortar of old walls, on stones, and on natural, sandstone and siliceous outcrops in exposed and sunny conditions.

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

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

France: Mar.: R, Boul.: R, Pic.: R, Mosan: RRR, Ard.: RRR, Lorr.: RR.

Lit.: Boul.: 69, La69: 104, Mü1: 151, NL84: 14, NL92: 170, VGH: 114, Zwaenepoel et al. (1994: 37).